Telephonics MCB-RT-1601 Color Weather and Search and Rescue Radar User Manual maintenance manual

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Document ID	271074
Application ID	w0JsFzVvATRduzlqu4qxiA==
Document Description	maintenance manual
Short Term Confidential	No
Permanent Confidential	No
Supercede	No
Document Type	User Manual
Display Format	Microsoft Word - pdf
Filesize	59.76kB (747009 bits)
Date Submitted	2002-09-18 00:00:00
Date Available	2002-10-04 00:00:00
Creation Date	2002-09-18 11:19:05
Producing Software	Acrobat Distiller 4.0 for Windows
Document Lastmod	2002-09-18 11:19:07
Document Title	maintenance manual

MAINTENANCE MANUAL
RT-1601 RECEIVER-TRANSMITTER
SECTION 1 DESCRIPTION AND OPERATION
1. General
This section provides a general description of the circuit functions and operation of the RT-1601 Receiver-Transmitter.
Subsequent information includes operation, equipment part numbers, block diagram discussion, and theory of operation.
NOTE: General information for the RDR-1600 Weather Radar System, such as system leading particulars, system
operation, and a system operational check is contained in the Radar System Installation Manual, TM106601 Maintenance
information for the DA-1203A Radar Antenna is contained in PART 1 of the Weather vision System Antennas
Maintenance Manual, I.B. 21000A.
2. Operation
The receiver-transmitter (R-T) operates by emitting very short, intense pulses of microwave energy, which are
reflected within the range of the radar system. A portion of the radiated energy, reflected by an object having
reflective characteristics, is returned along the same general path to the aircraft where it is received and
converted into digital data that is representative of the target size. The digital data is then routed to the radar
indicator where it is processed to give a visual presentation of the target.
The receiver-transmitter is housed in a short ½ ATR form factor case. Overall dimensions can be found on the
receiver–transmitter outline drawing. The mounting tray for the R-T unit, which is designed for front loading,
provides positive positioning and holding of the unit to the aircraft. The mounting tray is mounted to the aircraft,
and the R-T unit can easily be removed and replaced for servicing. Depending upon installation requirements,
different models of the mounting tray are available.
For ease of maintenance, all circuits are contained on plug-in boards. These PC boards are interconnected by
way of a ribbon cable, which makes all connections between PC boards. An interconnect PC board replaces
the conventional wiring harness arrangement.
The RT-1601 uses a frequency trimmable magnetron for reliable interrogation of beacon transponders; input
frequency in an accurate 9375 +5 MHz.
The RT-1601 functions as short-range pulse radar for high resolution ground mapping (search) and a long range
pulse for conventional weather. The reflected signal is received by the system’s sector scanning antenna,
amplified and digitized by the R-T unit, and then routed to the radar indicator. All system power requirements
are routed via the R-T unit to the radar indicator and the antenna.
3. Equipment Part Numbers
Table 1 lists the TELEPHONICS part number for the RT-1601 Receiver-Transmitter. A brief description
of the unit is also provided. Table 2 lists the major assemblies in the RT-1601
815 Broadhollow Road
Farmingdale, N.Y. 11735
631-755-7000
FAX 631- 755-7200
MAINTENANCE MANUAL
RT-1601 RECEIVER-TRANSMITTER
TELEPHONICS
PART NUMBER
379-2011-001
TYPE
DESCRIPTION
RT-1601
Provides X-band output to sector-scanning antenna. Reflected signal is amplified by
receiver, digitized, and routed to the radar indicator. The magnetron is frequency
trimmable and is designed to operate at 9375 +5 MHz to permit reliable triggering of the
beacon transponder. Operating parameters permit optimum performance in each of the
five modes (3 search modes, weather mode, and beacon mode) complies with TSO
certification C102 for ground target approach to within 1000 feet.
Table 1. RT-1601 Receiver-Transmitter Part Numbe rs
MODULE OR
ASSEMBLY NAME
Interconnect (Mother) Board
Front Panel Connector Board
Receiver Board
Mode-Decode Board
Power Supply Assembly
PS Control Board Assembly
Power Supply Module
Local Oscillator Assembly
Beacon Amplifier Assembly
Beacon Receiver Module
PART NUMBER
REFERENCE
SERIES
1200
3606464-0501
3606464-0502
3606465-0501
3606458-0501
379-2040-001
4007721-0504
4007714-0501
4007715-0501
4007932-0501
3606473-0501
1100
2000
8000
5000
5000
5000
6000
7000
CONNECTORS
J1204, J1205, J1208, J1217, J1218
P1101, P1103
J2006, J2016, P2020, P2021
J8023
J5011
P6012
P7016, P7019
Table 2:RT-1601 Subassemblies and Connectors
4. Block Diagram Discussion
(Refer to figure 1)
A. Waveform Synchronization and Transmitter Function
A crystal-controlled oscillator located in theMode Decode board generates basic synchronization
signals for the radar system. The clock frequency is counted down to 1536 Hz for range selections
of 10 NM or less in search-one and search-two modes. For all other ranges and modes the clock
frequency is counted down to 200 Hz. Either the 1536 Hz or the 200 Hz system trigger keys the
transmitter and provides other timing functions. The system trigger also keys the suppression pulse
generator to turn off sensitive equipment when the R-T unit transmits. The System trigger is applied
to the timing circuit, which controls the AFC gate, the STC-function gate, the AFC-AGC trigger, and
the test-pattern-generator circuits. The system trigger is buffered and routed to the modulator driver
815 Broadhollow Road
Farmingdale, N.Y. 11735
631-755-7000
FAX 631- 755-7200
MAINTENANCE MANUAL
RT-1601 RECEIVER-TRANSMITTER
where selection of either the modulator short pulse (0.2 usec) or the modulator long pulse (2.35
usec) is selected.
Pulse width selection is made depending on the operation mode selected on the radar indicator.
Modulator long pulse is selected for modes using a 200-Hz trigger; modulator short pulse is
selected for modes using an 1536 Hz trigger. With either modulator pulse, a negative-going, 330volt, 110-ampere pulse is applied to the pulse transformer. The pulse transformer supplies the
magnetron with a 5.5 kV, 4.5 A, negative-going pulse that causes the magnetron to oscillate at its
9375 MHz resonant frequency. A 10-kW nominal peak power RF output pulse is generated by the
magnetron and is directed through the four-port, E-plane circulator to the radar antenna.
B. Receiver Function
The R-T unit employs a dual-conversion, superheterodyne receiver. Signals received by the radar
antenna are routed through the four-port, E-plane circulator, and the TR limiter to a alanced mixer.
A TR limiter is a microwave switch used to prevent
damage to the receiver crystals, from the
magnetron oscillator high power microwave pulses or from other radars in the vicinity. The
balanced mixer combines the echo signal with a signal from the first local oscillator (operating at
9401.3 MHz) to produce a difference frequency of 26.3-MHz. After amplification in the preamplifier
stage, the 26.3-MHz signal is mixed with a 36.6-MHz signal from the second local oscillator to
produce a 10.3-MHz I-f signal.
A bandwidth switch selects either a 2-MHz bandwidth for search-mode operation or a 0.5-MHz
bandwidth for weather-mode operation. The 10.3-MHz logarithmic-gain amplifier following the
bandwidth switch provides for a great variance (approximately 50 dB) in signal levels usable by the
R-T unit. Following the logarithmic-gain amplifier, is the video detector and buffer. The detected,
buffered video (in the search 1 mode) is acted upon by the FTC circuit (fast time constant) and it is
used to remove noise caused by the sea clutter. In the A/D converter following the FTC circuit the
amplitude of the detected video signal is compared to three preset dc thresholds. A two-bit logic
code tells the radar indicator the highest threshold level exceeded by the echo return. The two-bit
codes for the four thresholds, in increasing level, are 00, 01, 11, and 10.
C. AFC Function
After the system trigger, while the magnetron is oscillating, the first local oscillator frequency must
be adjusted to ensure a correct i-f echo-return signal. The AFC-AGC trigger circuit turns on the
AFC gate, and the I-f signal from the preamplifier is supplied to the AFC mixer. Using the 36.6MHz signal from the second local oscillator, the mixer converts the 26.3-MHz I-f signal to a 10.3
MHz second I-f. The discriminator following the 10.3-MHz buffer checks the I-f frequency. If the
second I-f is exactly 10.3-MHz the AFC circuits remain stabilized. However, if the second I-f is not
exactly 10.3 MHz, the discriminator produces a deviation voltage. The deviation voltage is
amplified, integrated, buffered, and applied to the varactor in the first local oscillator to adjust the
local oscillator frequency. An inverse-logarithmic-gain buffer amplifier is used between the
integrator and the first local oscillator to cancel the logarithmic voltage-to-frequency characteristic of
815 Broadhollow Road
Farmingdale, N.Y. 11735
631-755-7000
FAX 631- 755-7200
MAINTENANCE MANUAL
RT-1601 RECEIVER-TRANSMITTER
the first local oscillator. If the first local oscillator is not very nearly 26.3 MHz above the magnetron
frequency when the magnetron fires, the 10.3-MHz second AFC I-f will be outside the discriminator
capture range. In this case the stop-sweep, or reset, circuit will initiate integrator reset and AFC
sweep. To ensure that the first local oscillator does not lock on the difference frequency 26.3 MHz
below the magentron frequency, the AFC sweep circuit causes the first local oscillator to start at its
highest frequency and sweep down. If the first local oscillator does not lock up during the downsweep, the integrator is reset when the time voltage reaches zero volts and the sweep begins again.
D. AGC Function (Wx AGC and BCN AGC)
The AGC circuit in the RT-1601 is noise –level actuated. Gain of the preamplifier circuits is
adjusted in response to the noise level received by the AGC threshold circuit from the videodetector buffer. Video detector output must not be monitored immediately after the transmitted
radar pulse, however, as the returning echo signal would simulate a high noise level. The AFCAGC trigger circuit prevents the false reading by shutting off the AGC threshold circuit during the
echo-return time. In beacon, weather, or search-three operating modes (when the pulse repetition
rate is 200 Hz), the AGC-AFC trigger turns off the AGC threshold circuit for about three milliseconds
after the magnetron fires. This is long enough to allow the echo to return, but still leaves time for
the AGC threshold circuit to be turned on for noise-level sampling before the next magnetron firing.
To prevent any return after 0.7 milliseconds from affecting the AGC noise-level sampling, the AFCAGC trigger circuit turns on the AFC side-step circuit. This causes the firs local oscillator to be
driven off-frequency. Therefore, any echo return after 0.7 millisecond in search-one or search-two
modes is ignored. The AFC side-step is also used as a 3000 microsecond gate.
E. STC (Sensitivity Time Control) Function
The STC function generator is initiated after the transmitter output pulse. The generator causes the
gain of the 26.3-MHz preamplifier to increase exponentially. The weaker returns from distant
objects are thus amplified more than the strong returns from nearer objects. Thus, objects of the
same size or density are made to look equal on the radar indicator, regardless of their distance.
F. Test Function
When the system is placed in the test mode, a test ground generated by the radar indicator inhibits
the transmitter and keys a test pattern generator. The triangular wave developed by the test pattern
generator is injected into the video-detector buffer. A resultant test pattern display on the radar
indicator is indicative of system performance. The test pattern exhibits three colors, in five bands.
G. Beacon Amplifier
When operating in beacon mode, or dual mode (e.g., weather plus beacon), the R-T unit must
transmit the standard 9375-MHz signal and receive the 9310-MHz transponder signal. To process
the 9310-MHz signal, a separate beacon I-f amplifier (91.3 MHz) and beacon video detector are
815 Broadhollow Road
Farmingdale, N.Y. 11735
631-755-7000
FAX 631- 755-7200
MAINTENANCE MANUAL
RT-1601 RECEIVER-TRANSMITTER
used. The R-T unit first local oscillator operates at 9401.3-MHz to convert the standard 9375-MHz
signal to a 26.3-MHz intermediate frequency. The same first local oscillator converts the 9310-MHz
transponder signal to 91.3 MHz. The 91.3-MHz signal is amplified by the preamplifier and the 91.3MHz I-f amplifier, detected, and then applied to the video-detector buffer.
5. Detailed Theory of Operation
A. Power Supply
(1) General (See figure 1.)
The power supply for the R-T unit converts +28 Vdc into the dc voltages needed for unit
operation: +23V, +6V, +15V, -20.5V and –330V. Two series transistors mounted on the
main frame are driven by the power supply circuits to provide regulated -23 Vdc. An
overload circuit in power supply limits current. Since +28 Vdc is continuously applied to the
R-T unit, a power supply on-off switch circuit is used to control R-T unit operation in
response to demands from the radar indicator. All voltages except the +23 Vdc are
developed by chopping the +23 Vdc, then transforming, rectifying, and filtering the chopped
voltage. The high voltage control and overload circuit, in addition to protecting the high
voltage ac-dc converter from overload, provides the trigger enable signal. Trigger enable is
generated after a 80-second, turn-on delay from the time-delay circuit, and is used to
switch-on –330 Vdc to the magnetron modulator as well as to enable the modulator trigger
on the mode decoder board. A fan is provided for cooling the power supply.
Figure 1 POWER SUPPLY BLOCK DIAGRAM
815 Broadhollow Road
Farmingdale, N.Y. 11735
631-755-7000
FAX 631- 755-7200
MAINTENANCE MANUAL
RT-1601 RECEIVER-TRANSMITTER
BEACON RECEIVER
Transmitter
To
Antenna
STC
MAGNETRON
9375Mhz
+/- 5Mhz
Pulse
LONG PULSE
MODULATOR
91.3Mhz
Log
AMP
Vid-Detec
Gain Adj
STC
Pulse
91.3Mhz
10.3Mhz
10.3Mhz
T-R
Limitter
Pre
AMP
SHORT PULSE
MODULATOR
Log
AMP
BW
Control
Mixer
Log
AMP
Vid-Detec
Test Pulse
STC
WX Receiver
FTC
Switch
BCN en
36.6Mhz
9375Mhz
AFC Sweep
26.3Mhz
MIXER
36.6Mhz
2nd L.O
9401.3Mhz
AFC
Discriminator
Data Comparator
BW
Control
VCO
1st L.O
Sys
Trigger
AGC Gate
Analog Video
Data bits
PRF
Generator
STC
Generator
Power
Supply
Mode Set
NC-104
FUNCTIONS
Mode Control and Timing
GEN
System Trigger
Gain
Control
Fault
Monitor
Test Func
Generator
Mode Set
Figure 2 RT-1601 BLOCK DIAGRAM
815 Broadhollow Road
Farmingdale, N.Y. 11735
631-755-7000
FAX 631- 755-7200
Mode Decode
453 Data
to display
429 Data

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Create Date                     : 2002:09:18 11:19:05
Producer                        : Acrobat Distiller 4.0 for Windows
Modify Date                     : 2002:09:18 11:19:07-04:00
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