EMCEE Broadcast TTU500FA UHF LPTV Transmitter User Manual TTU1000FA Mnl Cover Pg 1

EMCEE Broadcast Products UHF LPTV Transmitter TTU1000FA Mnl Cover Pg 1

TTU500FA Users Manual

Broadcast Products

P.O. Box 68, White Haven, PA 18661 Phone: (570) 443-9575 FAX: (570) 443-9257

MDS MMDS ITFS LPTV

North America South America Europe Asia Australia Africa

Since 1960

6) USERS MANUAL

TTU500FA

SOLID STATE LDMOS

500W UHF TRANSMITTER

TTU500FA

SOLID STATE LDMOS

500W UHF TRANSMITTER

05/01

IMPORTANT

Transient Overvoltage Protection

Transient overvoltage of micro- and nano-seconds durations present on AC lines

are a continuous threat to all solid-state circuitry. The resulting costs of

equipment repairs and system downtime make preventative protection the best

insurance against these sudden surges. Types of protection range from isolation

transformers and uninterruptible power supplies to the more cost effective AC

power line protectors. As transients are most often caused by lightning induction

and switching surges, AC power line protectors are the most practical solution.

An effective AC power line protector is one capable of dissipating impulse

energy at a low enough voltage to ensure the safety of the electronic compo-

nents it is protecting. The protection unit should be across the AC line at all

times even during periods of total blackout. It should also reset immediately and

automatically to be 100% ready for repeated transients.

TABLE OF CONTENTS

I. THE TTU500FA TRANSMITTER

1.1 Introduction

1.2 Specifications

1.3 Installation

1.4 Operation

1.5 Warrant

and Parts Orderin

II. CIRCUIT DESCRIPTION

2.1 Modulator

2.2 EMEX1 2 Watt UHF Exciter

2.3 500 Watt UHF Power Amplifier

2.4 Output Section

2.5 Control/Meterin

Panel

III. MAINTENANCE

3.1 Periodic Maintenance Schedule

3.2 Recommended Test E

uipment

3.3 Troubleshootin

3.4 Ali

nment

3.5 Output Power Calibration

3.6 Linearit

Corrector Ad

ustment

3.7 Remote Monitor Si

nal Levels

3.8 Spare Modules and Components

3.9 S

nthesizer Pro

rammin

IV. DATA PAK

V. SCHEMATIC DIAGRAMS

SECTION I

THE TTU500FA TRANSMITTER

1.1 INTRODUCTION ....................................................... 1 1

1.2 SPECIFICATIONS ..................................................... 1 1

1.3 INSTALLATION ........................................................ 1 3

1.4 OPERATION ........................................................... 1 4

1.5 WARRANTY AND PARTS ORDERING ................................... 1 5

1 1

SECTION I

THE TTU500FA TRANSMITTER

1.1 INTRODUCTION:

The EMCEE TTU500FA LPTV Transmitter is a remarkably compact design rated to provide

500 watts peak visual and 25 watts average aural power on any FCC specified channel extending

from 470 to 806MHz. The TTU500FA is completely solid-state supplying maximum performance

and reliability through the liberal utilization of Laterally Diffused Metal Oxide Semiconductors

(LDMOS). Comprised of a modulator, an EMEX1 2 Watt UHF Exciter, one 500 Watt UHF Amplifier

drawer, an Output Section for filtering and power measurement, and panels for power distribution

and metering/control, the TTU500FA is easy to service and maintain with RF alignment practically

nonexistent. A number of controls and indicators, furnished on the transmitter’s Control/Metering

panel and the EMEX1 Exciter front panel, provide convenient operation while displaying the results

of the transmitter's diagnostic circuitry.

The TTU500FA is designed for the express purpose of broadcasting as authorized by the U.S.

Federal Communications Commission under Part 74, Subpart G, of the FCC Rules and Regulations.

1.2 SPECIFICATIONS:

Visual:

Output Power 500 watts peak

Emission 5M75C3F visual

Color Transmission NTSC, PAL, or SECAM

Output Frequency 470-806MHz

(FCC - Ch.14-69)

(CCIR - Ch.21-62)

Frequency Stability Visual Carrier ±500Hz

Output Power Stability ±0.5dB

Spurious Products 60dB below peak sync

Harmonics 60dB below peak sync

In-band Intermodulation (IM3)52dB below peak sync

Differential Gain ±5%

Differential Phase ±3

1 2

Low Frequency Linearity 5%

Frequency Response ±0.5dB

Sideband Response Better than FCC 73.687(a)(1)

Envelope Delay Better than FCC 73.687(a)(3)

Output Impedance/Connector 50 ohms / 7/8" EIA flange

Video Signal to Noise 55dB

Video Input Level 1 volt peak-to-peak nominal

Video Input Impedance 75 ohms unbalanced

Aural:

Output Power 25 watts average

Emissions 250KF3E

Frequency Stability ±200Hz re. visual

Audio Input Level 0dBm nominal

Audio Input Impedance 600 ohms balanced

Audio Distortion <1%

FM Noise < 55dB

General/Mechanical:

Ambient Temperature 30 C to +50 C

Power Requirements 230Vac ± 15%, 1 phase, 50/60Hz, 4kW

Power Consumption: 2kW w/black picture

Power Factor 0.9

Mechanical Dimensions 48"H x 22"W x 31"D

Weight 300 lb.

1 3

1.3 INSTALLATION:

Except where otherwise noted, the connectors mentioned in the following instructions are located

on the rear of the transmitter.

1. After unpacking the transmitter, a thorough inspection should be conducted to reveal any

damage which may have occurred during shipment. If damage is found, immediately notify

the shipping agency and advise EMCEE Broadcast Products Customer Service or its field

representative. Also check to see that any connectors, cables or miscellaneous equipment,

which may have been ordered separately, are included.

2. Place the transmitter in a clean, weatherproof environment providing adequate ventilation

for the exhaust fans at the rear of the transmitter drawers. It is important to maintain the

transmitter's ambient temperature within the 30 C and +50 C limits. Cooler ambient

temperatures will provide increased reliability.

3. Place the transmitter in its permanent location near a single-phase receptacle that supplies

230Vac at 50/60Hz. The ac source should have a minimum power capacity of 4kW.

IMPORTANT

Do not apply ac power to the transmitter at this time since its RF output must be

properly loaded before being placed in operation.

4. Set all circuit breakers, including the customer's incoming ac line breaker, to the OFF

position. Ac breakers can be found on the transmitter’s AC Distribution Panel, at the rear of

the amplifier and Exciter drawers, and on the front AC Power panel. Place an appropriate

power line protector (surge suppressor) across the ac line that supplies the transmitter.

5. Connect the baseband video and audio cables (customer supplied) to the transmitter's VIDEO

and AUDIO connectors located on the upper panel at the rear of the transmitter cabinet.

6. Connect the transmitting antenna cable (or a 1kW, 50 ohm dummy load) to the 7/8" EIA

flange connector marked RF OUTPUT located through the center rear of the cabinet’s top

cover.

7. Verify that the power cords of the Modulator (110V/15A), Exciter (110/15A) and 500W Power

Amplifier drawer (220V/20A) are plugged into the receptacles at the bottom of the transmitter

cabinet. Also check to see that any ancillary equipment included in the cabinet (i.e. Video

Detect Switch, Stereo Generator, etc.) are connected to the appropriate ac sockets.

8. Check to see that all RF cables and wire harnesses are properly connected and secure.

9. Using the 4-prong, twist-lock, female plug supplied with the transmitter, fabricate an ac power

cord (Figure 1 1) and plug it into the transmitter's AC MAINS connector at the bottom rear

of the transmitter cabinet. Open the incoming ac mains wall breaker and connect the other

end of the power cord into an appropriate 220Vac electrical outlet.

1 4

1.4 OPERATION:

Assuming the installation instructions of Section 1.3 have been completed and the transmitter is

receiving baseband video and audio signals, proceed with the following steps to place the transmitter

in operation. Except where otherwise noted, the controls, switches, and indicators mentioned in

these steps are located on the front of the transmitter.

1. Open the AC POWER circuit breaker located on the bottom front panel of the transmitter and

close the incoming ac mains breaker. Insure that the EMEX1 Exciter OPERATE/STANDBY

switch is in the off/out (STNDBY) position and the AGC/MANUAL button is in the off/out

(MANUAL) position. Place the transmitter’s Control/Metering panel FWD/REFL meter switch

to the FWD/out position.

2. Place the three AC Distribution Panel breakers (CB2, CB3, CB4), located at the lower rear

of the cabinet, to the on position. Also switch the Exciter and amplifier drawer rear panel

breakers to on.

3. Move the AC POWER circuit breaker located on the bottom front panel of the transmitter to

the ON position.

4. If applicable, place the Modulator's power switch to ON and verify that it is providing 87.5%

video modulation. If necessary, adjust the Modulator for the proper video depth of

modulation as described in its instruction manual. Also check to see that the audio peaks are

not overmodulating the aural carrier.

5. Verify the following transmitter responses:

a. The fans at the rear of each drawer should be operating.

b. The Exciter’s green LED indicators should react as follows:

SYNTHESIZER LOCK – on

IF STATUS – on

AMPLIFIER STATUS – on

LINEARITY CORRECTOR – on

AGC ACTIVE – off

SWEEP MODE – off

OPERATE/STANDBY – off

VSWR RESET – off

AGC voltmeter – 1 segment lit at approximate center

RF POWER meter – 0%

c. The green LED indicators on the transmitter’s Control/Metering panel should respond

as follows:

AMPLIFIER TEMP – off

AMPLIFIER – on

POWER SUPPLY – off

RF POWER meter – 0%

FWD – on

REFL – off

1 5

6. Turn the Exciter's OUTPUT LEVEL ADJUST two or three turns counterclockwise and press

the OPERATE/STANDBY switch in to place the transmitter in OPERATE. Then verify the

following responses of the transmitter:

a. The Exciter’s OPERATE/STANDBY switch indicator is now lit green.

b. The POWER SUPPLY Control/Metering panel indicator is now lit green.

c. The status of all other indicators previously mentioned is the same.

7. Check to see that the Control/Metering panel’s meter switch is in the FWD/out position and

then slowly turn the Exciter’s OUTPUT LEVEL ADJUST clockwise until a 100% indication

appears on the Control/Metering panel’s RF POWER meter. The Exciter’s RF POWER

meter should also be displaying a 100% indication.

8. After 10 minutes of operation press the Exciter’s AGC/MANUAL switch in to engage the

transmitter’s output automatic gain control. If necessary and with a small tuning tool, slowly

turn the AGC LEVEL ADJUST to bring the transmitter’s RF POWER meter reading back to

100%.

9. Place the Control/Metering panel's meter switch to REFLD and verify that the RF POWER

meter indicates no more than 10% returned power. If the reflected power is more than 10%,

shut down the transmitter and check the VSWR of the transmitting antenna and its associated

cable.

10. Place the Control/Metering panel's meter switch to FWD for constant monitoring of the

transmitter's final output power.

The transmitter is now in operation. Check its coverage area for clean, sharp television reception.

If the reception or picture quality is unsatisfactory, examine the amount of power delivered to the

transmitting antenna (see Section 3.5) and, if necessary, examine the antenna orientation and

antenna transmission line VSWR to insure maximum radiation in the proper direction.

1.5 WARRANTY AND PARTS ORDERING:

Warranty – EMCEE warrants its equipment to be free from defects in material and workmanship for

a period of one year after delivery to the customer. Equipment or components returned as defective

(prepaid) will be, at our option, repaired or replaced at no charge as long as the equipment or

component part in question has not been improperly used or damaged by external causes

(e.g., water, ac line transients or lightning). Semiconductors are excepted from this warranty and

shall be warranted for a period of not more than ninety (90) days from date of shipment. Equipment

or component parts sold or used by EMCEE, but manufactured by others, shall carry the same

warranty as extended to EMCEE by the original manufacturer.

Equipment Returns – If the customer desires to return a unit, drawer, or module to EMCEE for

repair, follow the procedure described below:

1. Contact EMCEE Customer Service Department by phone or fax for a Return Authorization

Number.

1 6

2. Provide Customer Service with the following information:

Equipment model and serial numbers.

Date of purchase.

Unit input and output frequencies.

Part number (PN) and Schematic Diagram designator if a module is being sent.

Detailed information concerning the nature of the malfunction.

The customer shall designate the mode of shipping desired (e.g., Air Freight, UPS, Fed Ex, etc.).

EMCEE will not be responsible for damage to the material while in transit. Therefore, it is of utmost

importance that the customer insure the returned item is properly packed.

Parts Ordering – If the customer desires to purchase parts or modules, utilize the following

procedure:

1. Contact EMCEE Customer Service by phone or fax indicating the customer's purchase order

number. If the purchase order number is provided by phone, written confirmation of the order

is required.

2. Also provide:

The equipment model and serial number.

The unit input and output frequencies.

The quantity, description, vendor, number, and designation of the parts needed as found in

the Parts Lists subsection of this manual.

If a module is required, give the part number (PN) and Schematic Diagram designator

(e.g., 30404029).

Designate the mode of shipping desired (e.g., Air Freight, UPS, Fed Ex, etc.).

Shipping and billing addresses.

Spare and Replacement Parts – The Spare Modules and Components section of this manual

provides a detailed listing of the modules and some discrete components contained within the

transmitter. The listing contains those modules or components considered to be essential

bench-stock items and should be available to the technician at all times. The Schematic or

Interconnection Diagram is the governing document of this manual. Should there be a discrepancy

between a modules or components list and a diagram, the diagram takes precedence. Such a

discrepancy is possible since manufacturing changes cannot always be incorporated immediately

into the instruction manual.

Component Referencing – A transmitter may consist of a modulator or receiver, a number of

modules and components mounted in drawers, and components or modules mounted to panels or

directly to the cabinet. Components mounted in a module which is included in a drawer take the

drawer number and the module number in addition to a component number. Thus the reference

designator A2A1Q1 means transistor Q1 in module A1 of drawer A2. Components mounted in a

drawer take only the drawer number and a component number (e.g., A2M1 designates meter M1 of

drawer A2). Components mounted directly to a panel take only the panel number and a component

number. Components and modules mounted directly to the cabinet take only a component or

module number.

1 7

For EMERGENCY technical assistance, EMCEE offers a toll free, 24-hour, 7-day-a-week

customer service hot line: 1-800-233-6193.

SECTION II

CIRCUIT DESCRIPTION

2.1 MODULATOR ......................................................... 2 1

2.1a Video Detector Switch ............................................... 2 1

2.2 EMEX1 2 WATT UHF EXCITER ......................................... 2 1

2.2a Linearity Corrector .................................................. 2 2

2.2b IF/Converter ....................................................... 2 3

2.2c UHF Synthesizer ................................................... 2 6

2.2d Reference Oscillator ................................................. 2 7

2.2e UHF Bandpass Filter ................................................ 2 7

2.2f 2 Watt UHF Amplifier ................................................ 2 7

2.2g Metering Coupler ................................................... 2 9

2.2h Metering Detector................................................... 2 9

2.2i Control/Interface Board .............................................. 2 9

2.2j Display/Monitor Board .............................................. 2 20

2.2k 28V/15V/5V Power Supply ........................................... 2 24

2.3 500 WATT UHF POWER AMPLIFIER DRAWER ......................... 2 24

2.3a Power Splitter..................................................... 2 25

2.3b 300W UHF Power Amplifier .......................................... 2 25

2.3c Power Combiner................................................... 2 27

2.3d Amplifier Status Interface ............................................ 2 27

2.3e Power Supply/Thermal Interface ....................................... 2 27

2.3f 32V Power Supply ................................................. 2 28

2.4 OUTPUT SECTION ................................................... 2 29

2.4a UHF Bandpass Filter ............................................... 2 29

2.4b Directional Coupler ................................................. 2 29

2.4c Metering Detector.................................................. 2 29

2.5 CONTROL/METERING PANEL ......................................... 2 30

2.5a Control/Monitor Board .............................................. 2 30

2 1

SECTION II

CIRCUIT DESCRIPTION

2.1 MODULATOR:

EMCEE EM1 / Scientific Atlanta 6340 / RF Comm. 2000 A1

IF OUT 8dBm peak visual typical

The modulator processes baseband video and audio signals to provide a composite IF output

composed of a visual carrier at 45.75MHz with 5M75C3F modulation, and an aural carrier at

41.25MHz with 250KF3E modulation. Any of these modulators can be used to drive the EMEX1

2 Watt Exciter drawer (A2). The optional video sense circuit provides an indication of whether the

modulator is receiving a baseband video signal. The output of the video sense is either a logic

high ( +5Vdc) with video present or a logic low ( 0Vdc) when video is not present. This logic

signal is used by the Exciter Control/Interface Board (A2PC1) to place the transmitter in standby

if the video signal is lost.

2.1a Video Detector Switch:

Burst VDS A9

For those modulators which do not contain a video sense alarm, the Burst Electronics Video

Detector Switch (Model VDS) will be installed in the transmitter cabinet. The VDS detects the

presence of composite video connected to its A INPUT directly from the VIDEO connector mounted

on the Video/Audio/Remote Panel (A8J2). If a loss of video is detected, then the unit switches to

the B INPUT, lights its red LED and energizes an internal TALLY relay. Through this relay, a

ground is sent to the Exciter Control/Interface circuit via the transmitter’s Control/Monitor board

(A5PC1) placing the transmitter in a nonradiating condition.

2.2 EMEX1 2 WATT UHF EXCITER:

Interconnection Diagram 40404001/Rev 55 A2

Composite IF IN (J1) 8dBm peak visual

21dBm average aural

RF OUT (J2 & J3) +18dBm typical peak visual

+5dBm typical average aural

The EMEX1 Exciter drawer converts the composite IF signal from the modulator to the desired

UHF frequency while amplifying this RF signal to the appropriate output level. The Exciter supplies

approximately 200mW of peak visual power to drive the 500W UHF Power Amplifier drawer (A3).

Power control, automatic gain control (AGC) and heterodyne conversion are performed by the

IF/Converter module (PC1). Utilizing the composite IF signal, the Linearity Corrector furnishes

performance improvements for the transmitter’s ICPM, differential phase and gain, sync amplitude

2 2

and intermodulation. The UHF Synthesizer supplies a programmable LO to the IF/Converter mixer

where the LO and IF signals are combined to create the desired UHF frequency. The UHF signal

from the Converter module is then passed through the UHF Bandpass Filter (FL1) to remove the

unwanted LO and sum products from the conversion process while passing and amplifying the

desired difference signals. The signal is then amplified approximately 25dB by the 2 Watt UHF

amplifier (A1) and passed through the Metering Coupler (CP1). Here, a forward RF sample is

provided for use by the Metering Detector (A3) while the main signal is passed to the output of the

drawer.

Metering and control functions are provided by the Metering Detector, the Display/Monitor board

(PC3) and the Control/Interface Board (PC4). The Display/Monitor Board has several status and

diagnostic LED indicators which are presented on the Exciter’s front panel. The Control/Interface

board provides for various controls and logic circuits for proper operation of the transmitter. Dc

power for the Exciter is supplied by a small, efficient multioutput switching power supply PS1 which

furnishes ±28, ±15 and ±5 volts.

2.2a Linearity Corrector:

Schematic Diagram 40404011/Rev 55 A2PC2

IF IN (J1) 11dBm typical

IF OUT (J2) 12dBm typical

Gain with S1 ENABLE/DISABLE (J1-J2) 0 to 2dB typical

Current Draw 610mA @ +15Vdc

The Linearity Corrector is a six-stage, unity gain circuit which compensates for nonlinear distortions

generated in the transmitter's Class AB 500 Watt Power Amplifier drawer. When properly adjusted,

it provides correction to the transmitter’s output signal for sync amplitude, differential gain,

differential phase, ICPM and intermodulation. Corrector amplifiers U1 through U8 are all

monolithic amplifier stages providing approximately 12dB of gain per device. A phase correction

network is centered around amplifiers U2 through U5 while the circuitry surrounding U7 and U8

corrects for differential gain and sync compression. When properly adjusted, the phase and gain

correction networks will collectively reduce intermodulation distortion.

Input amplifier U1 is biased through resistor R1 and inductor L1 which acts as an RF choke.

Capacitor C2 is utilized as a B+ bypass with coupling capacitors C1 and C3 advancing the input

signal to the matching T-attenuator made up of resistors R2, R3 and R4. At hybrid splitter DC1,

the IF carrier is divided into two equal amplitude signals which are 90 out of phase. At the

splitter’s 90 port, a negative phase-shift network composed of inductor L3 and capacitors C15

through C18 adds another 22.5 shift to the signal ( 112.5 total) before amplification by U3.

Conversely, connected to the 0 port of the splitter is a positive phase-shift network comprised of

inductor L2 and capacitors C4 throughC7. Here the 0 signal is shifted in the positive direction by

22.5 resulting in a 135 total difference between the two signals. In order to keep the amplitude

of each signal similar, the circuits surrounding amplifiers U2 through U5 are essentially identical

with the same biasing, bypassing and coupling described for U1. Transformers T3 and T4 on the

negative shift side of the circuit are 2:1 step-up types identical to T1 and T2, but necessary to

efficiently drive gain expansion diodes CR1 and CR2. Through adjustment of slope potentiometers

R15 and R25 and threshold (cut-in) pots R21 and R30, the amplitude of the negative shifted signal

can be varied to add to or subtract from the positive shifted signal at in-phase combiner CP1.

When adjusted properly, this circuit can then correct the differential phase, intermodulation and

ICPM distortions created by the transmitter’s power amplifier. At the output of combiner CP1 the

2 3

IF signal passes through a matching pi-attenuator comprised of resistors R35, R36 and R37 before

amplification by U6, U7 and U8. Transformers T5 and T6 again double the signal voltage to

properly drive the gain expansion diodes CR3 and CR4 which compensate for differential gain and

sync compression created in the 500 Watt Power Amplifier (A3).

The variable gain expansion networks, which provide linearity correction, are centered around dual

diodes CR1 through CR4, slope potentiometers R15, R25, R41, R57, unity gain dc amplifiers U9,

U10, U11, threshold potentiometers R21, R30, R47, R55 and ENABLE/BYPASS switch S1. The

threshold (cut-in) potentiometers determine the point on the IF waveform where the correction, or

gain expansion, will occur and the slope potentiometers dictate the amount of correction/expansion

to be used at that breakpoint. With S1 in the ENABLE position, the four diode pairs form nonlinear

circuits where each diode is reverse biased and the amount of reverse bias dictates the point at

which the diode turns on during the positive and negative cycles of the visual IF carrier envelope.

Each diode is biased using voltages established by the threshold potentiometers in conjunction with

dc amplifiers U9, U10, U11 and U12. L4 through L6 and L9 through L12 isolate the IF signal from

the diode threshold biasing circuitry. When the positive and negative peaks of the visual signal

envelope are sufficient to forward bias a diode pair, the pair turns on placing the resistance of its

respective slope potentiometer in parallel with the series arm of its L-pad (R14, R24, R40, R50).

As a result, the attenuation of the visual IF carrier is reduced during this period causing the

waveform to stretch. Slope control R41 is typically used to correct differential gain while R57

primarily adjusts sync amplitude.

With S1 in the BYPASS position, ground is applied to FET switches Q1 and Q2 placing each diode

pair in hard reverse bias preventing conduction throughout the positive and negative cycles of the

IF carrier envelope. Due to the high reverse resistance provided, each diode network essentially

represents a resistive L-pad (R14/R16, R24/R31, R40/R42, R50/R58) with the IF signal attenuated

by a fixed amount in each location. As a result, no linearity correction is provided.

2.2b IF/Converter:

Schematic Diagram 40404021/Rev 53 A2PC1

IF INPUT (J1) 0dBm to 30dBm peak visual

CORRECTOR LOOP Out (J3) 11dBm peak visual typical

CORRECTOR LOOP In (J4) 12dBm peak visual typical

RF OUT 10 to 18dBm

LO INPUT (J5) +13dBm minimum

Current Draw 42mA @ +15V

31mA @ 15V

185mA @ +5V

The IF/Converter performs three tasks in this transmitter. With the first AGC loop it furnishes level

control for the incoming signal from the modulator, upconverts the IF signal to the desired UHF

channel and then controls the transmitter’s output power through a second gain control loop.

The modulator’s IF input, provided at J1, is amplified or attenuated by variable gain amplifier U1.

This integrated circuit, controlled by the output of integrator U4 via switch S1, (U1) can produce

wide variations in gain ranging from +30dB to 10dB. At the output of U1 is coupling capacitor C3

and 2:1 step-down transformer T1 required for proper impedance matching between U1 and in-

phase splitter CP1. At the output of CP1, two equal amplitude IF signals are delivered for differing

applications. The signal at pin CP1-3 is used to provide a reference for the input AGC loop, while

2 4

the second signal at pin CP1-4 is fed to the Linearity Corrector (PC2) connected to output J3. Both

signals pass through attenuators (3dB and 7dB respectively) which are connected to identical

monolithic amplifiers, U7 and U8. These devices, offering approximately 14dB of signal gain, are

furnished bias through resistors R15/R22 and RF chokes L1/L2. The output of amplifier U8 is

connected, through coupling capacitor C19, to a variable PIN attenuator composed of diodes CR7

and CR8. This diode array forms a pi-attenuator operated by buffer U9 whose input (pin 5) is

supplied control voltage from the Exciter’s front panel OUTPUT LEVEL ADJUST. With maximum

voltage from U9 (+15V) the attenuator will exhibit minimum attenuation of approximately 2dB.

With minimum voltage the attenuator can provide more than 50dB of loss to the signal. This

attenuator is utilized as the main power control and standby mechanism for the transmitter.

At the output pin 3 of U7 is the second IF signal required by the input AGC circuit as a power

reference representing the incoming modulator signal level. This signal is passed through coupling

capacitor C16 to integrated circuit U6, an RMS detector. At pin 7, U6 outputs the video component

of the IF visual carrier while C11 rolls off the aural energy contained in the signal. The amplitude

of the video is then doubled using op-amp U5A and then sent to peak detector CR3 via pins 1 and

2 of jumper JP1. (Pins 2 and 3 of JP1 are utilized for average digital power detection only.)

Capacitor C9 and resistor R10 filter the peak video component from diode CR3 and this dc voltage

is sent to unity gain buffer U5B. The dc level at the output of U5B (pin 7), which is now

proportional to the peak power of the visual signal entering the IF/Converter, will be approximately

+3V when the modulator level into the Converter board is at the midpoint of its input AGC window

(15dBm peak). This potential then appears at pin 6 of integrator U4B where it is compared to the

voltage on pin 5 ( +3V) generated by divider R7/R8. When the values of each voltage at pins 5

and 6 are equal, the output of U4B at pin 7 will be zero, holding variable gain amplifier U1 at the

center of its gain extremes (+10dB) via pins 8 and 1 of electronic switch S1. (The gain of U1 can

also be set to its center by applying a low to the INPUT AGC CONTROL line which is connected

to pin 6 (IN) of switch S1. This low, supplied by the OPERATE/SWEEP switch PC4S1 on the

Control/Interface board, will disconnect the input AGC voltage at S1-8 from S1-1 and connect the

ground at S1-2, 3 to S1-1 effectively placing a zero voltage on pin 1 of U1.) If the input level from

the modulator at J1 increases, the outputs of U7, U6, U5A and U5B will also increase forcing pin 7

of U4B negative and proportionally reducing the gain of U1. Conversely, if the input from the

modulator were to be reduced, the output of U4B would swing positive causing U1 to increase its

gain compensating for the signal reduction. Under normal transmitter operating conditions, the

signal provided at the CORRECTOR LOOP output (J3) will be approximately 11dBm peak visual.

However, if the IF signal is significantly reduced ( 25dBm) or removed completely, the potential

at the output of U4B will exceed +2.5V causing the level at input pin 2 of U4A to exceed the

reference (2.5V) provided at pin 3 through divider R5/R6. This action would drive output pin 1 of

U4A to zero, turning off the IF STATUS light (PC3DS5) on the Exciter’s front panel and placing a

low on the LEVEL ADJUST line attached to pin 5 of U9 increasing the attenuation of the associated

PIN diode circuit to maximum ( 50dB).

After proceeding through the Linearity Corrector, the IF signal is fed to CORRECTOR LOOP input

J4 at an approximate level of 12dBm. Here the signal is furnished a 50 ohm match using

pi-attenuator R30/R31/R32. Hybrid amplifier U1, biased through resistor R33 and RF choke L3,

provides 14dB of gain and delivers the signal to in-phase 2-way splitter CP2 via coupling capacitor

C29. At output pins 3 and 4 of CP2 are two equal amplitude IF signals used, respectively, to drive

the output AGC loop (U13 through U18) and to be mixed to the wanted UHF channel after passing

through the output control attenuator. Made up of PIN diodes CR9/CR10 and controlled by U18,

this attenuator is capable of 2dB to 50dB of attenuation and ultimately sets the output power of the

transmitter. From the output control attenuator the IF signal is transferred to mixer MX1 through

coupling capacitor C51 and pins 1 and 2 of jumper JP3. (Connecting pins 2 and 3 of JP3 brings

the IF signal to test point TP1.) In MX1 the IF is then upconverted to the desired UHF signal as

a result of combining with the local oscillator frequency presented at LO INPUT J5. At the output

of the mixer (pin 4) resistors R67/R68/R69 provide 5dB of attenuation and the appropriate

2 5

impedance match for amplifier U20 via capacitor C52. U20 supplies 13dB of amplification for the

UHF frequencies with resistor R70 and choke L5 furnishing the necessary power to the hybrid.

From output pin 2 of U20, the amplified signal is brought to the OUTput connector J5 where it will

be fed to the subsequent UHF Bandpass Filter (A2FL1) and eventually to the transmitter’s output.

The second IF signal, present at pin 3 of splitter CP2, functions as the signal level reference for

the output AGC loop. Matching attenuator R34/R35/R36 provides the proper impedance for the

signal brought to pin 1 of 14dB hybrid amplifier U13. Bias is supplied to U13 through resistor R37

and choke L4 with capacitor C31 acting as an RF bypass. Capacitors C32 and C33 in conjunction

with resistor R38 provide coupling and matching from the output of amplifier U13 to the input of

RMS detector U14. As with detector U6 of the input AGC loop, U14 separates the video program

from the IF visual carrier while attenuating the aural components through C35. The demodulated

video signal, found at pin 7 of U14, is amplified by U15A and passed through detector CR4 via

jumper JP2 pins 1 and 2. (Pins 2 and 3 of JP2 are utilized for average digital power detection

only.) The resulting peak of the video signal is transformed into an average dc voltage using filter

CR36/R42 which is then buffered with unity gain amplifier U15B. At the output of divider R43/R45,

the positive detected voltage created by the IF signal at CORRECTOR LOOP J4 meets the

negative POWER REFERENCE voltage supplied to connector J6-8 from the transmitter’s output

power Metering Detector (A7A1) through inverting amplifier U16B. When their associated circuits

are correctly adjusted, these two voltages will be opposite but equal in value, theoretically yielding

0 volts at the output of adder circuit U16A, operational amplifier U17A and integrator U17B. With

the front panel AGC/MANUAL switch PC3S2 depressed (in), this voltage is then sent through pins

8 and 1 of switch S2 and divider R56/R61 to amplifier U18A which controls the attenuation value

of PIN diodes CR9/CR10 and, subsequently, the output power of the transmitter. (With 0V at the

output of switch S1, PIN attenuator CR9/CR10 provides approximately 3dB of signal reduction.

With +15V from S1, the PIN attenuator will furnish almost no resistance and with 15V, diodes

CR9/CR10 will supply about 6dB of signal loss.) If, for some reason the transmitter’s output power

were to drop, the positive voltage at J6-8 would be reduced, making the output of U16B less

negative. The more positive voltage at pin 3 of U16 will force its output positive while the outputs

of U17A and U17B go negative and positive, respectively. The change in level, sent to U18 via

switch S2, forces pin 1 of U18A high reducing the attenuation provided by PIN diodes CR9/CR10.

This reduction in attenuation will be proportional to the power decrease seen at the transmitter’s

output, thereby bringing the transmitter’s power back to its appropriate operating level. In the case

where the transmitter’s output increases above its rated power, the exact opposite happens. The

POWER REFERENCE voltage at J6-8 will increase taking the U16A input negative. The output

from U17A will go positive forcing U17B to send a negative voltage to U18 via switch S2. The

negative voltage from U18A will cause PIN diode attenuator CR9/CR10 to increase resistance,

decreasing the transmitter’s signal level to its proper value.

To defeat the output AGC, the front panel AGC/MANUAL switch must be released (out), placing

a ground on the OUTPUT AGC CONTROL line at pin 10 of J6. This low, applied to pin 6 of switch

S2, causes the incoming AGC voltage at pin 8 of S2 to be removed from pin 1 and connected to

the ground at pins 2, 3. The 0V potential sent to U18A will fix PIN diodes CR9/10 at 3dB, the

center of their attenuation range. Amplifier U18B, which also follows the output of S2 at its input

pin 5, acts as a unity gain buffer forwarding the output AGC voltage to the Exciter’s front panel

AGC meter (A2PC3DS12) and to the RJ45 REMOTE plug (A8J1) on the VIDEO/AUDIO/REMOTE

rear panel.

2 6

2.2c UHF Synthesizer:

Schematic Diagram 30367094/Rev B A2A2A1

LO OUT (J2) +15dBm minimum

Frequency Stability 0.3ppm / 30 C to +70 C

10MHz REF. IN (J1) 3.5V P/P square wave

SYNTH LOCK (Pin J4-A) logic high - unlocked / logic low - locked

Current Draw 15mA @ +28V

120mA @ +15V

36mA @ +5V

The UHF Synthesizer is a phase-lock loop circuit that uses 10MHz as a reference to develop a

manually programmable CW signal for the Mixer in the IF/Converter module (A2PC1MX1). The

frequency of the synthesizer output signal (or LO) is calculated as the sum of the visual IF carrier

from the modulator and the visual carrier of the transmitter’s UHF output channel. The LO

frequency is programmed by the setting of switches S1 through S4 which are accessible via access

holes on the Synthesizer’s module (A2A1) cover. The switch settings for each UHF channel and

the resulting LO frequencies are provided in Table 3 1 of Section 3.9.

A 10MHz signal from Reference Oscillator A2A2 is brought to the Synthesizer module through

connector J1 (10MHz IN). At the connector, the two sections of divider chip U4 perform a binary

divide-by-5 count creating a 400kHz signal at the OSCin pin 27 of synthesizer chip U1. At the

same time, the output of voltage controlled G1 (RF OUT), amplified by U5 and available as the

transmitter’s LO at J2 (OUT), is also amplified by U6 and fed to a ÷64/÷65 prescaler, U2. The U2

prescaling factor is ultimately selected by programming switches S1 through S4 which set the MOD

CONTROL line at pin 9 of U1 to either high or low. When a high is seen at pin 6 (MC) of prescaler

U2, the chip will divide the VCO output by 64. With a low at U2-6 the prescaler will divide the VCO

output by 65. After prescaling, the signal is sent to pin 1 of U1 (Fin) from U2-4 (OUT) and, with the

aid of the A and N counters within U1, the prescaled signal is also divided down to 50kHz using a

divide-by-ratio selected through the switch settings of S1 through S4. This 50kHz, derived from

voltage controlled oscillator G1, is sent to a phase detector for comparison with the 50kHz taken

from the high stability 10MHz reference. At the U1 phase detector outputs 0/V and 0/R (pins 7 & 8),

loop filter U3 integrates the incoming correction pulses and sends them to VCO G1 as a dc control

voltage after suppression filter C14/C15/C24/R5/R13. If the frequency generated by VCO G1 is

lower than the frequency selected by programming switches S1-S4, a pulse train will appear at

pin 5 of U3 forcing the control voltage at pin 7 higher, thereby raising the frequency of the

oscillator. If the VCO output is higher than the frequency selected by the programming switches,

then pulses will appear at U3 pin 6 pushing the control voltage lower at U3-7 to reduce the

frequency from G1. The corrected frequency is then passed through matching attenuator R7/8/9

and amplified by U5 for delivery to the IF/Converter mixer. (For NTSC System M operation, A0

and A1, pins 21 and 23 on U1, are grounded. For PAL System B/G and D/K operation, A0 and A1

are made high by opening the traces at pins 21 and 23 thereby adding the characteristic 150kHz

to the LO.

When the synthesizer is locked to its programmed frequency, pin LD of chip U1 provides a high

which saturates Darlington pair Q1 after capacitor C28 changes through resistor R16. This time

delay is created to ensure that the synthesizer has successfully locked before supplying a low to

the SYNTH LOCK line. During an unlocked condition, the LD pin switches low discharging C28

through diode CR1 and reverse biasing Q1. A high (+5V) is now present on the SYNTH LOCK line

indicating an unlocked condition.

2 7

2.2d Reference Oscillator:

Schematic Diagram 10368037/Rev B A2A2A2

10MHz REF. OUT (J1, J2) 3.5V P/P square wave

Frequency Stability 0.3ppm / 30 C to +60 C

Current Draw 15mA @ +5V

The Reference Oscillator provides a high stability 10MHz signal which provides accuracy and long-

term frequency stability for the UHF Synthesizer (A2A2A1). This reference module is centered

around a 10MHz temperature-compensated crystal oscillator (G1) using 5V as power. The output

from G1 is buffered by two exclusive-OR gates used as inverters. The output signal from each

gate is a 10MHz low-level square wave with a frequency stability of 0.3 parts per million (ppm).

2.2e UHF Bandpass Filter:

Schematic Diagram 20404015/Rev 51 A2FL1

INPUT (J1) 10 to 18dBm

OUTPUT (J2) 0 to 8dBm

Bandwidth (J1-J2) 8MHz to 15MHz @ 1dB

Gain (J1-J2) 10dB

Current Draw 50mA @ +5V

The UHF Bandpass Filter is a six-section comb-line design joined with a single-stage amplifier to

provide 10dB of total module gain. The first three sections of the filter, composed of variable

capacitors C1/C2/C3 and their associated tuned stubs, are terminated at the input of U1, a 14dB

amplifier. Variable capacitors C1/C2/C3 and C4/C5/C6 electrically lengthen or shorten their

connected stubs to pass the chosen UHF channel with the appropriate coupling provided by

spacing between the stubs. For extra stub length at lower frequencies, capacitors C7/C8/C9/C10/

C11/C12 are added to operate at channels below 560MHz. The bias for U1 is obtained from the

5 volt power supply via R1 and RF choke FB1 (ferrite bead) with bypassing furnished by capacitors

C15/C16/C17. Loading wires W1/W2/W3/W4 set the input and output impedance of each three-

section filter segment, dictating the overall bandwidth and loss of the circuits. FL1 is tuned to

select the desired UHF mixer products from the lower sideband, or difference signal, found at the

RF OUTPUT of the IF/Converter (A2PC1).

2.2f 2W UHF Amplifier:

Schematic Diagram 30404029/Rev 54 A2A1

INPUT (J1) 0 to 8dBm peak visual

OUTPUT (J2) +22dBm peak visual

Gain (J1-J2) 20dB to 38dB manual set

Frequency Response (J1-2) ±1dB/470-806MHz

Current Draw 500mA @ +28V

210mA @ +15V

2 8

The 2W UHF Amplifier is a variable gain, class A module that provides amplification to the

selected UHF channel. The amplifier is a three-stage, class A, microstrip design capable of 38dB

gain and 2 watts peak visual output. The first stage is centered around broadband monolithic

amplifier U1 rated for 10dB of gain. U1 is provided bias from 9 volt regulator U2 through filter FB1

and parallel resistors R1/R2. Input and output signal coupling is supplied by capacitors C1/C2 with

B+ bypass furnished by C3 through C6 and C16/C17. At the output of amplifier U1 is 90 hybrid

coupler HY1 configured as a variable gain control using PIN diodes CR1/CR2 and the GAIN

ADJUST voltage applied to E3. As the E3 GAIN ADJUST voltage is increased (using the

AMPLIFIER GAIN ADJUST A2PC4R7 on the Control/Interface board), PIN diodes CR1/CR2 begin

to conduct, creating a low impedance at the 0 and 90 ports of the hybrid. Due to mismatch

generated at these two ports, the resulting reflected power is added in phase at the hybrid’s ISO

port affording lower attenuation for the through signal. Conversely, as the GAIN ADJUST voltage

decreases, the PIN diodes conduct less generating a higher impedance at the 0 and 90 ports

making 47 ohm resistors R5/R6 electrically more apparent as power absorbing loads. With less

power reflected back into the hybrid, less power will appear at the ISO port making for increased

attenuation of the through signal. Variable gain adjust HY1 is capable of 3dB to 18dB of

attenuation.

From HY1 the UHF signal is coupled into field-effect transistor Q1 via capacitor C9 and an input

matching circuit made up of capacitor C10 and a tuned microstrip network. Biased from 9V

regulator U2 through resistors R11/R12, Q1 furnishes 12dB of signal amplification and with a drain

current of approximately 140mA. Capacitors C12/C13/C14/C15 supply RF bypassing for the bias

voltage with C11/C18 acting as signal coupling capacitors positioned at the input and output of 3dB

matching attenuator R13/R14/R15. At the input of 8 pin DIP power FET Q2 is a microstrip network

with matching capacitors C19/C20/C24 and variable capacitor C35. Connected directly to the

28 volt supply, Q2 is powered through a current regulator circuit centered on transistor Q5 and

drain resistors R20 through R23. This circuit continuously maintains the drain voltage and current

of Q2 over a wide variation of load and temperature. The required collector voltage and current

of this device is established by potentiometer R19, which controls the conduction of regulator Q5,

ultimately setting the 500mA drain current of Q2. At the output the amplified signal proceeds

through another matching network made up of capacitors C31/C32 and various microstrip tuning

elements. Coupling capacitor C33 passes the signal from Q2 to output connector J2.

Within the 2W UHF Amplifier module, fault circuits monitor the status of RF devices U1, Q1 and

Q2. Centered on transistors Q3/Q4/Q5, these fault circuits detect the presence of an open RF

device within the module and send a signal to the Exciter’s front panel AMPLIFIER STATUS

indicator. Under normal operation, transistors Q3/Q4/Q5 are forward biased generating approx-

imately 8.5 volts at collector resistors R4/R9/R26 pushing diodes CR3/CR4/CR5 into reverse bias.

With CR3/CR4/CR5 not conducting, the voltage at pin 5 of comparator U3 will be approximately

7.5 volts as dictated by resistive divider R27/R28. When compared to the 5.7 volt level provided

by divider R28/R30 at pin 6, the higher voltage at pin 5 will force U3 high, lighting the AMPLIFIER

STATUS LED (A2PC3DS1) to indicate the amplifier is operating properly. Due to the low created

on its collector resistor (R4/R9/R26), one of the back biased diodes would begin to conduct taking

U3-5 lower than the reference voltage at pin 6. This action would immediately create a low at the

output of U3 (pin 7) extinguishing the front panel AMPLIFIER STATUS light indicating the amplifier

module should be repaired or replaced.

2 9

2.2g Metering Coupler:

Schematic Diagram N/A A2CP1

Insertion Loss (J1-J2) <0.5dB

Forward Coupling (J1-J3) 30dB ± 1dB

The Metering Coupler is a three-port device designed to provide a forward RF sample to the

Metering Detector (A2A3) with minimal loss to the Exciter’s output signal. The RF signal is applied

to the coupler's input port (J1) and exits the coupler with a maximum of 0.5dB of loss at J2. A

10dB sample of the forward power is provided at J3 and connected to the FWD PWR SAMPLE

port of the Metering Detector. A dc signal, proportional to the Exciter’s output power, is then sent

to the front panel RF POWER meter via the Control/Interface (A2PC4) and Display/Monitor

(A2PC3) circuits.

2.2h Metering Detector:

Schematic Diagram 30400038/Rev 53 A2A3

The Metering Detector contains two identical circuits for monitoring forward and reflected output

power while providing dc voltages proportional to those signal levels. However, in the case of the

EMEX1 Exciter, only the forward power detection circuit is utilized. A sample of the output signal

from the Metering Coupler (A2CP1) is supplied to the Visual port FWD PWR Sample input (J1) of

the detector. This signal is passed through resistive attenuator R1/R2/R3 and coupling capacitor

C1 to integrated circuit U1, an RMS detector. At pin 7, U1 outputs the video component of the

UHF visual carrier while C3 rolls off the aural energy contained in the signal. The amplitude of the

video is then doubled using op-amp U2 and sent to peak detector CR1 via pins 1 and 2 of jumper

JP1. (Pins 2 and 3 of JP1 are utilized for average digital power detection only.) Capacitor C4 and

resistor R7 filter the peak video component from diode CR1 and this dc voltage is sent to unity gain

buffer U2. The dc level at the output of U2 (pin 7), which is now proportional to the peak power of

the visual signal entering the Metering Detector, will be approximately +3V. This voltage will be

delivered to the Display/Monitor RF POWER meter (A2PC3DS9) after processing on the Control/

Interface board (A2PC4).

2.2i Control/Interface Board:

Schematic Diagram 40404036/Rev 53 A2PC4

Current Draw 12mA @ +15V

4mA @ 15V

112mA @ +5V

The Control/Interface board, positioned in the right rear corner of the drawer, is the control center

for the EMEX1 Exciter. All local and remote monitoring signals, control voltages, interlock circuits,

external AGC loops and power supply voltages are routed to their proper destination through this

circuit board. Each multipin connector on the Control/Interface is dedicated to an individual module

or PC board as described below.

210

IF/Converter Module Interface (PC1J6)

Jack – Pin # Function

J8 – 1 GND: Ground to PC1J8-1

J8 – 2 15V: From J3-3 to PC1J8-2

J8 – 3 +15V: From J3-5 to PC1J8-3

J8 – 4 +5V: From J3-4 to PC1J8-4

J8 – 5 INPUT AGC CONTROL: With S1 in OPERATE, U3C sends a high to PC1S1

permitting the input AGC voltage to control variable gain amplifier PC1U1. With

S1 in the sweep position U3C provides a low to PC1S1 fixing the gain of PC1U1

at 10dB. A low is also sent to U4C which provides a low to set the attenuation

of output PIN diodes PC1CR9/CR10. To eliminate output power surges from the

Exciter when S1 is switched from SWEEP to OPERATE, one-shot multivibrator

U10B sends a temporary low to U3D causing U2A and U8A to go low. The low

is forwarded via J10-21, PC3J1-21, LEVEL ADJUST PC3R16, PC3J1-23,

J10-23, J8-7, and PC1-7 causing PC1U9 to set IF input attenuator PC1CR7/CR8

to maximum attenuation. After 1 second, ramp-up circuit CR1, R26, R27, C17

slowly discharges bringing the Exciter/transmitter output back to normal.

J8 – 6 IF STATUS: With the presence of an IF signal at the input of PC1, a high is

provided from PC1U4A to U4B, lighting IF STATUS LED PC3DS5 via R19,

J10-24, PC3J1-24, and PC3Q5. If the IF input is removed, PC1U4 will then

provide a low to U4B extinguishing the IF STATUS LED PC3DS5 while forcing

U3D and U2A low. The resulting low from U8A will force IF input attenuator

PC1CR7/CR8 to maximum attenuation until the IF signal is returned (see

description under J8-5).

J8 – 7 LEVEL ADJUST: The Level Adjust voltage controls the output power of the

Exciter (and, therefore, the transmitter) by controlling the attenuation provided

to the IF input signal by attenuator PC1CR7/CR8 through buffer PC1U9. This

voltage originates from U8A and is varied by front panel LEVEL ADJUST

PC3R16 via J10-21, PC3-21, PC3-23, J10-23 and J8-7.

J8 – 8 POWER REFERENCE: This voltage is provided to PC1J6-8 as the reference

for the output AGC loop controlling attenuators PC1CR9/CR10 which act as the

Exciter/transmitter output power adjust. The voltage originates in either the

Exciter Metering Detector A3 via J9-5, buffer U5A and jumper JP1-1 & 2 or from

a detector external to the Exciter. In the TTU500FA, the FWD PWR voltage is

generated in the transmitter’s Output Section detector A7A1J3-5, enters at J5-7

to buffer U7A and jumper J1-2 & 3. In both instances the PWR REF voltage is

sent to AGC ADJUST PC3R15 via J10-19, PC3J1-19, PC3J1-17, J10-17 to J8-8.

J8 – 9 OUTPUT AGC VOLTS: From PC1J6-9, this ±15V signal is transformed to a 0

to +15V level and sent to J5-4 and J10-25. The voltage at J10-25 is used to

drive the front panel AGC meter PC3DS12 via PC3J1-25. The voltages at J5-4

are for remote monitoring at the Exciter’s rear panel. In the TTU500FA, these

voltages are passed to the Control/Meter Panel Monitor/Control Board A5PC1J5

and looped to connector A5PC1J4. From here they are sent to open REMOTE

connector A8J1 on the transmitter’s rear Video/Audio/Remote Panel.

IF/Converter Module Interface (PC1J6)

Jack – Pin # Function

211

J8 – 10 OUTPUT AGC CONTROL: This voltage is applied to switch PC1S2 which

determines if the IF output AGC is active (high) or fixed (low). With the

OPERATE/SWEEP switch S1 in the SWEEP position, the ground at U3C will

cause the output U4C-8 to go low, switching PC1S2 to place a ground on

PC1U18. This low forces PIN diodes PC1CR9/CR10 to stabilize at the center of

their attenuation range ( 3dB). Releasing the front panel AGC/MANUAL switch

PC3S2 will deactivate the output AGC by supplying a ground to J10-9 via

PC3J1-9. The low at U4A-2 will cause the outputs of U4D and U4C to go low,

again inhibiting the AGC. In the TTU500FA, a power supply or transistor failure

occurring in the 500W Power Amplifier drawer (A3) will furnish a low at J4-1 from

A5PC1J3-1. The low at U4A-1 will drive the outputs of U4D and U4C toward

ground with the same affect. If the operator wishes to remotely deactivate the

transmitter’s output AGC, a ground can be applied to pin 7 of REMOTE jack

A8J1 on the Video/Audio/Remote Panel at the rear of the transmitter cabinet.

This ground will be fed to U4D-12 from A5PC1J5-6 to J5-6 and to U4D, pushing

U4C-8 low. Whether the output of AND gate U4C is at a logic high or low, that

signal is also sent to pin 18 of J10 through resistor R23 and on to front panel

AGC ACTIVE LED P3DS6. If the voltage is high, transistor PC3Q6 will be

forward biased causing the LED to turn on, indicating the output AGC is active.

If the voltage at PC3J1-18 is low, PC3Q6 will not conduct and PC3DS6 will not

illuminate indicating an inactive output AGC.

2W UHF Amplifier Module Interface (A1J3)

Jack – Pin # Function

J6 – 1 +28V: From J3-6 to A1J3-1

J6 – 2 +15V: From J3-5 to A1J3-2

J6 – 3 STATUS: This high or low voltage originates from A1J3 pin 3 to indicate the

status of the transistors within the 2W UHF Amplifier module. A high indicates

that the devices are operating properly creating highs from U3A and U3B while

lighting AMPLIFIER STATUS LED PC3DS1 via R8, J10-26 and PC3J1-26. If a

transistor fails within A1, the STATUS line will go low sending the outputs U3A-3,

U3B-6 and U2B-6 low. A low will emanate from U8A and pass through J10-21,

PC3J1-21, LEVEL ADJUST PC3R16, PC3J1-23, J10-23, J8-7, PC1J6-7 and

PC1U9-5, increasing the IF attenuation of PIN diodes PC1CR7/CR8 and signif-

icantly reducing the output power of the Exciter and, therefore, the transmitter.

The low at the output of U3A will also extinguish the front panel AMPLIFIER

STATUS LED PC3DS1 via J26 and PC3J1-26.

J6 – 4 GAIN ADJUST VOLTAGE: This 0 to 12V potential is delivered to A1J3-4 to

control the gain of the 2W Amplifier module through manipulation of hybrid

attenuator A1HY1/CR-1/CR2. The voltage is delivered by variable voltage regu-

lator U12 with AMPLIFIER GAIN ADJUST potentiometer R7 controlling its out-

put. The voltage to R7 is supplied by 5V regulator U11 fed from the 15V

supply.

J6 – 9 GND: Ground to A1J3-9

212

UHF Synthesizer Module Interface (A2A1J3/J4, A2A2J2)

Jack – Pin # Function

J2 – 1 GND: Ground to A2A1J3-D

J2 – 2 GND: Ground to A2A2J2-B

J2 – 3 +5V: From J3-4 to A2A1J3-C

J2 – 4 +5V: From J3-4 to A2A2J2-A

J2 – 5 +15V: From J3-5 to A2A1J3-A

J2 – 6 +28V: From J3-6 to A2A1J3-B

J2 – 8 LOCK STATUS: This voltage is brought in from A2A1J3-A as an operational

indicator for the Synthesizer. A low (synthesizer locked) at the base of Q1 will

forward bias this transistor, placing a high at the inputs of AND gate U1A-1 & 2

forcing its output pin 3 high. Assuming the outputs of AND gates U1B and

U2A/B/C/D are high, the LEVEL ADJUST OUT voltage at J10-21 will be kept

high with the Exciter’s (and transmitter’s) output power unaffected. A high, indi-

cating an unlocked synthesizer, will back bias transistor Q1 forcing lows from

AND gates U1A/B, U2A/B/C/D and amplifier U8A. The low is forwarded via

J10-21, PC3J1-21, LEVEL ADJUST PC3R16, PC3J1-23, J10-23, J8-7, and

PC1-7 causing buffer PC1U9 to set IF input attenuator PC1CR7/CR8 to maxi-

mum attenuation. This action reduces the output power of the Exciter approxi-

mately 50dB to insure that no off frequency signals are transmitted.

UHF Bandpass Filter Module Interface (FL1J3)

Jack – Pin # Function

J1 – A +5V: From J3-4 to FL1J3-A

J1 – B GND: Ground to FL1J3-B

Linearity Corrector Module Interface (PC2J3)

Jack – Pin # Function

J7 – 1 GND: Ground to PC2J3-1

J7 – 3 LINEARITY CORRECTOR ACTIVE: With switch PC2S1 in the ENABLE posi-

tion, +15V is divided down to +5V and presented to input pins 9 and 10 of U1C

via PC2R64, PC2J3-3, J7-3 and R36. The high at U1C-8 is then forwarded to

J10-16, PC3J1-16, PC3Q3 used to turn on front panel LINEARITY

CORRECTOR light PC3DS3.

J7 – 4 +15V: From J3-5 to PC2J3-4

213

Power Supply Module Interface (PS1TB2)

Jack – Pin # Function

J3 – 1 GND: Ground from TB1-4

J3 – 2 GND: Ground from TB1-4

J3 – 3 15V: From PS1TB2-1 and distributed to circuits and interface jacks on PC4

J3 – 4 +5V: From PS1TB2-9 and distributed to circuits and interface jacks on PC4

J3 – 5 +15V: From PS1TB2-4 and distributed to circuits and interface jacks on PC4

J3 – 6 +28V: From PS1TB2-6 and distributed to interface jacks on PC4

Metering Detector Module Interface (A3J3)

Jack – Pin # Function

J9 – 1 REFL PWR: Metering voltage proportional to the reflected power found at the

output of the Exciter is provided from A3J3-1, buffered by U5B and amplified by

U6B according to the setting of REFL PWR METER ADJ potentiometer R33.

This voltage is sent to J10-14 but is not utilized in this application. When the

Exciter is not driving higher power amplifiers, pins 1 and 2 of jumper JP2 are

closed sending the metering voltage to pin 6 of U6A, the VSWR overload refer-

ence amplifier. When the Exciter is driving higher power amplifiers, JP2 pins

2 & 3 are connected, bringing reflected metering voltage in at J5-3 from the

detector (A7A1) monitoring the output of the transmitter. With high reflected

output power, the voltage at U6A-3 will exceed the reference at pin 2, a level

determined by VSWR OVLD REF potentiometer R12 which is typically set for

25% reflected power. Output pin U6A-1 will turn positive causing output pins

5 & 6 of flip-flop U9A to change states. As U9A-5 goes negative, gate U2D will

output a low on pin 11 sending U2A-3 and U8A-1 low. The low at J10-21

proceeds to PC3J1-21, LEVEL ADJUST PC3R16, PC3J1-23, J10-23, 8-7 and

PC1-7, causing buffer PC1U9 to set IF input attenuator PC1CR7/CR8 at maxi-

mum attenuation. This action reduces the output power of the Exciter and trans-

mitter approximately 50dB to insure that no amplifier damage occurs due to

excessive output VSWR. Concurrently, the high generated at U9A-6 is used to

light VSWR OVERLOAD indicator PC3DS8 via J10-11, PC3J1-11 and transistor

PC3Q8.

J9 – 3 +5V: To A3J3-3 from J3-4

J9 – 4 GND: Ground to A3J3-4

J9 – 5 FWD PWR: Voltage proportional to the forward output power of the Exciter is

provided from A3J3-5 to buffer U5A and amplifier U7B whose gain is controlled

by FWD PWR METER ADJ potentiometer R42. R42 is adjusted so that U7B

provides enough voltage to register a 100% reading on the front panel RF

POWER meter PC3DS9/10/11 when the Exciter is providing its rated output

power. This voltage is supplied to the meter through J10-15, PC3J1-15, squaring

circuit PC3U2 and amplifier PC3U1.

214

Remote Control/Monitor Interface (A5PC1J5)

Jack – Pin # Function

J5 – 1 REMOTE/OP/STBY: In the TTU500FA, this pin is connected to the Video/Audio/

Remote panel plug A8J1-5 via A5PC1J4-5 and A5PC1J5-1. Normally this input

is left open allowing the high to remain at pin 13 of U1D. If the operator wishes

to place the Exciter and/or transmitter in standby from a remote location, a

ground is applied to J5-1 forcing the output pin 11of U1D to go low, causing

succeeding AND gates U1B through U2A to send a low to the input of U8A-3.

The low is forwarded via J10-21, PC3J1-21, LEVEL ADJUST PC3R16,

PC3J1-23, J10-23, J8-7, and PC1-7 causing buffer PC1U9 to set IF input attenu-

ator PC1CR7/CR8 to maximum attenuation. The Exciter (or transmitter) is now

in standby and prevented from radiating a signal.

J5 – 3 REFL PWR IN: This voltage is proportional to the reflected power found at the

output of the transmitter that the Exciter might be driving. When driving higher

power amplifiers, JP2 pins 2 & 3 are connected, bringing reflected metering

voltage in from the detector (A7A1) monitoring the output of the transmitter. The

voltage travels from A7A1P3-1 to A5PC1J6-1 where it is buffered by A5PC1U4A

and sent to PC1J5-7 and the Exciter REMOTE plug J5. With high reflected

output power, the voltage at U6A-3 will exceed the reference at pin 2, a level

determined by VSWR OVLD REF potentiometer R12, which is typically set for

a reflected power 25% of the transmitter’s forward rating. Output pin U6A-1 will

turn positive causing output pins 5 & 6 of flip-flop U9A to change polarity. As

U9A-5 goes negative, gate U2D will output a low on pin 11 sending U2A-3 and

U8A-1 low. The low at J10-2 proceeds to PC3J1-21, LEVEL ADJUST PC3R16,

PC3J1-23, J10-23, J8-7 and PC1-7, causing buffer PC1U9 to set IF input attenu-

ator PC1CR7/CR8 at maximum attenuation. This action reduces the output

power of the Exciter and transmitter approximately 50dB to insure that no

amplifier damage occurs due to excessive output VSWR. Concurrently, the high

generated at U9A-6 is used to light VSWR OVERLOAD indicator PC3DS8 via

J10-11, PC3J1-11 and transistor PC3Q8.

J5 – 4 AGC VOLT: This AGC voltage, originating from IF/Converter buffer PC1U18B

and pin 9 of PC1J6, is amplified by U8B before proceeding to J5-4. In the

TTU500FA, the voltage is provided for monitoring at A8J1-2 of the Video/Audio/

Remote rear panel REMOTE plug via A5PC1J4-2 and A5PC1J5-4.

J5 – 5 REMOTE VSWR RESET: A momentary ground is normally applied to this pin

to bring the unit out of standby due to a VSWR overload caused by excessive

returned power at the output of the Exciter (J9-1) or transmitter (J5-3). In the

TTU500FA transmitter, this ground can be applied to pin 6 of J1 on the Video/

Audio/Remote panel (A8) at the transmitter’s rear. The ground will proceed to

A5PC1J4-6, A5PC1J5-5 and then to J5-5. (A momentary ground is also pro-

vided by Exciter front panel VSWR RESET switch PC3S3.) The transition from

high to low on pin 4 of flip-flop U9A will reset pins 5 & 6 to their original Q (high)

and Q NOT (low) states, removing the low from U2D-13 and the high from

VSWR OVERLOAD LED control transistor PC3Q8, respectively. Front panel

LED PC3DS8 will then turn off and IF input attenuator PC1CR7/CR8 will be

returned to normal operating levels.

Remote Control/Monitor Interface (A5PC1J5)

Jack – Pin # Function

215

J5 – 6 REMOTE AGC ON/OFF: By applying a ground, this pin can be used to deacti-

vate the output AGC voltage that controls IF/Converter PIN diode attenuator

PC1CR9/CR10. In the TTU500FA, the same result is achieved by placing a

ground on pin 7 of jack A8J1 on the rear Video/Audio/Remote panel. This low

will be passed on to A5PC1J4-7, looped through A5PC1J5-6 and sent to J5-6.

The low now found at U4D-12 will force U4D-8 and J8-10 low forcing PIN diodes

PC1CR9/CR10 to stabilize at the center of their attenuation range ( 3dB).

Whether the output of AND gate U4C is at a logic high or low, that signal is also

sent to pin 18 of J10 through resistor R23 and on to front panel AGC ACTIVE

LED P3DS6. If the voltage is high, transistor PC3Q6 will be forward biased

causing the LED to turn on, indicating the output AGC is active. If the voltage

at PC3J1-18 is low, PC3Q6 will not conduct and PC3DS6 will not illuminate

indicating an inactive output AGC.

J5 – 7 FWD PWR IN: The incoming voltage at this pin is proportional to the forward

output power of the transmitter and is forwarded to pin 3 of buffer U7A from

Metering Detector A7A1J3-5 via A5PC1J6-5, buffer amplifier A5PC1U4A and

A5PC1J5-7. When this voltage is available, the Exciter is driving higher power

equipment and pins 1 & 3 of jumper JP1 are closed sending the metering voltage

from U7A to the front panel AGC ADJUST amplifier PC3U1 through J10-19 and

PC3J1-19. From AGC ADJUST PC3R15, this PWR REFERENCE signal

reaches PC1J6-8 of the IF/Converter by PC3J1-17, J10-17 and J8-8. This

voltage acts as the reference for the IF/Converter’s output AGC loop by

controlling variable attenuator PC1CR9/CR10 and compensating for any power

variations occurring at the transmitter’s output. If for some reason the transmit-

ter’s output power were to drop, the positive voltage at J8-8 would be reduced.

The change in level reduces the attenuation provided by PIN diodes PC1CR9/

CR10 in proportion to the power decrease seen at the transmitter’s output,

thereby bringing the transmitter’s power back to its appropriate operating level.

In the case where the transmitter’s output increases above its rated output, the

PWR REFERENCE voltage at J8-8 will increase causing attenuator PC1CR9/

CR10 to increase resistance, decreasing the transmitter’s output signal level to

its proper value.

J5 – 8 GND: Ground provided to the operator’s remote equipment from the Exciter or

to the TTU500FA Video/Audio/Remote rear panel jack A8J1-8 via A5PC1J4-8

and A5PC1J5-8.

Transmitter Control/Monitor Interface (A5PC1J3)

Jack – Pin # Function

J4 – 1 AMP STATUS IN: In the TTU500FA, a power supply failure, overtemperature

condition or transistor failure occurring in the 500W UHF Power Amplifier drawer

(A3) will furnish a low to this pin from A5PC1J3-1. The resulting lows at U4A-3,

U4D-11 and U4C-8 are sent through J8-10 to IF/Converter switch PC1S2 which

determines if the IF output AGC is active (high) or fixed (low). With a low at

PC1S2-6, pins 1 & 2, 3 are closed placing a ground on PC1U18-3. This low

forces PIN diodes PC1CR9/CR10 to stabilize at the center of their attenuation

Transmitter Control/Monitor Interface (A5PC1J3)

Jack – Pin # Function

216

range ( 3dB). At the same time, the low output of AND gate U4C is passed to

pin J10-18 through resistor R23 and on to front panel AGC ACTIVE LED control

transistor PC3Q6. Since the voltage at PC3J1-18 is low, PC3Q6 will not conduct

and PC3DS6 will turn off indicating an inactive output AGC. If the voltage was

high, transistor PC3Q6 would forward bias causing the LED to turn on, indicating

the output AGC was active.

J4 – 3 AMP BIAS CONTROL: This voltage is generated by AND gate U2C and

forwarded to switching FETs A5PC1Q1/Q2 which activate or deactivate the

power supplies (A3PS1/PS2) contained within the 500W UHF Power Amplifier

drawer A3. Power Supply activation requires that UHF Synthesizer A2 be locked

(J2-8 high) producing a high at U1A-3, that the OPERATE/STANDBY lines be

open (J5-1 and J10-7 high) creating a high at U1D-11 and that the VIDEO

SENSE line (J4-5) provides a high to U2C-10. Under these conditions the high

furnished at U2C-8 will activate amplifier drawer A3. If any of the above

conditions change creating a logic low at J2-8, J5-1, J10-7 (OPERATE/

STANDBY switch PC3S1) or J4-5, then the 500W UHF Power Amplifier drawer

will be shut down.

J4 – 5 VIDEO SENSE: A high/low indication for the presence or absence of video pro-

gramming is delivered to this input from the Video Detector Switch (VDS) TALLY

jack. With video present at INPUT A9-A, an open is sent from A9J1-NO to J4-5

via A5PC1J8-1 and A5PC1J3-5 placing a high on U2C-10. If a loss of video

occurs, a ground appears at A9J1-NO forcing U2C low at pins 10 & 6 which

deactivates power supplies A3PS1/PS2 in the 500W UHF Power Amplifier

drawer.

J4 – 8 GND: Ground to A5PC1J3-8

Display/Monitor Interface (PC3J1)

Jack – Pin # Function

J10 – 1 +5V: From J3-4 to PC3J1-1

J10 – 2 GND: Ground to PC3J1-2

J10 – 3 15V: From J3-3 to PC3J1-3

J10 – 5 +15V: From J3-5 to PC3J1-5

J10 – 7 OPERATE/STANDBY: An open or ground is brought in on this pin from the front

panel OPERATE/STANDBY switch PC3S1 via PC3J1-7 to place the Exciter/

transmitter in operate (switch in) or standby (switch out) while illuminating or

extinguishing OPERATE indicator PC3DS7. If the incoming logic level is high

and assuming all other gates are high, pin U1D-11 will remain at 5V keeping the

AMP BIAS CONTROL (J4-3) level high to activate the 500W UHF Power

Amplifier drawer. Simultaneously, the output of U8A and voltage at J10-21

remain normal through LEVEL ADJUST PC3R16, PC3J1-23, J10-23, J8-7, and

PC1-7 causing buffer PC1U9 to set IF input attenuator PC1CR7/CR8 at its

appropriate value. If OPERATE/STANDBY switch PC3S1 supplies a ground to

Display/Monitor Interface (PC3J1)

Jack – Pin # Function

217

J10-7, gate U1D will go low at pin 11 forcing logic lows at the outputs of U1B

through U2A. The resulting low at J4-3 will shut down power supplies A3PS1/

PS2 causing the 500W UHF Power Amplifier to become inactive. Op-Amp U8A

will also go negative supplying a low at J10-21, PC3J1-21, LEVEL ADJUST

PC3R16, PC3J1-23, J10-23, J8-7 and PC1-7, causing buffer PC1U9 to set IF

input attenuator PC1CR7/CR8 to maximum attenuation. The Exciter and

transmitter are now in standby and prevented from radiating a signal.

J10 – 9 AGC/MANUAL: An open or ground will appear here depending on the position

of the front panel AGC/MANUAL switch PC3S2 which determines if the

IF/Converter (PC1) output AGC is active (in/high) or fixed (out/low). Releasing

the front panel AGC/MANUAL switch will supply a ground to U4A-2 causing the

outputs of U4D and U4C to go low, switching PC1S2 to place a ground on

PC1U18. This low forces PIN diodes PC1CR9/CR10 to stabilize at the center of

their attenuation range ( 3dB) thereby inhibiting the AGC while extinguishing the

front panel AGC ACTIVE LED PC3DS6 via J10-18, PC3J1-18 and PC3Q6. With

the AGC/MANUAL switch pressed in, a high will appear at J10-9 and, assuming

all other inputs to U4C, U4D and U4A are high, the high at J8-10 will release

switch PC1S2, remove the ground from PC1U18 and release diodes PC1CR9/

CR10 to respond to the normal output AGC voltages while AGC ACTIVE lamp

PC3DS6 turns on.

J10 – 11 VSWR LED: If high reflected power at the output of the Exciter or transmitter

initiates a VSWR overload, pin 6 of flip-flop U9A will shift high causing VSWR

OVERLOAD LED PC3DS8 to illuminate via J10-11, PC3J1-11 and PC3Q8.

Under normal operation U9A-6 and the associated VSWR LED line will be low

keeping VSWR OVERLOAD LED PC3DS8 off.

J10 – 13 VSWR RESET: This input is connected to the front panel VSWR RESET

momentary switch PC3S3. In the event of a VSWR overload, pressing this

switch provides a ground to reset pin 4 of flip-flop U9A which changes the states

of pins 5 & 6 to their normal Q/high and Q NOT/low outputs. As a consequence,

the high activating LED PC3DS8 is removed turning off the front panel VSWR

OVERLOAD indicator and the low at U2D-13 switches high sending U2A-3 and

U8A-1 in the same direction after ramp-up circuit R26/R27/CR1/C17 charges.

The high at J10-21 proceeds to PC3J1-21, LEVEL ADJUST PC3R16, PC3J1-23,

J10-23, J8-7 and PC1-7 causing buffer PC1U9 to release IF input attenuator

PC1CR7/CR8 to normal attenuation. This action brings the Exciter and trans-

mitter out of standby by slowly increasing the unit’s output power to normal.

J10 – 14 REFLECTED POWER: No connection

J10 – 15 FORWARD POWER: From Metering Detector A3J3-5 via J9-5, a voltage pro-

portional to the forward output power of the Exciter is provided to buffer U5A and

amplifier U7B whose gain is controlled by FWD PWR METER ADJ potentiome-

ter R42. R42 is adjusted for U7B to provide enough voltage for a 100% reading

on the front panel RF POWER meter PC3DS9/10/11 when the Exciter is pro-

viding its proper output power. This voltage is supplied to the meter through

J10-15, PC3J1-15, squaring circuit PC3U2 and amplifier PC3U1.

Display/Monitor Interface (PC3J1)

Jack – Pin # Function

218

J10 – 16 LINEARITY CORRECTOR ACTIVE LED: With Linearity Corrector switch

PC2S1 in the ENABLE position, the corrector circuits active with +15V divided

down to +5V and presented to input pins 9 & 10 of U1C via PC2R64, PC2J3-3,

J7-3 and R36. The resulting high at U1C-8 is forwarded to J10-16, PC3J1-16

and PC3Q3 used to turn on front panel LINEARITY CORRECTOR light PC3DS3.

J10 – 17 PWR REFERENCE IN: This voltage, proportional to the monitored output

power, originates from either the Exciter (A3J3-5) or transmitter (A7A1J3-5)

Metering Detector and is buffered by U5A or U7A, respectively. The voltage

connected to JP1 is forwarded to the front panel AGC ADJUST PC3R15 through

J10-19, PC3J1-19, amplifier PC3U1, PC3J1-17 to J10-17. This PWR

REFERENCE signal reaches PC1J6-8 of the IF/Converter through J8-8 and acts

as the reference for the IF/Converter’s output AGC loop by controlling variable

attenuator PC1CR9/CR10 and compensating for any power variations occurring

at the Exciter’s/transmitter’s output. If for some reason the Exciter’s/transmitter’s

output power were to drop, the positive voltage at J8-8 would be reduced. The

change in level reduces the attenuation provided by PIN diodes PC1CR9/CR10

in proportion to the power decrease, thereby bringing the output power back to

its appropriate operating level. In the case where the Exciter’s/transmitter’s

output increases above its rated output, the PWR REFERENCE voltage at J8-8

will increase causing attenuator PC1CR9/CR10 to increase resistance,

decreasing the output signal level to its proper value.

J10 – 18 AGC MANUAL LED: This output line connected to U4C-8 via R23 controls front

panel AGC ACTIVE LED PC3DS6 through PC3J1-18 and switching transistor

PC3Q6. The AGC ACTIVE indicator will be lit when concurrent highs are pro-

vided from the OPERATE/SWEEP switch S1 (OPERATE position), from the

AMP STATUS IN line at J4-1, from the front panel AGC/MANUAL switch PC3S2

(AGC position) input at J10-9 and from the REMOTE AGC ON/OFF line at J5-6

forcing the output of U4C high.

J10 – 19 PWR REFERENCE OUT: This voltage, proportional to the monitored output

power, originates from either the Exciter (A3J3-5) or transmitter (A7A1J3-5)

Metering Detector and is buffered by U5A or U7A, respectively. The voltage

connected to JP1-2 is forwarded to the front panel AGC ADJUST PC3R15

through J10-19, PC3J1-19, amplifier PC3U1, PC3J1-17 to J10-17. The signal

reaches PC1J6-8 of the IF/Converter through J8-8 and acts as the reference for

the IF/Converter’s output AGC loop by controlling variable attenuator PC1CR9/

CR10 and compensating for any power variations occurring at the Exciter’s/

transmitter’s output. If for some reason the Exciter’s/transmitter’s output power

were to drop, the positive voltage at J8-8 would be reduced. The change in level

reduces the attenuation provided by PIN diodes PC1CR9/CR10 in proportion to

the power decrease seen at the Exciter’s/transmitter’s output, thereby bringing

the power back to its appropriate operating level. In the case where the trans-

mitter’s output increases above its rated power, the PWR REFERENCE voltage

at J8-8 will increase causing attenuator PC1CR9/CR10 to increase resistance,

decreasing the Exciter’s/transmitter’s output signal level to its proper value.

Display/Monitor Interface (PC3J1)

Jack – Pin # Function

219

J10 – 20 SWEEP LED: This output controls the operation of the front panel SWEEP

MODE LED PC3DS4. With the OPERATE/SWEEP switch in the SWEEP (low)

position, U3C supplies a low to R23, J10-20, PC3J1-20 and transistor PC3Q4

which is forward biased to turn on PC3DS4. Placing switch S1 in the OPERATE

position will generate a high causing the SWEEP MODE indicator to go out.

J10 – 21 LEVEL ADJ OUT: Assuming the outputs of AND gates U1A/U1B/U1D/U2C/U2B/

U2D/U2A are high, amplifier U8A provides a reference of approximately 14V at

this output which is fed to the front panel LEVEL ADJUST potentiometer

PC3R16. This pot facilitates manual adjustment of IF/Converter variable attenu-

ator PC1CR7/CR8 and, therefore, manual control of the Exciter’s/transmitter’s

output power. If one of the above mentioned AND gates shifts low due to a fault

signal or command from:

J8-6 IF STATUS

S1 OPERATE/SWEEP

J6-3 2W AMPL STATUS

J2-8 LOCK STATUS

J9-1 REFL PWR

J5-1 REMOTE OP/STBY

J4-5 VIDEO SENSE

J10-7 OPERATE/STANDBY

then a low will emanate from U8A and pass through J10-21, PC3J1-21, LEVEL

ADJUST PC3R16, PC3J1-23, J10-23, J8-7, PC1J6-7 and PC1U9-5, increasing

the IF attenuation of PIN diodes PC1CR7/CR8 and significantly reducing the

output power of the Exciter/transmitter effectively placing the unit in standby.

J10 – 22 SYNTH LOCK LED: This output controls the activation and deactivation of the

front panel SYNTHESIZER LOCK light PC3DS2. The voltage originates at

A2A1J3-A as an operational indicator for the Synthesizer. A low (synthesizer

locked) from J2-8 to the base of Q1 will forward bias this transistor, placing a

high at the inputs of AND gate U1A-1 & 2 forcing its output pin 3 high. This high

is passed through R5, J10-22, PC3J1-22 forward biasing PC3Q2 causing

PC3DS2 to light. If Synthesizer A2A1 unlocks, a high will be sent to J2-8 which

ultimately shuts off the SYNTHESIZER LOCK indicator PC3DS2.

J10 – 23 LEVEL ADJ IN: This voltage is developed in amplifier U8A and sent through

LEVEL ADJUST PC3R16 and passed from this input (J10-23) to J8-7 as a

control level for variable attenuator PC1CR7/CR8 in the IF/Converter (see

J10-21 above).

J10 – 24 IF STATUS IN: This signal is taken from the output of U4B via resistor R19 for

control of IF STATUS LED PC3DS5. With the presence of an IF signal at the

input of PC1, a high is provided from PC1U4A to U4B, lighting IF STATUS LED

PC3DS5 via R19, J10-24, PC3J1-24, and PC3Q5. If the IF input is removed,

PC1U14 will then provide a low to U4B extinguishing the IF STATUS LED

PC3DS5 while forcing U3D and U2A low.

Display/Monitor Interface (PC3J1)

Jack – Pin # Function

220

J10 – 25 OUTPUT AGC VOLT: This voltage is used to drive the front panel AGC meter

PC3DS12. From PC1J6-9 a ±15V signal is transformed to a 0 to +15V level by

U8B and sent to J5-4 and J10-25. The voltage at J10-25 is used to drive the

front panel AGC meter via PC3J1-25 and LED bar graph driver PC3U3.

J10 – 26 AMPLIFIER STATUS LED: This high or low voltage originates from A1J3-3 to

indicate the status of the transistors within the 2W UHF Amplifier module. A high

at J6-3 and U3A-3 indicates that the devices are operating properly while lighting

AMPLIFIER STATUS LED PC3DS1 via R8, J10-26, PC3J1-26 and PC3Q1. A

low at the output of U3A indicating a device failure within the amplifier will

extinguish the front panel AMPLIFIER STATUS LED PC3DS1 via the same path.

2.2j Display/Monitor Board:

Schematic Diagram 30404041/Rev 52 A2PC3

Current Draw 33mA @ +15V

7mA @ 15V

300mA typ./360mA max. @ +5V

The Display/Monitor board is positioned behind the front panel of the drawer and contains the

indicator lights, adjustments and switches necessary to operate and maintain the EMEX1 Exciter.

Control/Interface Board Interface (PC4J10)

Jack – Pin # Function

J1 – 1 +5V: From PC4J10-1

J1 – 2 GND: From PC4J10-2

J1 – 3 15V: From PC4J10-3

J1 – 5 +15V: From PC4J10-5

J1 – 7 OPERATE/STANDBY: An open or ground is provided at this pin to PC4J10-7

from OPERATE/STANDBY switch S1 placing the Exciter/transmitter in an active

(switch in ) or inactive (switch out) mode. With S1 in, transistor Q7 will conduct

causing OPERATE LED DS7 to illuminate while sending a high to AND gate

PC4U1D. If its associated gates PC4U1B through PC4U2A are also high, 500W

Power Amplifier A3 will activate via PC4J4-3 (AMP BIAS CONTROL) due to the

high from PC4U2C-8. Simultaneously, the voltage at PC3J10-21 will remain

normal through LEVEL ADJUST R16, holding IF input attenuator PC1CR7/CR8

at its previously set value for proper Exciter/transmitter output power. With S1

released, a ground at PC4U1D-12 will force logic lows at the outputs of the

succeeding AND gates resulting with a low at PC3J4-3 making the 500W UHF

Power Amplifier inactive. The negative at PC3J10-21 through LEVEL ADJUST

Control/Interface Board Interface (PC4J10)

Jack – Pin # Function

221

R16 causes IF input attenuator PC1CR7/CR8 to provide maximum attenuation.

The Exciter and transmitter are now in standby with OPERATE LED DS7

extinguished.

J1 – 9 AGC/MANUAL: An open or ground will appear here depending on the position

of the front panel AGC/MANUAL switch S2 which determines the IF/Converter

(PC1) output AGC is active (switch in) or fixed (switch out). Releasing the front

panel AGC/MANUAL switch will supply a ground to PC4U4A-2 causing the

outputs of PC4U4D/U4C to go low. This low forces IF PIN diodes PC1CR9/

CR10 to stabilize at the center of their attenuation range ( 3dB) thereby

inhibiting the output AGC while extinguishing front panel AGC ACTIVE LED DS6

via PC4J10-18, J1-18 and Q6. With the AGC/MANUAL switch pressed in, a high

will appear at PC4J10-9 and, assuming all other inputs to U4C, U4D and U4A

are high, the high at PC4J8-10 will release switch PC1S2, remove the ground

from PC1U18 and release diodes PC1CR9/CR10 to respond to the normal output

AGC voltages while AGC ACTIVE lamp DS6 turns on.

J1 – 11 VSWR LED: Illumination and deactivation of VSWR OVERLOAD LED DS9 is

controlled by the voltage at the base of transistor Q8 delivered from flip-flop

PC4U9A-6 via PC4J10-11. Under normal operation PC4U9A-6 is low keeping

Q8 back biased and DS8 off. With a VSWR overload, PC4U9A-6 changes state

for causing Q8 to conduct and DS8 to light.

J1 – 13 VSWR RESET: S3 is a momentary switch which sends a ground to reset pin 4

of VSWR overload flip-flop PC4U9A changing the states of pins 5 & 6 to their

normal Q/high and Q NOT/low outputs. As a consequence, the high activating

VSWR OVERLOAD light DS8 is removed turning off the front panel indicator.

A high now appears at PC4U2D-13 sending PC4U2A-3 and PC4U8A-1 in the

same direction after ramp-up circuit PC4R26/R27/CR1/CR17 charges. The

positive voltage at PC4J10-21 proceeds to LEVEL ADJUST R16 finally causing

buffer PC1U9 to release IF input attenuator PC1CR7/CR8 to normal attenuation.

This action brings the Exciter and transmitter out of standby by slowly increasing

the unit’s output power to normal.

J1 – 14 REFL PWR: No connection

J1 – 15 FWD PWR: A voltage proportional to the forward output power of the Exciter is

provided from Metering Detector A3J3-5 via PC4J9-5, PC4U5A and amplifier

PC4U7B whose gain is controlled by FWD PWR METER ADJ PC4R42. This

potentiometer is adjusted for PC4U7B to provide enough voltage for a 100%

reading on the front panel RF POWER meter DS9/10/11 when the Exciter is

providing its proper output power. This voltage is supplied to the meter through

PC4J10-15, squaring circuit U2, amplifier PC3U1 and LED Bar Graph Drivers

U4/U5/U6.

J1 – 16 LIN CORR ACTIVE: With Linearity corrector switch PC2S1 in the ENABLE

position +5V is presented to input pins 9 & 10 of PC4U1C via PC4J7-3. The

resulting high at PC4U1C-8 is forwarded to PC4J10-16, J1-16 and Q3 used to

turn on front panel LINEARITY CORRECTOR light DS3.

Control/Interface Board Interface (PC4J10)

Jack – Pin # Function

222

J1 – 17 PWR REF OUT: This voltage, proportional to the monitored output power,

originates from the front panel AGC ADJUST R15 and reaches PC1J6-8 of the

IF/Converter through PC4J10-17 and PC4J8-8. This signal acts as the power

reference for the IF/Converter’s output AGC loop by controlling variable

attenuator PC1CR9/CR10 and compensating for any power variations occurring

at the Exciter’s/transmitter’s output. If for some reason the Exciter’s/transmitter’s

output power were to drop, the positive voltage at PC4J8-8 would drop reducing

the attenuation provided by PIN diodes PC1CR9/CR10 in proportion to the power

decrease, thereby bringing the output power back to its appropriate operating

level. In the case where the Exciter’s/transmitter’s output increases above its

rated output, the PWR REFERENCE voltage at PC4J8-8 will increase causing

attenuator PC1CR9/CR10 to increase signal resistance, decreasing the output

level to its proper value.

J1 – 18 AGC/MANUAL LED: AGC ACTIVE LED DS6 will light when a high is present at

this input forward biasing transistor Q6 which is connected to PC4U4C-8 via R23.

Indicator DS6 will be lit only when concurrent highs are provided from the

OPERATE/SWEEP switch PC4S1 (OPERATE position), from the AMP STATUS

IN line at PC4J4-1, from the front panel AGC/MANUAL switch S2 (AGC position)

at PC4J10-9 and from the REMOTE AGC ON/OFF line at PC4J5-6, forcing the

output of PC4U4C high.

J1 – 19 PWR REF IN: This voltage, proportional to the monitored output power,

originates from either the Exciter (A3J3-5) or transmitter (A7A1J3-5) Metering

Detector and is buffered by PC4U5A or PC4U7A, respectively. The voltage is

forwarded to the front panel AGC ADJUST R15 through PC4JP1 and PC4J10-19

to variable gain amplifier U1. The amplitude of the voltage is controlled by R15

and reaches the IF/Converter through PCJ10-17 and PCJ8-8. The voltage acts

as the reference for the IF/Converter’s output AGC loop by controlling variable

attenuator PC1CR9/CR10 and automatically compensating for any power

variations occurring at the Exciter’s/transmitter’s output. If for some reason the

Exciter’s/transmitter’s output power were to drop, the positive voltage at PC4J8-8

would be reduced cutting the attenuation provided by PIN diodes PC1CR9/CR10

in proportion to the power decrease seen at the Exciter’s/transmitter’s output,

thereby bringing the power back to its appropriate operating level. In the case

where the transmitter’s output increases above its rated power, the PWR

REFERENCE voltage at PC4J8-8 will increase causing attenuator PC1CR9/

CR10 to add signal resistance, decreasing the Exciter’s/transmitter’s output level

to its proper value.

J1 – 20 SWEEP MODE LED: This input controls the operation of the front panel

SWEEP MODE LED DS4. With the OPERATE/SWEEP switch PC4S1 in the

SWEEP (low) position, PC4U3C supplies a low to PC4J10-20 and control

transistor Q4 which is forward biased to turn DS4. Placing switch PC4S1 in the

OPERATE position will generate a high causing the SWEEP MODE indicator to

go out.

Control/Interface Board Interface (PC4J10)

Jack – Pin # Function

223

J1 – 21 LEVEL ADJUST IN: Assuming the outputs of AND gates PC4U1A/U1B/U1D/

U2C/U2B/U2D/U2A are high, amplifier PC4U8A provides a reference of approxi-

mately 14V at this input which is fed to front panel LEVEL ADJUST potentiome-

ter R16. This potentiometer enables manual adjustment of IF/Converter variable

attenuator PC1CR7/CR8 and, therefore, manual control of the Exciter’s/

transmitter’s output power. If one of the above mentioned AND gates shifts low

due to a fault signal or command from:

J8-6 IF STATUS

S1 OPERATE/SWEEP

J6-3 2W AMPL STATUS

J2-8 LOCK STATUS

J9-1 REFL PWR

J5-1 REMOTE OP/STBY

J4-5 VIDEO SENSE

J10-7 OPERATE/STANDBY

then a negative voltage will emanate from PC4U8A and pass through

PC4J10-21, LEVEL ADJUST R16, J1-23, PC4J10-23, PC4J8-7, PC1J6-7 and

PC1U9-5, increasing the IF attenuation of PIN diodes PC1CR7/CR8 and

significantly reducing the output power of the Exciter/transmitter, placing the unit

in standby.

J1 – 22 SYNTH LOCK LED: This input controls the activation and deactivation of the

front panel SYNTHESIZER LOCK light DS2. The voltage originates at

A2A1J3-A as an operational indicator for the Synthesizer. A low (synthesizer

locked) from PC4J2-8 to the base of PC4Q1 will place a high at the inputs of

AND gate PC4U1A-1 & 2 forcing its output high. This high is passed through

PC4R5 and PC4J10-22 forward biasing Q2 causing DS2 to light. If Synthesizer

A2A1 unlocks, a high will be sent to PC4J2-8 which ultimately shuts off the

SYNTHESIZER LOCK indicator DS2.

J1 – 23 LEVEL ADJUST OUT: This voltage is developed in amplifier PC4U8A and sent

through LEVEL ADJUST R16 and passed from this output (J1-23) to PC4J8-7

as a control level for variable attenuator PC1CR7/CR8 in the IF/Converter (see

J1-21 above).

J1 – 24 IF STATUS LED: This signal is taken from the output of PC4U4B via resistor

PC4R19 to control IF STATUS LED DS5. With the presence of an IF signal at

the input of PC1, a high is provided from PC1U4A to PC4U4B, lighting IF

STATUS indicator DS5 via PC4R19, PC4J10-24 and control transistor Q5. If the

IF input is removed from PC1J1, PC1U4 will then provide a low to PC4U4B

extinguishing the IF STATUS LED DS5 while forcing U3D and U2A low.

J1 – 25 OUTPUT AGC VOLTAGE: This voltage drives the front panel AGC meter

DS12. From PC1J6-9, a ±15V signal is transformed to a 0 to +15V level by

PC4U8B and sent to PC4J10-25 and is used to drive the front panel AGC meter

employing LED Bar Graph Driver U3.

Control/Interface Board Interface (PC4J10)

Jack – Pin # Function

224

J1 – 26 AMPL STATUS LED: A high or low voltage at this pin originates from A1J3-3

to signal the status of the transistors within the 2W UHF Amplifier module. A

high at PC4J6-3 and PC4U3A-3 indicates that the amplifier devices are

operating properly while lighting AMPLIFIER STATUS LED DS1 via PC4R8,

PC4J10-26 and Q1. A low at the output of PC4U3A indicating a device failure

within the 2W Amplifier will extinguish the front panel AMPLIFIER STATUS

indicator DS1 via the same path.

2.2k 28V/15V/5V Power Supply:

Integrated Power Design SRW-65-4006-28 A2PS1

Input: TB1-L/N/G 85-264Vac / 47-63Hz / 128W

Outputs: TB2-1 15V @ 2A Max.

TB2-4 +15V @ 2A Max.

TB2-6 +28V @ 1A Max.

TB2-9 & 10 +5V @ 5A Max.

PS1 is a very compact, multioutput switching power supply capable of providing 65 watts of

maximum total output. It features a universal input with output overvoltage and overcurrent

protection. This supply powers all of the modules and PC boards within the Exciter drawer and is

not adjustable or field repairable. If found defective, PS1 must be returned to EMCEE for repair

or replacement.

2.3 500W UHF POWER AMPLIFIER DRAWER:

Interconnection Diagram 30394008/Rev 54 A3

Frequency Response 470-806MHz

RF In (J1) +18dBm peak visual

RF OUT (J2) +58dBm peak visual

Gain (J1-J2) 40dB +1/ 2dB

The TTU500FA transmitter is made up of one 500W Power Amplifier drawer (A3) containing two

300W Power Amplifier assemblies mounted on 14 by 16 inch fabricated high density heat sink

material. Both heat sink assemblies amplify an equal portion of the divided signal from Splitter

CP1 and provide approximately 300 watts of peak visual power at their outputs. Each assembly,

composed of dual parallel LDMOS transistors and a final stage built with four parallel high power

LDMOS devices. The first driver (Q1/Q3) is a Class A amplifier capable of 4 watts of peak visual

power and 18dB of gain. The second amplifier (Q5/Q6) is a Class AB driver delivering 14dB of

gain and a 40 watt peak capability. The final stage, providing 14dB of gain, is composed of four

120 watt devices (Q7/Q8/Q9/Q10) designed in a parallel push-pull configuration. The outputs of

the two 300 Watt Amplifier assemblies are summed in Combiner CP2 before exiting the drawer

at RF OUTput J2. The drawer’s monitoring circuits used to detect amplifier and power supply faults

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are contained on the Amplifier Status Interface board (PC1). Monitoring the operating temperature

of each 300 Watt Amplifier and the corresponding power supply control is furnished by the Power

Supply/Thermal Interface board PC2.

2.3a Power Splitter:

Schematic Diagram 10394220/Rev 51 A3CP1

Insertion Loss (J1-J2 & J3) 3.25dB

Frequency 470-806MHz

The Power Splitter is a Wilkinson design which divides the UHF signal from the Exciter drawer into

two signals of equal magnitude with 0 phase difference. These in-phase signals are used to

individually drive the two parallel 300 Watt UHF Power Amplifier assemblies (A1, A2).

2.3b 300W UHF Power Amplifier:

Schematic Diagram 40394135/Rev 56 A3A1, A3A2

Frequency Response 470-806MHz

RF IN (J1) +18dBm peak visual

RF OUT (J2) +58dBm peak visual

Gain (J1-J2) 40dB +1/ 2dB

Current Draw 22A @ 32V typical

Each 300W UHF Amplifier heat sink assembly consists of a 4 watt input driver stage, a 40 watt

intermediate driver stage and a 300 watt final amplifier, collectively providing approximately 40dB

of signal gain. To insure redundant operation, all amplifier stages utilize parallel transistors. The

input driver stage is built around LDMOS devices Q1/Q3, designed to supply 18dB of gain as

Class A amplifiers. Transistors Q2/Q4 furnish the appropriate bias and current regulation for the

RF devices with potentiometers R6/R7 set to supply 500mA of drain current to each. Capacitors

C3/C4/C5/C6 in conjunction with C50/C53 provide the proper input match for Q1/Q3. Coupling

capacitors C1/C2 bring in out-of-phase, equal amplitude signals from 90 hybrid coupler CP1 which

splits the input signal entering the amplifier at connector J1. Attenuator AT1 is selected to insure

that the gains of both 300W Amplifiers are matched within 0.5dB across the band of operation. At

the outputs of Q1/Q3 capacitors C15/C16/C17/C18/C19/C20 are part of microstrip matching

networks that couple the amplified signals into 90 hybrid combiner CP2. For maintenance and

troubleshooting purposes, SMA connector J3 is installed at the output of CP2 and connected via

jumper cable to the input of the intermediate driver amplifier.

The incoming signal at connector J4 is again split into equal amplitude, out-of-phase signals by

hybrid coupler CP3 and sent through two input matching networks composed of tuned microstrip

lines and capacitors C21 through C32. RF LDMOS transistors Q5/Q6 form a 40 watt class AB

amplifier featuring 14dB of gain. Both transistors receive drain current directly from the 32V supply

via 0.1 ohm bias resistors R130(A)/R121(D). To effectively measure the current through these

resistors, and therefore through each transistor, dc amplifiers U12/U11 monitor the voltage across

bias resistors R130/R121 producing a voltage at test points TP5/TP6. Each voltage will be

proportional to the drain current of the associated transistor using a ratio of 1V/100mA. Regulated

gate bias for each device is delivered from variable voltage regulator U13 which, through

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adjustment of R142, generates 10V gate bias to potentiometers R19/R23, each being set for

300mA drain consumption. At the drains of transistors Q5/Q6 microstrip elements in conjunction

with capacitors C37 to C42 and C47 to C52 form output matching structures to efficiently transfer

the amplified signals to hybrid coupler CP4. After in-phase combining, the signal is delivered to

SMA connector J2 which, in conjunction with J4, can be used for tuning and troubleshooting this

particular amplifier stage.

Jumper cable W2 transfers the signal from the intermediate driver to connector J1 of the final stage

where it is divided into equal amplitude components by an in-phase Wilkinson splitter terminated

with resistor R1. The resulting signals are passed to 90 hybrid couplers HY1/HY2 where they are

redivided and distributed to input baluns Z1/Z2/Z3/Z4 which transform the unbalanced signals into

the balanced form required by push-pull transistors Q7/Q8/Q9/Q10. After each balun, a series of

parallel capacitors form the input match for each transistor (e.g., C1/C2/C123/C7/C8/C9 for Q7)

with gate bias delivered from variable voltage regulators U7/U8/U9/U10. Using potentiometers R9/

R37/R55/R83, these regulators are set up to provide 10V to transistor bias adjustments R7/R25/

R30/R35/R53/R71/R76/R81, all calibrated to insure that both drains of each transistor conduct

500mA of idle current. Drain current for each side of transistors Q7 through Q10 is provided

directly from the amplifier’s 32V power supply via .05 ohm power resistors R13/R41/R59/R87 and

RF chokes L1/L2/L3/L4/L5/L6/L7/L8. Since only one drain bias resistor is employed for each

transistor, the transistor’s total current is monitored using dc amplifiers U1/U2/U3/U4 across each

bias resistor. At test points TP1/TP2/TP3/TP4, U1 through U4 will generate voltages proportional

to the total drain current of each transistor at a rate of 1V/1A. On the output side of each transistor

is a balanced matching structure composed of tuned lines and parallel capacitors (e.g., C10/C11/

C12/C127/C19/C20 for Q7) terminated in coaxial balun transformers Z5/Z6/Z7/Z8. The amplified

signals from Z5/Z6 are then combined in hybrid coupler HY3, as the signals from Z7/Z8 are

summed in coupler HY4. The two signals now formed in HY3 and HY4 are joined in the Wilkinson

combiner identified by termination resistor R139 at the amplifier’s output. From here the fully

amplified signal exits the 300 Watt Power Amplifier through connector J2.

For the purposes of troubleshooting and alignment, each parallel final amplifier centered on

transistors Q7/Q8/Q9/Q10 can be isolated by utilizing the SMA connectors provided at the input

and output of each circuit. For example, test point connections J3/J7 can be arranged as input and

output connectors for amplifier circuit Q7 by moving coupling capacitors C131/C21 to connect

J3/J7 directly to baluns Z1/Z5 while leaving the connections to hybrid couplers HY1/HY3 open.

The same can be done for amplifier circuit Q8 with C132-J4/C43-J8, for Q9 with C133-J5/C75-J9

and Q10 with C134-J6/C92-J10. To monitor the performance of transistors Q7 through Q10,

transistor fault circuits made up of comparators U6/U5 have been installed to monitor the ISOlation

ports of output hybrid combiners HY3/HY4. During normal transistor operation, the power entering

HY3/HY4 will be relatively balanced, causing very little power to be developed at the ISO port of

each combiner. However, if a transistor fails, the power imbalance at the input of the correspond-

ing hybrid will cause a significant power increase at its ISOlation port. After passing through

attenuator AT1/AT2, this excess power will be detected by diode CR1/CR2, filtered and delivered

as a dc voltage to comparator U6/U5. Under this circumstance, the voltage at pin 5 of U6/U5 will

exceed the reference at pin 6 supplied by potentiometer R103/R114 causing the comparator output

at pin 7 to go high. Normally, when transistors Q7 through Q10 are operating properly, this voltage

will be low. In either case, these amplifier STATUS voltages are sent to the Amplifier Status

Interface board (A3PC1) where they are ORed and forwarded to the transmitter’s Control/Monitor

board (A5PC1).

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2.3c Power Combiner:

Schematic Diagram 10394221/Rev 51 A3CP2

Insertion Loss (J1-J2 & J3) 3.25dB

Frequency 470-806MHz

The Power Combiner is a standard Wilkinson circuit that combines the two amplified signals from

the 300 Watt Power Amplifier assemblies (A1, A2). The recombined signal is then brought to the

drawer’s output connector and applied to the UHF Bandpass Filter (A7FL1) located in the

transmitter Output Section.

2.3d Amplifier Status Interface:

Schematic Diagram 20394216/Rev 53 A3PC1

The Amplifier Status Interface board monitors two critical areas in the 500 Watt Power Amplifier

drawer: the 32V Power Supply outputs and the 300W Amplifier operational status. The Status

board receives power from the two 32V Power Supplies (PS1/PS2) within the amplifier drawer

through inputs J1-1 & 2 and diodes CR1/CR2. Voltage divider resistors R4/R5 provide a 14V

reference at pins U1A-3/U1B-5 which, assuming both power supplies are operating properly, are

compared to the 16V inputs present at U1A-2/U1B-6 via dividers R2/R3 and R1/R6. In this

situation, output pins U1-1 & 7 are negative forcing U2B-7 positive and forward biasing Q1A. The

ground appearing at J1-3 is relayed to the Control/Monitor board (A5PC1) illuminating the POWER

SUPPLY LED on the transmitter’s Control/Metering panel via A3J3-6 and A5PC1J1-6/A5PC1J2-6.

If either one of the power supply outputs drops below 28V, U1A-1/U1B-7 will turn positive, creating

a negative at the base of Q1A through U2B, shutting off the Control/Metering POWER SUPPLY

indicator. Concurrently, a low will be sent to the IF/Converter Output AGC Control (PC1J6-10)

from the Control/Metering panel, disabling the circuit so that the transmitter can continue to operate

at a lower power.

The second function of this board is to monitor the operation of each 300 Watt Power Amplifier

assembly. When operating properly, low voltages are forwarded from the amplifier transistor

output monitor circuits at A1TB1-4/A2TB1-4 to J1-5/J1-6. Comparator U2A will supply a low at

pin 1 keeping control transistor Q1B reverse biased, FAULT OUT line J1-4 high and Control/

Metering AMPLIFIER indicator (A5PC1DS1) lit. If a transistor in one of the 300W Amplifier’s

happens to fail, a high will be generated at either A1TB1-4 or A2TB1-4 and at J1-5 or J1-6, pushing

the output of U2A high and biasing transistor Q1B into conduction. The short created at J1-4 will

extinguish the AMPLIFIER indicator located on the transmitter’s Control/Metering panel. As before,

a low will be sent to the IF/Converter Output AGC Control line (PC1J6-10) from the Control/

Metering panel, disabling the AGC circuit so that the transmitter will continue to operate at reduced

power.

2.3e Power Supply/Thermal Interface:

Schematic Diagram 30400055/Rev 52 A3PC2

The purpose of the Power Supply/Thermal Interface board is to monitor the thermostats (A1S1/

A2S1) on each 300 Watt Amplifier assembly and activate the associated power supply if the

228

amplifier’s operating temperature is correct. Normally the thermostats will present a ground to

J1-5/J1-7 while Control/Monitor transistors A5PC1Q1/Q2 provide open/ENABLE signals to J1-4/

J1-8 due to the high sent on the Exciter’s AMP BIAS CONTROL line (A5PC1J3-3). NAND gates

U1/U2 will supply highs to transistors Q2/Q5, reverse biasing transistors Q3/Q6 which then supply

highs to U1-10/U1-4/U1-5/U2-10. With high ENABLE signals at J1-4/J1-5 and low THERMAL

STATUS signals at J1-5/J1-7, outputs U1-8/U1-6/U2-8 are now low, cutting off control transistors

Q7/Q8/Q9. The opens presented to PS1J3-7/PS2J3-7 by Q7 and Q9 will activate both power

supplies turning on the two 300W Amplifiers (A1/A2) and, therefore, the 500 Watt Power Amplifier

drawer. Concurrently, the open presented by Q6 will keep the respective Control/Metering

AMPLIFIER TEMP indicator inactive via J1-6, J3-4, A5PC1J1-4 or J2-4 and A5PC1Q9 or Q10.

If an overtemperature condition arises on one of the 300W Amplifier assemblies causing the

attendant 175 F thermostat to open, a high will occur at either J1-5 or J1-7. Assuming the thermal

problem resides in AMPL 1, pin 11 of gate U1 will now go low, reverse biasing Q2 and forward

biasing Q3. The resulting high at U1-8 will cause Q7 to conduct, providing a ground at J1-3 which

will shut down the 32V Supply (PS1) powering AMPL 1 (A1). To avoid cycling the affected

amplifier back on as it cools, capacitor C3 charges with the appearance of a high at the collector

of Q2 placing a permanent ground latch on the base of Q2 through forward biased Q1. (This

thermal overload latch can only be removed by opening the transmitter’s front panel AC POWER

circuit breaker CB1). At the same time, the low at the collector of Q3 has forced U1-6 high causing

transistor Q8 to place a ground at J1-6. This low TEMP STATUS signal is sent to A3J3-4 and

A5PC1J1-4 turning on the AMPLIFIER TEMPERATURE indicator (A5PC1DS10) using A5PC1Q9.

Also, the low now appearing at A5PC1U1D-12 will produce a low at A5PC1J3-1 which is eventually

seen at the IF/Converter Output AGC Control (PC1J6-10), disabling the AGC circuit so that the

transmitter can operate at a reduced power commensurate with an inactive 300 Watt Power

Amplifier.

2.3f 32V Power Supply:

Vicor PM1-02-520PFC A3PS1, A3PS2

Output +32V @ 31 Amps

Power Factor .99 @ 800W

Efficiency 80%

The 32V Power Supply is a single output, high efficiency, 1000 watt switching supply featuring

power factor correction and a volumetrically pleasing package. Each supply is connected directly

to its allocated 300W UHF Power Amplifier assembly and is activated/deactivated through the use

of open/short logic levels provided by the Power Supply/Thermal Interface board. These logic

levels are connected to J3-7, the GSD (General Shut Down) input of each supply.

The 32V Power Supply is not field repairable. If defective, it should be returned to EMCEE for

repair or replacement.

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2.4 OUTPUT SECTION:

Interconnection Diagram 40400003/Rev 52 A7

The Output Section of the TTU500FA Transmitter is located at the top of the transmitter cabinet

behind the Control/Metering Panel (A5). This assembly constitutes the transmitter’s RF output and

contains the Bandpass Filter (FL1), Directional Coupler (DC1) and the Metering Detector (A1).

2.4a UHF Bandpass Filter:

Schematic Diagram N/A A7FL1

Frequency Response 6MHz @ 1dB

Insertion Loss (J1-J2) 0.5dB

Rejection 25dB @ 4.5MHz FV/+4.5MHz FA

The UHF Bandpass Filter is a highly selective, low loss coaxial cavity design composed of six

tuned sections, four utilized for band selection and two employed for band rejection. The two band

rejection cavities, physically located at each end of the filter, provide 25dB bandstop notches

positioned on the 4.5MHz visual and aural out-of-band products generated through common

amplification of the television signal. This filter also aids significantly in the attenuation of channel

related harmonics. Unless a network analyzer and knowledgeable technician/engineer are

available, it is recommended that this filter be returned to the factory for repair and/or

retuning.

2.4b Directional Coupler:

Schematic Diagram N/A A7DC1

Frequency Range 460-890MHz

Insertion Loss (J1-J2) 0.25dB

FWD Coupling (J1-J3) 46dB ± 1dB

REFLD Coupling (J1-J4) 46dB ± 1dB

The Directional Coupler is a high power, four-port circuit connected directly to the output of the

UHF Bandpass Filter (FL1) using 7/8" EIA flange assemblies for input and output connections (J1,

J2). The forward (FWD, J3) and reflected (REFLD, J4) coupled ports are made up of “N”

connectors which deliver RF samples of the transmitter’s output to the Metering Detector (A1). DC

signals, proportional to the transmitter’s forward and reflected output power, are then sent to the

Control/Monitor board (A5PC1) to drive the RF POWER meter on the Control/Metering panel.

2.4c Metering Detector:

Schematic Diagram 30400038/Rev 53 A7A1

The Metering Detector contains two identical circuits for monitoring the transmitter’s forward and

reflected output power while providing dc voltages proportional to those signal levels. Each output

230

sample from the Directional Coupler (DC1) is supplied to the FORWARD SAMPLE input (J1) and

the REFLECTED SAMPLE input (J2) of the detector. The signals are passed through resistive

attenuators R1/R2/R3, R9/R10/R11 and coupling capacitors C1, C7 to RMS detectors U1, U3. At

pin 7, U1 and U3 output the video component of the incoming UHF visual carriers while C3 and

C9 roll off the aural energy contained in each signal. The amplitude of the video is then doubled

using op-amps U2 and U4 and sent to peak detectors CR1/CR2 via pins 1 and 2 of jumpers JP1

and JP2. (Pins 2 and 3 of JP1 and JP2 are utilized for average digital power detection only.)

Capacitors C4/C10 and resistors R7/R15 filter the peak video component from diodes CR1/CR2

and each dc voltage is sent to unity gain buffers U2/U4. The dc levels at pin 7 of U2 and U4 are

now proportional to the peak forward or reflected power of the respective visual signals entering

the Metering Detector. These voltages will be delivered to the Control/Monitor board (A5PC1) to

provide FWD and REFL readings on the RF POWER meter mounted on the Control/Metering

panel (A5).

2.5 CONTROL/METERING PANEL:

Interconnection Diagram 40400003/Rev 52 A5

The Control/Metering panel displays various fault indicators and output power metering for the

TTU500FA Transmitter. The panel is located at the top front of the transmitter cabinet and

includes the Control/Monitor board (PC1) and a ±5V/±15V Power Supply (PS1), both mounted on

the rear of the panel.

2.5a Control/Monitor Board:

Schematic Diagram 40400045/Rev 55 A5PC1

The Control/Monitor board, mounted on the rear side of the Control/Metering panel (A5) is the

control center for the TTU500FA Transmitter. All local and remote monitoring signals, control

voltages and interlock circuits are routed to their proper destination through this circuit board. Also,

the transmitter’s forward and reflected output power metering is controlled and displayed on this

board. Each multipin connector on the Control/Monitor is dedicated to an individual drawer or

assembly as described below.

500W Power Amplifier Interface (A3J3)

Jack – Pin # Function

J1 – 5 PWR AMPLIFIER FAULT: This voltage is brought in from the Amplifier Status

Interface board located in the 500 Watt Amplifier drawer A3 through A3PC1J1-4

and A3J3-5, indicating that one of the 300W Amplifier (A3A1/A3A2) assemblies

has had an output transistor failure. Under normal operation this voltage will be

high forcing a high from U1A-3 which forward biases Q5, lighting AMPLIFIER

STATUS indicator DS1. In case of a transistor failure in drawer A3, this line will

go low driving U1A-3 low to turn off indicator DS1, but also causing AND gates

U1C, U2D and U1D to send a low to J3-1, the AMP STATUS output. This low

signal is forwarded to the Exciter drawer at A2J4-1 and on to the IF/Converter

Output AGC Control line (PC1J6-10) disabling the IF output AGC circuit so that

the transmitter continues to operate at reduced power.

500W Power Amplifier Interface (A3J3)

Jack – Pin # Function

231

J1 – 7 +5V: From PS1J2-2

J1 – 6 POWER SUPPLY OK: This input is the status monitor line for the two 32V

Power Supplies (A3PS1/A3PS2) contained in amplifier drawer A3. This line

originates from the Amplifier Status Interface board at A3PC1J1-3 and is low

when both power supplies are operating normally, forward biasing transistor Q3

which supplies a high collector to U1B-4 & 5. The high output on U1B-6 will

make control transistor Q6 conduct turning on AMPLIFIER POWER SUPPLY

light DS2. If one of the power supply outputs drops below 28 volts, this line will

shift high shutting off power supply indicator DS2. Concurrently, a low will be

sent via U1C-8, U2D-11, U1D-11 and J3-1 to the Exciter’s Control/Interface

board at A2PC4J4-1. From here the signal finds the IF/Converter Output AGC

Control at PC1J6-10 from A2PC4J8-10, disabling the AGC so that the transmitter

can continue to operate at a lower power.

J1 – 4 THERMAL STATUS: This control signal is generated on the Power Supply/

Thermal Interface board (A3PC2) which monitors the thermostats fastened to

each 300W Amplifier heat sink (A3A1/A3A2) located in the 500W Power

Amplifier drawer. The circuit provides an open/high under normal amplifier

operating temperatures while supplying a short/low during overtemperature situ-

ations. With an open connected to base resistor R44, transistor Q9 is cutoff

extinguishing AMPLIFIER TEMPERATURE LED DS10. If one of the 300W heat

sinks becomes too hot ( 175 F), opening its associated thermostat, the Thermal

Interface board will develop a short at R44 turning on Q9 and indicator DS10 as

notification that an overtemperature situation has occurred. Aside from the

appropriate power supply being deactivated, the low at R44 will shift the output

of gate U1D presenting a low at J3-1, the AMP STATUS output. As stated

previously, this signal is sent to the IF/Converter Output AGC Control via

A2PC4J4-1, A2PC4J8-10 and A2PC1J6-10 to disable the AGC circuit so that the

transmitter operates at a reduced power commensurate with an inactive

300 Watt Power Amplifier.

J1 – 2 PS1 ENABLE: This output, sent to the Power Supply/Thermal Interface board

(A3PC2), is the control signal necessary to activate or deactivate 32V Power

Supply A3PS1. Control transistor Q1A provides an open (PS1 on) or short (PS1

off) as dictated by op-amp U3 which receives its instructions directly from the

Exciter’s AMP BIAS CONTROL appearing at J3-3 from A2J4-3. Power supply

activation requires a high at U3-2 which will appear when the Exciter’s UHF

Synthesizer A2A2 is locked (A2PC4U1A high), when the OPERATE/STANDBY

switch is in OPERATE (A2PC4U1D-11 high) and when the VIDEO SENSE line

is high (A2PC4U2C high) indicating video present at the modulator. The PS1

ENABLE open/high provided by Q1A will be seen at the Power Supply/Thermal

Interface board input A3PC2J1-4 turning on power supply A3PS1 assuming an

overtemperature condition has not occurred as indicated by a high (open

thermostat) at A3PC2J1-5.

500W Power Amplifier Interface (A3J3)

Jack – Pin # Function

232

J1 – 3 PS2 ENABLE: This output, sent to the Power Supply/Thermal Interface board

(A3PC2), is the control signal necessary to activate or deactivate 32V Power

Supply A3PS2. Control transistor Q1B provides an open (PS2 on) or short (PS2

off) as dictated by op-amp U3 which receives its instructions directly from the

Exciter’s AMP BIAS CONTROL appearing at J3-3 from A2J4-3. Power supply

activation requires a high at U3-2 which will appear when the Exciter’s UHF

Synthesizer A2A2 is locked (A2PC4U1A high), when the OPERATE/STANDBY

switch is in OPERATE (A2PC4U1D-11 high) and when the VIDEO SENSE line

is high (A2PC4U2C high) indicating video present at the modulator. The PS2

ENABLE open/high provided by Q1B will be seen at the Power Supply/Thermal

Interface board input A3PC2J1-8 turning on power supply A3PS2 assuming an

overtemperature condition has not occurred as indicated by a high (open thermo-

stat) at A3PC2J1-8.

J1 – 1 GND: From J7-4

Video Detector Switch Interface (A9J1)

Jack – Pin # Function

J8 – 1 VIDEO SENSE: A high or low indication for the presence or absence of video

programming is delivered to this input from the Video Detector Switch (VDS)

TALLY jack. With video present at INPUT A9-A of the VDS, an open is sent

from A9J1-NO to J8-1 and is looped to J3-5 placing a high on the Exciter’s

Control/Interface gate A2PC4U2C-10. If a loss of video occurs, a ground

appears at A9J1-NO forcing A2PC4U2C low at pins 10 & 8. This low appears at

AMP BIAS CONTROL input J3-3 from A2PC4J4-3 deactivating power supplies

A3PS1/PS2 in the 500W UHF Power Amplifier drawer A3.

J8 – 4 GND: From A9J1-COM

Exciter Interface (A2J4)

Jack – Pin # Function

J3 – 1 AMP STATUS: A power supply failure (U1B or U2B low), an overtemperature

condition (U1D low) or an output transistor failure (U1A or U2A low) occurring in

the 500W UHF Power Amplifier (A3) will result in a low at this pin. The resulting

lows at A2PC4U4A-3/U4D-11/U4C-8 are sent through A2PC4J8-10 to

IF/Converter switch A2PC1S2 which determines if the IF output AGC is active

(high) or fixed (low). With a low at A2PC1S2-6, pins 1 & 2, 3 are closed placing

a ground on A2PC1U18-3. This low forces PIN diodes PC1CR9/CR10 to

stabilize at the center of their attenuation range ( 3dB). At the same time, the

low output of AND gate A2PC4U4C is passed to pin A2PC4J10-18 and on to

Exciter front panel AGC ACTIVE LED control transistor A2PC3Q6. Since the

low will not allow A2PC3Q6 to conduct, A2PC3DS6 will turn off indicating an

inactive output AGC. If the voltage was high, transistor A2PC3Q6 would forward

bias causing the LED to turn on, indicating the output AGC is active.

Exciter Interface (A2J4)

Jack – Pin # Function

233

J3 – 5 VIDEO SENSE: A high or low indication for the presence or absence of video

programming is delivered to this output from the Video Detector Switch (VDS)

TALLY jack via J8-1. With video present at INPUT A9-A of the VDS, an open

is sent from A9J1-NO to J8-1 and is looped to J3-5 placing a high on the

Exciter’s Control/Interface input A2PC4J4-5 and gate A2PC4U2C-10. If a loss

of video occurs, a ground appears at A9J1-NO forcing A2PC4U2C low at pins

10 & 8. This low appears at AMP BIAS CONTROL input J3-3 from A2PC4J4-3

deactivating power supplies A3PS1/PS2 in the 500W UHF Power Amplifier.

J3 – 3 AMP BIAS CONTROL: This control voltage is generated on the Exciter’s

Control/Interface board (A2PC4) and forwarded to this input pin from

A2PC4J4-3. Its purpose is to activate or deactivate the power supplies (A3PS1/

PS2) contained within the 500W UHF Power Amplifier drawer A3. Power supply

activation requires a high at U3-2 which will appear when the Exciter’s UHF

Synthesizer A2A2 is locked (A2PC4U1A high), when the OPERATE/STANDBY

switch A2PC3S1 is in OPERATE (A2PC4U1D-11 high) and when the VIDEO

SENSE line A9J1-NO is high (A2PC4U2C high) indicating video present at the

modulator. The resulting low output at U3-1 will back bias switching transistors

Q1A/B and Q2A/B providing an open/high to the Power Supply/Thermal

Interface board A3PC2 turning on power supplies A3PS1/PS2 in the 500W

Power Amplifier drawer. If any of the above conditions change creating a logic

low at J3-3, then the 500W UHF Power Amplifier will be shut down.

J3 – 8 GND: From A2J4-8

Audio/Video/Remote Panel Interface (A8J1)

Jack – Pin # Function

J4 – 1 REFLECTED POWER: This voltage, proportional to the reflected power seen

at the output of the transmitter, is provided for monitoring at REMOTE plug

A8J1-1 on the rear Video/Audio/Remote panel. The voltage is taken from output

pin 7 of meter adjust amplifier U5B which is primarily used to drive the RF

POWER meter DS5/DS6/DS7 mounted on the Control/Metering front panel via

FWD/REFL switch S1. The gain of U5B is controlled by the setting of poten-

tiometer R32 and receives its reflected power voltage from Metering Detector

output A7A1J3-1 via REFLECTED POWER INPUT J6-1. With S1 in the REFL

position, the information supplied by U5B is fed from S1-2 & 1 to four quadrant

multiplier U10 which squares the voltage so that the bar graph will respond as a

power meter rather than a volt meter. The signal is then amplified by U6A

before distribution to bar graph drivers U7/U8/U9. With the TTU500FA trans-

mitter operating at its rated power and REFLECTED POWER LED DS9 lit, REFL

METER ADJUST R32, accessible through the Control/Metering panel, is

adjusted for a 100% indication on the RF POWER meter with a simulated open

at the transmitter’s output (total output power returned).

J4 – 3 FWD POWER: This voltage, presented at the Video/Audio/Remote panel

REMOTE plug A8J1-3 for monitoring, is proportional to forward power produced

at the transmitter’s output. The voltage is generated at meter adjust op-amp

U5A-1 which receives its input from Metering Detector A7A1-5 through

Audio/Video/Remote Panel Interface (A8J1)

Jack – Pin # Function

234

FORWARD POWER INPUT J6-5. The output voltage of U5A is also used to

provide a reading on the Control/Metering RF POWER bar graph meter through

the FWD/REFL front panel switch S1. For further explanation see J5-7 below.

J4 – 2 AGC VOLTAGE: This is the same voltage that drives the AGC meter

(A2PC3DS12) located on the front panel of the Exciter drawer. This potential,

a representation of the IF/Converter output AGC voltage, is taken from Control/

Interface amplifier A2PC4U8B and made available for monitoring at REMOTE

jack A8J1-2 via A2PC4J5-4 and J5-4.

J4 – 6 REMOTE VSWR RESET: This input control originates at REMOTE jack A8J1-6,

loops through J5-5 to the Exciter Control/Interface input A2PC4J5-5 and on to

VSWR overload flip-flop reset pin A2PC4U9A-4. A momentary ground would

normally be applied to this line bringing the transmitter out of standby due to a

VSWR overload created by excessive returned power at the output of the unit.

(A momentary ground is also provided by Exciter front panel VSWR RESET

switch A2PC3S3.) The transition from high to low on pin 4 of flip-flop

A2PC4U9A will reset pins 5 & 6 to their original Q (high) and Q NOT (low) states,

removing the low from A2PC4U2D-13 and the high from VSWR OVERLOAD

LED control transistor A2PC3Q8, respectively. Exciter front panel LED

A2PC3DS8 will then turn off and IF input attenuator A2PC1CR7/CR8 will be

returned to normal operating levels.

J4 – 7 REMOTE AGC ON/OFF: This input control begins at REMOTE jack A8J1-7

and, by applying a ground, this pin can be used to deactivate the voltage that

controls IF/Converter output AGC attenuator A2PC1CR9/CR10. From J4-7, this

ground will be looped through J5-6 and sent to A2PC4J5-6. The low now found

at A2PC4U4D-12 will force A2PC4U4C-8 and A2PC4J8-10 low driving the

IF/Converter PIN diodes A2PC1CR9/CR10 to stabilize at the center of their

attenuation range ( 3dB). With the output of A2PC4U4C at a logic low, that sig-

nal is also sent to pin A2PC4J10-18 and on to front panel AGC ACTIVE LED

A2PC3DS6. Since the voltage at A2PC3J1-18 is low, A2PC3Q6 will not conduct

and A2PC3DS6 will not illuminate indicating an inactive output AGC.

J4 – 5 REMOTE OP/STBY: This pin is connected to the Video/Audio/Remote panel

plug A8J1-5 which is normally left open allowing the high to remain at J5-1,

A2PC4J5-1 and A2PC4U1D-13 keeping the transmitter in operation. If the oper-

ator wishes to place the Exciter and transmitter in standby from a remote

location, a ground is applied to this line forcing output A2PC4U1D-11 to go low,

causing succeeding AND gates A2PC4U1B through A2PC4U2A to send a low to

the input of A2PC4U8A-3 and output A2PC4J4-3. The low forwarded to

A2PC4J10-21 will eventually enter the IF/Converter at A2PC1-7 via A2PC4J8-7

causing buffer A2PC1U9 to set IF attenuator A2PC1CR7/CR8 to maximum

attenuation preventing the Exciter from radiating a signal. Concurrently, the low

at A2PC4J4-3 will appear at J3-3 forcing U3 to shut down the 500W Power

Amplifier drawer power supplies (A3PS1/PS2). The transmitter is now in standby

prevented from radiating a signal.

J4 – 8 GND: From J7-4

235

Exciter Remote Interface (A2J5)

Jack – Pin # Function

J5 – 1 REMOTE OP/STBY: This control pin is looped through J4-5 and connected to

pin 5 of REMOTE plug A8J1 to remotely control the operate/standby function of

the transmitter. See the function description of J4-5 above for further

information.

J5 – 3 REFLECTED POWER: This voltage, brought into the Control/Monitor board

from Metering Detector A7A1J3-1 via J6-1 and buffered by U4B, is proportional

to any reflected power present at the transmitter’s output. Sent from J5-3 to

A2PC4J5-3, this voltage is monitored by comparator A2PC4U6A for an exces-

sive returned power indication at pin 3 which could exceed the reference at pin 2,

a level determined by VSWR OVLD REF potentiometer A2PC4R12 (25% of the

transmitter’s forward rating). With high VSWR, output pin A2PC4U6A-1 will turn

positive causing output pins 5 & 6 of flip-flop A2PC4U9A to change polarity. As

A2PC4U9A-5 goes negative, gate A2PC4U2D will output a low on pin 11 sending

A2PC4U2A-3 and A2PC4U8A-1 low. The low at A2PC4J10-2 proceeds to

A2PC3J1-21, LEVEL ADJUST A2PC3R16, A2PC3J1-23, A2PC4J10-23,

A2PC4J8-7 and A2PC1-7, causing buffer A2PC1U9 to set IF input attenuator

A2PC1CR7/CR8 at maximum attenuation. This action reduces the output power

of the Exciter and transmitter approximately 50B to insure that no amplifier

damage occurs due to excessive output VSWR. Concurrently, the high

generated at A2PC4U9A-6 is used to light VSWR OVERLOAD indicator

A2PC3DS8 via A2PC4J10-11, A2PC3J1-11 and transistor A2PC3Q8.

J5 – 4 AGC VOLTAGE: This is the same voltage that drives the AGC meter

(A2PC3DS12) located on the front panel of the Exciter drawer. This voltage is

a representation of the IF/Converter output AGC voltage taken from Control/

Interface amplifier A2PC4U8B and made available for monitoring at REMOTE

jack A8J1-2 via A2PC4J5-4, J5-4 and J4-2.

J5 – 6 REMOTE AGC ON/OFF: This control begins at REMOTE jack A8J1-7 and, by

applying a ground to this pin, the voltage that controls IF/Converter output AGC

attenuator A2PC1CR9/CR10 will be deactivated. This ground will be looped

through J5-6 from J4-7 and sent to A2PC4J5-6. The low now found at gate

A2PC4U4D-12 will shift A2PC4U4C-8 and A2PC4J8-10 low, forcing IF/Converter

PIN diodes A2PC1CR9/CR10 to stabilize at the center of their attenuation range

(3dB). With the output of A2PC4U4C at a logic low, that signal is also sent to

pin A2PC4J10-18 and on to front panel AGC ACTIVE LED A2PC3DS6. Since

the voltage at A2PC3J1-18 is low, A2PC3Q6 will not conduct and A2PC3DS6 will

not illuminate indicating an inactive output AGC.

J5 – 5 REMOTE VSWR RESET: This control originates at REMOTE jack A8J1-6,

loops through from J4-6 to the Exciter Control/Interface input A2PC4J5-5 and on

to VSWR overload flip-flop reset pin A2PC4U9A-4. A momentary ground would

normally be applied to this line to bring the transmitter out of standby due to a

VSWR overload created by excessive returned power at the output of the unit.

(A momentary ground is also provided by Exciter front panel VSWR RESET

switch A2PC3S3). The transition from high to low on pin 4 of flip-flop

A2PC4U9A will reset pins 5 & 6 to their original Q (high) and Q NOT (low) states,

removing the low from A2PC4U2D-13 and the high from VSWR OVERLOAD

LED control transistor A2PC3Q8, respectively. Exciter front panel LED

Exciter Remote Interface (A2J5)

Jack – Pin # Function

236

A2PC3DS8 will then turn off and IF input attenuator A2PC1CR7/CR8 will be

returned to normal operating levels.

J5 – 7 FWD POWER: The outgoing voltage at this pin from buffer U4A is proportional

to the forward output power of the transmitter according to the voltage supplied

by Metering Detector A7A1J3-5 via FORWARD POWER INPUT J6-5. This

metering information is then forwarded through A2PC4J5-7 to pin 3 of buffer

A2PC4U7A. When the Exciter is driving higher power equipment, as in the

TTU500FA, pins 1 & 3 of jumper A2PC4JP1 are closed sending the metering

voltage from A2PC4U7A to the front panel AGC ADJUST amplifier A2PC3U1

through A2PC4J10-19 and A2PC3J1-19. From AGC ADJUST PC3R15, this

PWR REFERENCE signal reaches A2PC1J6-8 of the IF/Converter by

A2PC3J1-17, A2PC4J10-17 and A2PC4J8-8. This voltage now acts as the

reference for the IF/Converter’s output AGC loop by controlling variable

attenuator A2PC1CR9/CR10 and compensating for any power variations occur-

ring at the transmitter’s output. At the same time, the voltage at J6-5 is supplied

to FORWARD POWER meter adjust amplifier U5A, the gain of which is dictated

by the setting of potentiometer R31. Connected to front panel FWD/REFL meter

switch at S1-3, the output of U5A is essentially utilized to deflect the RF POWER

bar graph meter DS5/DS6/DS7 when S1 is in the FWD position. The information

supplied by U5A is fed from S1-3 & 1 to four quadrant multiplier U10 which

squares the voltage so that the bar graph will respond as a power meter rather

than a volt meter. The signal is then amplified by U6A before distribution to bar

graph drivers U7/U8/U9. With the TTU500FA transmitter operating at its rated

power and FORWARD POWER LED DS8 lit, FWD METER ADJUST R31,

accessible through the Control/Metering panel, is adjusted for a 100% indication

on the RF POWER meter.

J5 – 8 GND: From A2J5-8

Power Supply Interface (PS1J2)

Jack – Pin # Function

J7 – 1 +5V: From PS1J2-3

J7 – 2 15V: From PS1J2-6

J7 – 3 +15V: From PS1J2-1

J7 – 4 GND: From PS1J2-5

Metering Detector Interface (PS1J2)

Jack – Pin # Function

J6 – 5 FORWARD POWER INPUT: This input voltage is proportional to the power

being produced at the RF OUTput of the transmitter (A7DC1J2) and is supplied

by the Metering Detector’s FWD PWR connection A7A1J3-5. The signal is then

supplied to buffer amplifier U4A and FORWARD POWER meter adjust amplifier

Metering Detector Interface (PS1J2)

Jack – Pin # Function

237

U5A. The voltage provided at U4A to J5-7 will act as the reference for the

IF/Converter’s output AGC loop by controlling variable attenuator A2PC1CR9/

CR10 and compensating for any power variations occurring at the transmitter’s

output. At the same time, the voltage from amplifier U5A, its gain dictated by

the setting of potentiometer R31, is connected to front panel FWD/REFL meter

switch at S1-3 and is utilized to deflect the RF POWER bar graph meter DS5/

DS6/DS7 when S1 is in the FWD position. The information supplied by U5A is

fed from S1-3 & 1 to four quadrant multiplier U10 which squares the voltage in

order that the bar graph responds as a power meter rather than a volt meter.

The signal is then amplified by U6A before distribution to bar graph drivers U7/

U8/U9. With the TTU500FA transmitter operating at its rated power and

FORWARD POWER LED DS8 lit (S1-4 & 6 closed) FWD METER ADJUST R31,

accessible through the Control/Metering panel, is adjusted for a 100% indication

on the RF POWER meter.

J6 – 4 GND: From J7-4

J6 – 3 +5V: From J7-1

J6 – 1 REFLECTED POWER INPUT: This voltage, brought in from Metering Detector

A7A1J3-1, is proportional to any reflected power present at the transmitter’s

output. The signal buffered by U4B is sent from J5-3 to A2PC4J5-3, to be moni-

tored by VSWR overload comparator A2PC4U6A on the Exciter’s Control/

Interface board. If the comparator reference (A2PC4R12) is exceeded due to

excessive reflected power at the transmitter’s output, the power from the Exciter

and transmitter will be reduced by approximately 50dB to insure that no damage

occurs to the final amplifier (A3). Concurrently, VSWR OVERLOAD indicator

A2PC3DS8 on the Exciter’s front panel will light. The voltage at J6-1 is also

connected to the REFLECTED POWER meter adjust amplifier input U5B-5. The

output at U5B is primarily used to drive the RF POWER meter DS5/DS6/DS7 via

FWD/REFL switch S1, both mounted on the Control/Metering front panel. With

S1 in the REFL position, the information supplied by U5B is fed from S1-2 & 1

to four quadrant multiplier U10 which squares the incoming voltage so that the

bar graph will respond as a power meter rather than a volt meter. The signal is

then amplified by U6A before distribution to bar graph drivers U7/U8/U9. With

the TTU500FA transmitter operating at its rated power and REFLECTED

POWER LED DS9 illuminated (S1-5 & 4 closed), REFL METER ADJUST R32,

accessible through the Control/Metering panel, is adjusted for a 100% indication

on the RF POWER meter with a simulated open at the transmitter’s output (total

output power returned).

iii

SECTION III

MAINTENANCE

3.1 PERIODIC MAINTENANCE SCHEDULE ................................. 3 1

3.2 RECOMMENDED TEST EQUIPMENT ................................... 3 1

3.3 TROUBLESHOOTING .................................................. 3 2

3.3a Control/Metering Panel Indicators ....................................... 3 2

3.3b EMEX1 Exciter Drawer Indicators ....................................... 3 3

3.3c Troubleshooting Chart ............................................... 3 5

3.4 ALIGNMENT ........................................................... 3 7

3.4a Exciter UHF Bandpass Filter .......................................... 3 7

3.5 OUTPUT POWER CALIBRATION ....................................... 3 7

3.5a Forward Power ..................................................... 3 8

3.5b Reflected Power (Optional) ............................................ 3 9

3.6 LINEARITY CORRECTOR ADJUSTMENT ............................... 3 9

3.7 REMOTE MONITOR SIGNAL LEVELS .................................. 3 11

3.8 SPARE MODULES AND COMPONENTS .................................S 1

3.9 SYNTHESIZER PROGRAMMING

3 1

SECTION III

MAINTENANCE

3.1 PERIODIC MAINTENANCE SCHEDULE:

OPERATION RECOMMENDATION

ALIGNMENT Upon installation and at one-year intervals

thereafter (Section 3.4).

OUTPUT POWER CALIBRATION Same as above (Section 3.5).

FANS Inspect as often as possible (at least monthly)

and clean when necessary. No lubrication

needed.

3.2 RECOMMENDED TEST EQUIPMENT:

EQUIPMENT MANUFACTURER MODEL #

Digital Multimeter HEWLETT PACKARD E2378A

Oscilloscope TEKTRONIX 2232

VHF Sweep Generator WAVETEK 2001

50 Ohm RF Detector TELONIC BERKELEY 8553

20dB/30dB Attenuator NARDA 766-20/30

30dB Directional Coupler NARDA 3001-30

50 Ohm, 500W Dummy Load NARDA 785-30

Power Meter HEWLETT PACKARD 435B

Frequency Counter HEWLETT PACKARD 5386A

Spectrum Analyzer HEWLETT PACKARD 8594E

NTSC Video Generator TEKTRONIX TSG100

3 2

3.3 TROUBLESHOOTING:

If the visual and/or aural output signals from the transmitter appear distorted, noisy or nonexistent,

consider the following procedure as a troubleshooting aid. This procedure assumes the transmitter

wiring as well as the cabling and connectors are trouble free. It also assumes the modulator is

receiving baseband video and audio signals while providing the required visual and aural IF

carriers at appropriate levels of 8dBm peak and 21dBm average, respectively. The general

problem area will be indicated by simply checking the front panel diagnostic lights as well as the

transmitter and Exciter RF POWER meters. The diagnostic indicators are located on the front

panel of the EMEX1 Exciter and on the Control/Metering panel at the top front of the transmitter

cabinet.

3.3a Control/Metering Panel Indicators:

1. Under normal operation the following indicators will be lit green:

AMPLIFIER

POWER SUPPLY

RF POWER meter = 100% with FWD green/<10% with REFL green

2. In standby operation the AMPLIFIER indicator will be lit green.

3. If the POWER SUPPLY indicator fails to illuminate with the transmitter in OPERATE, it is

signaling that one of the 32V power supplies in the 500W Power Amplifier drawer indicated

(A3PS1 or PS2 / see Figure 3 1) has failed and needs to be replaced. Until that time, the

IF/Converter’s output AGC circuit is deactivated allowing the transmitter to operate at

reduced power.

4. If the AMPLIFIER light goes out with the transmitter providing power, it indicates that one

of the output transistors in the 500W Power Amplifier drawer has failed. If a qualified

technician is available, the defective transistor can be replaced; otherwise, replace the

affected 300W Power Amplifier assembly (A3A1, A3A2) or 500W Power Amplifier drawer

(A3). In the interim, the fault indication has deactivated the IF/Converter’s output AGC

control so that the transmitter can operate at lower power.

5. If the AMPLIFIER TEMP indicator lights yellow, this is a sign that one of the 300W Amplifier

Assemblies in the 500W Amplifier drawer is operating at a temperature high enough to

cause transistor damage. This fault usually occurs due to high ambient temperature at the

transmission site, amplifier drawer cooling fan failure or lack of maintenance allowing for

fouled fans and blocked front panel air vents.

6. Assuming that the transmitter had previously been operating at its appropriate power and

none of the indicators discussed above are showing a fault, if the FWD RF POWER meter

is now reading less than 100% with the Exciter RF POWER meter indicating 100% (AGC

off) or more (AGC on), a loss of gain has occurred somewhere in the system after the

Exciter’s output. Check first for faulty cables or a detuned/defective output UHF Bandpass

Filter (A7FL1). Next, check the gain of the 500W Power Amplifier drawer. Neither the

Splitter (A3CP1), Combiner (A3CP2) nor driver amplifier transistors contained in the 500W

Power Amplifier are monitored and, if faulty, will cause loss of gain. Identify the problem

component and replace the affected drawer, amplifier assembly, module or component as

soon as possible. If it is necessary to operate the transmitter before repairs are effected,

be sure to defeat the output AGC by releasing (out) the Exciter’s AGC/MANUAL button.

3 3

7. If the REFL RF POWER meter registers more than 10% returned power, all the components

in the RF system (i.e., transmission line, antenna, jumpers) after the transmitter’s output

should be checked thoroughly for higher than normal VSWR. The offending component

should be repaired or replaced. If the output VSWR seen by the transmitter creates more

than 25% returned power, then the VSWR overload protection circuit will place the unit in

standby.

3.3b EMEX1 Exciter Drawer Indicators:

1. Under normal “on the air” operating conditions the Exciter’s green LED indicators should

appear as follows:

SYNTHESIZER LOCK on

IF STATUS on

AMPLIFIER STATUS on

LINEARITY CORRECTOR on

AGC ACTIVE on

SWEEP MODE off

OPERATE/STANDBY on

VSWR RESET off

AGC voltmeter 1 segment lit at approximate center

RF POWER meter 100%

2. An extinguished SYNTHESIZER LOCK light indicates that the UHF Synthesizer (A2A2) is

defective and should be replaced. Under this condition the transmitter is placed in

permanent standby until the problem is resolved.

3. The IF STATUS indicator provides verification that an IF signal of appropriate amplitude

and frequency is present at the Exciter’s input. Loss of IF input from the modulator will

cause this LED to shut off.

4. The AMPLIFIER STATUS indicator monitors the operation of the 2 Watt UHF Amplifier

module (A2A1) within the Exciter drawer. With the amplifier operating normally, the

indicator will be lit green. However, if one of the transistors within the module fails, this LED

will extinguish.

5. The LINEARITY CORRECTOR LED, when lit, indicates that the corrector is active. This

function is manually controlled by the ENABLE/BYPASS switch (A2PC2S1) mounted on the

corrector PC board. This indicator will turn off when the corrector switch is placed in

BYPASS.

6. The AGC ACTIVE light will be lit when the front panel AGC/MANUAL switch (A2PC3S2) is

pressed in engaging the transmitter’s output automatic gain control. With the front panel

switch placed in MANUAL (released/out), the AGC is disengaged and the LED will go out.

7. The SWEEP MODE LED will typically be turned off and is only active when the OPERATE/

SWEEP switch (A2PC4S1) on the Control/Interface board is placed in the SWEEP position.

This position deactivates both input and output AGC circuits so that low level sweep

measurements can be made.

3 4

8. The OPERATE/STANDBY indicator will illuminate with the associated front panel switch in

the OPERATE (depressed/in) position. The status of this indicator is fully dependent on the

position of the OPERATE/STANDBY switch (A2PC3S1) and will stay lit even if the trans-

mitter is forced into standby through some other means.

9. The VSWR RESET light will always be inactive until high reflected power appears at the

transmitter’s output causing a VSWR overload to occur. This indicator can be extinguished

by depressing the front panel momentary VSWR RESET switch, but only after the cause

of the high returned power has been cleared.

10. The AGC bar graph meter provides a gross indication of the output AGC voltage activity.

Normally, one of the two segments at the center of the meter will be lit suggesting that the

AGC system has been properly calibrated and that the transmitter is operating correctly.

With the AGC/MANUAL switch (A2PC3S2) in the AGC (in) position and a loss of gain in the

transmitter, the AGC circuit will see the reduction in output power and attempt to

compensate by increasing its voltage, thereby, adding more gain to the system. This action

will move the AGC meter indication toward the + or right side of the meter. If, for some

reason, the gain should increase in the transmitter amplifier chain, the AGC circuit will react

by decreasing its voltage, reducing system gain while, again, holding the transmitter’s output

constant. In this situation, the AGC meter bar indication will move toward the or left side

of the display.

11. The RF POWER meter (A2PC3DS9/10/11) provides an indication of the signal level

generated at the output of the Exciter. When driving higher power equipment (e.g.,

TTU500FA), this meter is calibrated for a 100% reading when the driven equipment is

operating at its rated power (100%).

3 5

3.3c TTU500FA Troubleshooting Chart:

The following chart is meant as an aid for uncovering faults that have developed in this transmitter.

During normal operation, all indicator LEDs are green, except the AMPLIFIER and VSWR OVLD

LEDs which are yellow and red, respectively, but are normally extinguished (in conjunction with the

SWEEP MODE light). This chart lists the LEDs that are indicating a fault by not appearing in their

normal state. If a problem develops with the transmitter, note the state of each indicator and

compare this to the chart below.

TTU500FA TROUBLESHOOTING CHART

PROBLEM INDICATORS CAUSE SOLUTION

NO OUTPUT

POWER ALL EXCITER DRAWER

INDICATORS UNLIT Exciter Power Supply

faulty Check 28V/15V/5V Power

Supply. Replace if

necessary.

SYNTH LOCK UNLIT

POWER SUPPLY UNLIT

RF POWER METER 0%

Defective Synthesizer Check synthesizer for

correct output level and

frequency. Replace if

necessary.

OPERATE UNLIT

POWER SUPPLY UNLIT

RF POWER METER 0%

Operate/Standby

switch in Standby Place switch (in) to

Operate.

Ground on A8J1-5 of

Remote plug Ensure transmitter has

not been placed in

standby through remote

system.

No video at input of

modulator Check video program

input and VDS tally.

VSWR RESET RED

RF POWER METER 0% VSWR overload Clear VSWR problem

and press Reset button.

IF STATUS UNLIT

RF POWER METER 0% No IF input from

modulator Fix cables or replace

modulator.

AMPLIFIER STATUS UNLIT

RF POWER METER 0% 2 Watt Amplifier faulty Replace module.

LOW OUTPUT

POWER AMPLIFIER TEMP YELLOW

POWER SUPPLY UNLIT

RF POWER <100%

High 300W Amplifier

temperature Insure site ambient

temperature is controlled.

Check fans for proper

operation and adequate

space to ventilate drawer.

TTU500FA TROUBLESHOOTING CHART

PROBLEM INDICATORS CAUSE SOLUTION

3 6

LOW OUTPUT

POWER AMPLIFIER UNLIT

RF POWER <100% Output transistor failure

in 300W Amplifier of

500W drawer indicated

Replace failed 500W

Amplifier drawer, 300W

Amplifier Assembly or

transistor.

POWER SUPPLY UNLIT

RF POWER <100% 32V Power Supply

failure in 500W drawer

indicated

Replace failed 500W

Amplifier drawer or 32V

power supply.

LOW OUTPUT

POWER OR

DISTORTED

OUTPUT

No Fault indicated Output Power

Calibration is incorrect See Section 3.5.

Modulator malfunction Replace modulator.

High loss in one of the

modules Test each module for

correct gain/loss. See

Signal Flow Diagram

(Fig 3 2) for gains/

losses.

Precorrector improperly

adjusted or not active See Section 3.6.

NO VISUAL

OUTPUT

(AURAL OK)

No Fault indicated Modulator failure Replace modulator.

Bad cable Check rear panel visual

loop-thru cable.

NO AURAL

OUTPUT

(VISUAL OK)

No Fault indicated Modulator failure Replace modulator.

Bad cable Check rear panel aural

loop-thru cable.

3 7

3.4 ALIGNMENT:

3.4a Exciter UHF Bandpass Filter:

1. With the transmitter operating normally, place the OPERATE/STANDBY switch to

STANDBY. Carefully pull out the Exciter drawer and remove its top cover. Leave the

Power Adjust control as it would be for normal operation and place the Control/Interface

board OPERATE/SWEEP switch (A2PC4S1) to the SWEEP position. (The front panel

SWEEP MODE light will turn on.)

2. Remove the modulator cable attached to the Exciter’s IF INput connector (J1). Also,

remove the RF cables attached to RF OUT connector (J3). Set up the test equipment as

shown in Figure 3 4. Set the VHF generator sweep width from 35 to 55MHz and use

45.75MHz and 41.25MHz markers if available.

3. Remove the four screws securing the UHF Bandpass Filter (A2FL1) to the Exciter chassis

and place the OPERATE/STANDBY switch to OPERATE. Adjust variable capacitors C1

through C6, accessible through the holes on the front side of filter assembly, to obtain the

frequency response shown in Figure 3 5. A small tuning tool is required for this procedure.

4. If the transmitter's channel is being changed to one that is more than 40MHz from the

factory preset, connect a spectrum analyzer to the 20dB attenuator in Figure 3 4 and find

the transmitter’s synthesizer/local oscillator (LO) frequency and the sweep signal appearing

on the low side of the LO. Tune the spectrum analyzer to the UHF Synthesizer's new

frequency as shown in Table 3 1, UHF Synthesizer Programming Chart. Program the

synthesizer for the new channel and look for the LO carrier on the analyzer. Tune the

analyzer 44MHz (36MHz for PAL B/G) below the LO frequency and tune capacitors C1

through C6 of the Bandpass Filter for maximum amplitude and bandwidth of the sweep

generator signal on the spectrum analyzer. Replace the analyzer with the diode detector

and oscilloscope, and adjust the Bandpass Filter for the response of Figure 3 5. In order

to obtain the appropriate bandwidth and loss characteristics (10dB minimum gain), it may

be necessary to open the filter and adjust the position of wire loading probes W1 through

W4. If possible, this procedure should be done using a network analyzer (or reasonable

substitute) to view input and output return loss, both of which should be less than 18dB.

IMPORTANT: If the transmitter’s output channel has been changed, the UHF

Bandpass Filter (A7FL1) at the unit’s output must be removed or replaced.

5. Once the filter is appropriately tuned, reattach the filter to the Exciter chassis, move the

Control/Interface OPERATE/SWEEP switch to the OPERATE position (SWEEP MODE LED

off), replace the cover on the Exciter drawer and remove the test equipment.

6. Recable the Exciter exactly as it was cabled when delivered and place the transmitter back

in operation according to Section 1.4 of this manual.

3.5 OUTPUT POWER CALIBRATION:

To ensure proper operation, the transmitter’s output power level and RF POWER meter calibration

should be checked once every year. With the meter switch in the FWD position, the RF POWER

3 8

meter has been factory calibrated for 100% with the transmitter providing 500 watts peak visual

and 25 watts average aural. The following calibration procedures assume that the composite signal

from the transmitter has the aural carrier 13dB down from the peak visual with the visual carrier

having 87.5% video modulation and 0% (sync only) average picture level (APL). The power levels

stated in the steps below are those expected at the output of the transmitter. Therefore, when

measuring these power levels using the equipment shown in Figure 3 6, be sure to take into

account the attenuation factor provided by the 20dB directional coupler and the 20dB attenuator.

Power levels at 50% APL (5 Step/Ramp/50% Flat Field) are included in brackets following the

power level at 0% APL.

3.5a Forward Power:

1. Assuming the transmitter is in operation, place the Exciter’s OPERATE/STANDBY switch

to STANDBY and set up the test equipment shown in Figure 3 6.

2. Using sync only video, verify that the modulator is providing 87.5% video modulation with

the aural carrier 13dB below the visual carrier. Release the Exciter AGC/MANUAL switch

to the MANUAL position and the transmitter RF POWER meter switch to FWD. Place the

Exciter OPERATE/STANDBY switch to OPERATE.

3. Wait for the transmitter to come up to power and, using a small tuning tool, rotate the

OUTPUT LEVEL ADJUST for an external power meter reading of 323W [195W]. Notice

that 500 watts of peak visual power at 0% [50%] APL plus 25 watts of average aural power

at 13dB down equals 323W [195W] power on the external average power meter.

4. To check and adjust visual to aural ratio, replace the power meter in Figure 3 6 with a

spectrum analyzer. Set the modulator’s aural carrier level adjustment for the desired visual/

aural ratio. Remove the spectrum analyzer, return the power meter to the transmitter output

and recheck power. Set the OUTPUT LEVEL ADJUST again for an external power meter

reading of 323W [195W].

5. With the external power meter reading correctly, place the Control/Metering panel meter

switch to FWD and check the transmitter's RF POWER meter for a 100% indication. If this

reading is not obtained, adjust FORWARD POWER potentiometer A5PC1R32, located

behind the Control/Metering panel (A5) and accessible through the METER ADJUST hole

marked FWD, for the correct indication.

6. Activate the transmitter’s output gain control by pushing in the Exciter AGC/MANUAL button

and recheck the power indication on the external meter for 323 watts [195W]. If the meter

reading is not correct, slowly turn the AGC LEVEL ADJUST (small tuning tool required) to

correct the transmitter output power. The output AGC circuit has a very long time constant

which requires the operator to wait for the transmitter power to settle after each small

movement of the AGC LEVEL ADJUST.

3 9

3.5b Reflected Power:

(OPTIONAL)

7. Carefully pull out the Exciter drawer and remove its top cover. On the Control/Interface

board find VSWR OVLD REF potentiometer A2PC4R12 and turn it fully counterclockwise

to disable the VSWR overload detection circuit. Place the Control/Metering panel RF

POWER meter switch to REFL.

8. Place the Exciter’s OPERATE/STANDBY switch to STANDBY and the AGC/MANUAL

switch to MANUAL. Switch the INCIDENT (J3) and REFLD (J4) coupling port cables on the

Output Section Metering Coupler (A7DC1). J2 (REFLD) of the Metering Detector (A7A1)

should now be connected to J3 (INCIDENT) of the Metering Coupler. This simulates an

open circuit at the transmitter's RF OUTput delivering maximum returned power to the

reflected power detector.

9. Place the OPERATE/STANDBY switch to OPERATE and wait until the external power

meter reading of 323 watts [195W] is reached. Check the front panel RF POWER meter

for a 100% reading. If the meter is incorrect, adjust it using REFLECTED POWER

potentiometer A5PC1R32 accessible through the METER ADJUST hole marked REFL on

the Control/Metering panel (A5).

10. Using the Exciter’s OUTPUT LEVEL ADJUST, decrease the transmitter's power to 25% as

seen on the RF POWER meter. This power level is used for setting the trip point of the

VSWR overload detection circuit. Return to the Exciter’s Control/Interface board and

slowly adjust VSWR OVLD REF potentiometer A2PC4R12 clockwise until the Exciter’s

VSWR RESET indicator illuminates red.

11. Check the VSWR OVLD trip point by pressing the momentary VSWR RESET switch on the

Exciter front panel which will reactivate the transmitter. As the transmitter power rises to

25%, the VSWR overload circuit should again trip. If it does not, carefully rotate the VSWR

OVLD REF adjust further clockwise and repeat this step to recheck the trip point.

12. Place the OPERATE/STANDBY switch to STANDBY and return the metering cables to their

original coupler ports (DC1J3/J4). Remove all test equipment from the transmitter, replace

the top cover on the Exciter and push the drawer back into the rack.

13. After properly loading the transmitter, place the unit in operation by pressing the OPERATE/

STANDBY switch in and resetting the OUTPUT LEVEL ADJUST for a 100% indication on

the RF POWER bar graph meter. Reactivate the transmitter’s output AGC as explained in

step #6 above.

3.6 LINEARITY CORRECTOR ADJUSTMENT:

Adjustment of the transmitter linearity is accomplished using eight potentiometers on the Exciter

Linearity Corrector board (A2PC2). Since the Linearity Corrector can produce unwanted distortion

if adjusted incorrectly, this circuit should not be realigned unless absolutely necessary. The test

equipment which should be available for readjustment of the precorrector is a spectrum analyzer

which provides demodulated video for measurement of sync and intermodulation and/or a video

measurement set with television demodulator for sync, differential gain, differential phase and

ICPM measurements. Acquire as much of this test equipment as possible since the precorrection

accuracy will depend on equipment versatility. It is assumed that all the transmitter's circuits are

310

operating properly and its frequency response is correct (Section 3.4a), allowing the unit to operate

with maximum efficiency.

1. Place the transmitter in standby and connect the test equipment available for monitoring

intermodulation, sync amplitude and differential gain and phase.

2. Remove the top cover of the Exciter drawer and insure that the Linearity Corrector

BYPASS/ENABLE switch (A2PC2S1) is in the ENABLE position causing the front panel

LINEARITY CORRECTOR light to illuminate.

3. Place the transmitter in operation with the system providing its rated output power. After

demodulating video, find the distortion that needs the most correction and slowly adjust the

potentiometers shown on the table below dedicated to that type of distortion. Those

adjustments designated as CUT IN are used to position the correction on a specific part of

the waveform being modified. Those adjustments specified as SLOPE increase and

decrease the amount of correction applied. Remember that the corrector was factory

calibrated and should need very little readjustment. Also, be aware that, while manipulating

the corrector, the transmitter’s output must be carefully monitored since changes in linearity

can significantly alter the unit’s output power.

ADJUSTMENT CORRECTION FUNCTION

R21 Diff. Phase Cut In

R15 Diff. Phase Slope

R30 Diff. Phase Cut In

R25 Diff. Phase Slope

R47 Diff. Gain Cut In

R41 Diff. Gain Slope

R55 Sync Cut In

R57 Sync Slope

4. After the adjustments in step #3 are completed, modulate the visual signal with a modulated

ramp waveform and place the transmitter signal on a spectrum analyzer (100kHz resolution

bandwidth) to view in-band intermodulation distortion. Carefully readjust R21 and R15 to

null the IM3 distortion products.

5. Check and, if necessary, readjust the transmitter's output power using the Exciter’s Control/

Interface AMPLIFIER GAIN ADJUST (A2PC4R7).

6. Repeat steps #3 and #4 to find the appropriate trade-off between differential phase,

differential gain, sync amplitude and intermodulation distortion.

7. Place the transmitter in standby, remove the test equipment, reinstall the top cover on the

Exciter and slide the drawer back into the cabinet. Properly load the transmitter’s output

and place it back on the air.

311

3.7 REMOTE MONITOR SIGNAL LEVELS:

This table lists the signals necessary for control and monitoring of the transmitter provided on the

REMOTE connector (A8J1) located on the rear Video/Audio/Remote panel.

NAME PIN I/O TTL TYPICAL LEVEL

REFL POWER 1 O <+1V

AGC VOLTAGE 2 O <+7.5V

FWD POWER 3 O +3V

OPERATE/STANDBY 5 I X Open/Gnd

VSWR RESET 6 I X Gnd

AGC ON/OFF 7 I X Open/Gnd

GND 8 I/O Gnd

S 1

3.8 SPARE MODULES AND COMPONENTS:

The following contains the description, vendor, part number, and designator of each module found

in the TTU500FA Transmitter which EMCEE considers to be essential bench-stock items. One

each of these items should be available to the technician at all times.

TTU500FA

INTERCONNECTION DIAGRAM 40400003

DESCRIPTION VENDOR/PART # DESIGNATOR

Fans 10" / 560CFM / 220Vac EMCEE/4C829 B1, B2

Control/Monitor Board EMCEE/30400047-2 A5PC1

500W UHF POWER AMPLIFIER

INTERCONNECTION DIAGRAM 30394008

DESCRIPTION VENDOR/PART # DESIGNATOR

Fans 6" / 230CFM / 220Vac COMAIR/031844 A3B1, A3B2

300W UHF Power Amplifier Assy. EMCEE/40394177-2 A3A1, A3A2

32V Power Supply VICOR/PM1-02-520PFC A3PS1, A3PS2

S 2

EMEX1 UHF EXCITER

INTERCONNECTION DIAGRAM 40404001

DESCRIPTION VENDOR/PART # DESIGNATOR

Linearity Corrector EMCEE/20404013-1 A2PC2

IF/Converter EMCEE/20404023-1 A2PC1

2 Watt UHF Amplifier EMCEE/40404059-1 A2A1

UHF Synthesizer EMCEE/60367103-1 A2A2A1

Reference Oscillator EMCEE/60368055-1 A2A2A2

Metering Detector EMCEE/40400053-1 A2A3

28V/15V/5V Power Supply IPD/SWR-65-4006-28 A2PS1

Control/Interface Board EMCEE/30404038-1 A2PC4

Display/Monitor Board EMCEE/30404043-1 A2PC3

Fan 2.5" / 20CFM / 24Vac NMB/2410ML-05W-B30-P00 A2B1

Table 3 1

Page 1 of 2

3.9 SYNTHESIZER PROGRAMMING:

UHF SYNTHESIZER PROGRAMMING CHART (NTSC)

Channel Visual Frequency

(MHz) LO Freq

(MHz) S4 S3 S2 S1

14 471.25 517 0 A 1 9

15 477.25 523 0 A 3 7

16 483.25 529 0 A 5 5

17 489.25 535 0 A 7 3

18 495.25 541 0 A 9 1

19 501.25 547 0 A A F

20 507.25 553 0 A C D

21 513.25 559 0 A E B

22 519.25 565 0 B 0 9

23 525.25 571 0 B 2 7

24 531.25 577 0 B 4 5

25 537.25 583 0 B 6 3

26 543.25 589 0 B 8 1

27 549.25 595 0 B 9 F

28 555.25 601 0 B B D

29 561.25 607 0 B D B

30 567.25 613 0 B F 9

31 573.25 619 0 C 1 7

32 579.25 625 0 C 3 5

33 585.25 631 0 C 5 3

34 591.25 637 0 C 7 1

35 597.25 643 0 C 8 F

36 603.25 649 0 C A D

37 609.25 655 0 C C B

38 615.25 661 0 C E 9

39 621.25 667 0 D 0 7

40 627.25 673 0 D 2 5

41 633.25 679 0 D 4 3

42 639.25 685 0 D 6 1

UHF SYNTHESIZER PROGRAMMING CHART (NTSC)

Channel Visual Frequency

(MHz) LO Freq

(MHz) S4 S3 S2 S1

Table 3 1

Page 2 of 2

43 645.25 691 0 D 7 F

44 651.25 697 0 D 9 D

45 657.25 703 0 D B B

46 663.25 709 0 D D 9

47 669.25 715 0 D F 7

48 675.25 721 0 E 1 5

49 681.25 727 0 E 3 3

50 687.25 733 0 E 5 1

51 693.25 739 0 E 6 F

52 699.25 745 0 E 8 D

53 705.25 751 0 E A B

54 711.25 757 0 E C 9

55 717.25 763 0 E E 7

56 723.25 769 0 F 0 5

57 729.25 775 0 F 2 3

58 735.25 781 0 F 4 1

59 741.25 787 0 F 5 F

60 747.25 793 0 F 7 D

61 753.25 799 0 F 9 B

62 759.25 805 0 F B 9

63 765.25 811 0 F D 7

64 771.25 817 0 F F 5

65 777.25 823 1 0 1 3

66 783.25 829 1 0 3 1

67 789.25 835 1 0 4 F

68 795.25 841 1 0 6 D

69 801.25 847 1 0 8 B

For PAL operation the grounds to Pins 21 and 23 of U1 (MC145152) must be removed.

Table 3 1

Page 1 of 2

UHF SYNTHESIZER PROGRAMMING CHART (PAL)

Channel Visual Frequency

(MHz) LO Freq

(MHz) S4 S3 S2 S1

21 471.25 510.15 0 9 F 6

22 479.25 518.15 0 A 1 E

23 487.25 526.15 0 A 4 6

24 495.25 534.15 0 A 6 E

25 503.25 542.15 0 A 9 6

26 511.25 550.15 0 A B E

27 519.25 558.15 0 A E 6

28 527.25 566.15 0 B 0 E

29 535.25 574.15 0 B 3 6

30 543.25 582.15 0 B 5 E

31 551.25 590.15 0 B 8 6

32 559.25 598.15 0 B A E

33 567.25 606.15 0 B D 6

34 575.25 614.15 0 B F E

35 583.25 622.15 0 C 2 6

36 591.25 630.15 0 C 4 E

37 599.25 638.15 0 C 7 6

38 607.25 646.15 0 C 9 E

39 615.25 654.15 0 C C 6

40 623.25 662.15 0 C E E

41 631.25 670.15 0 D 1 6

42 639.25 678.15 0 D 3 E

43 647.25 686.15 0 D 6 6

44 655.25 694.15 0 D 8 E

45 663.25 702.15 0 D B 6

46 671.25 710.15 0 D D E

47 679.25 718.15 0 E 0 6

48 687.25 726.15 0 E 2 E

49 695.25 734.15 0 E 5 6

UHF SYNTHESIZER PROGRAMMING CHART (PAL)

Channel Visual Frequency

(MHz) LO Freq

(MHz) S4 S3 S2 S1

For PAL operation the grounds to Pins 21 and 23 of U1 (MC145152) must be removed.

Table 3 1

Page 2 of 2

50 703.25 742.15 0 E 7 E

51 711.25 750.15 0 E A 6

52 719.25 758.15 0 E C E

53 727.25 766.15 0 E F 6

54 735.25 774.15 0 F 1 E

55 743.25 782.15 0 F 4 6

56 751.25 790.15 0 F 6 E

57 759.25 798.15 0 F 9 6

58 767.25 806.15 0 F B E

59 775.25 814.15 0 F E 6

60 783.25 822.15 1 0 0 E

61 791.25 830.15 1 0 3 6

62 799.25 838.15 1 0 5 E

63 807.25 846.15 1 0 8 6

64 815.25 854.15 1 0 A E

65 823.25 862.15 1 0 D 6

66 831.25 870.15 1 0 F E

67 839.25 878.15 1 1 2 6

68 847.25 886.15 1 1 4 E

EMCEE Broadcast TTU500FA UHF LPTV Transmitter User Manual TTU1000FA Mnl Cover Pg 1

EMCEE Broadcast Products UHF LPTV Transmitter TTU1000FA Mnl Cover Pg 1

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