Ritron RIT13-450 UHF-FM Handheld Radio Transceiver User Manual SST 454 THEORY OF OPERATION
Ritron Inc UHF-FM Handheld Radio Transceiver SST 454 THEORY OF OPERATION
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Maintenance manual
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TYPE OF EXHIBIT: INSTRUCTION MANUALS
FCC PART: 2.1033 (c)(3)
MANUFACTURER: RITRON, INC.
505 West Carmel Drive
Carmel, IN 46032
MODEL: SST-444
TYPE OF UNIT: UHF-FM Handheld Transceiver
FCC ID: AIERIT13-450
DATE: July 7, 2000
Included in this exhibit is a draft of the Maintenance and Operating Manual for RITRON Model Patriot
SST-444 UHF-FM Handheld Transceiver.
Specifically, this manual includes a technical description of the SST-444 sufficient to establish compliance
with the technical standards of the applicable rule part(s).
This includes, but is not limited to, the following items required under FCC Part 2.1033 (c):
(2) FCC Identifier.
(3) A copy of the installation and operating instructions.
(4) Type of emission.
(5) Frequency range.
(6) Range of operating power, and means to provide variation in operating power.
(7) Maximum power rating.
(8) DC voltage chart.
(9) Tune-up procedure.
(10) A description of all frequency determining and stabilization circuits. A description of the circuits
used to suppress spurious radiation, limiting modulation, and limiting power.
(12) Drawing with labels for controls and complete circuit diagrams.
Signed: Michael A. Pickard - Project Engineer
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TABLE OF CONTENTS
SECTION TOPIC PAGE
1. SST-444 SPECIFICATIONS
GENERAL 4
RECEIVER 5
TRANSMITTER 6
2. INTRODUCTION
GENERAL 7
Inspection 7
Model Identification 7
FCC REGULATIONS
Licensing 7
Safety Standards 7
3. BATTERY CARE
CHARGING 8
BATTERY REPLACEMENT 9
PRECAUTIONS 9
4. DESCRIPTION OF CONTROLS AND CONNECTORS 10
Fig. 2 Controls and Connectors 11
Belt Clip Installation 11
5. OPERATION
On-Off/Volume 12
Receive 12
Monitor 12
Selective Signaling Squelch 12
Battery Saver 12
Transmit 13
Channel Selection 13
WHAT THE RADIO TONES MEAN
Power On/Self Check “OK 13
Error Tones 13
Channel Select 13
Tone Squelch 13
Recharge Battery Alert 13
OPTIONAL RADIO TONES
Receiver Squelch Tone 14
Busy Channel Inhibit 14
Transmitter Time Out 14
TROUBLESHOOTING
General 15
Battery 15
Error Tones 15
Tone Coded Squelch 16
6. PROGRAMMING THE RADIO
PTT (PUSH-TO-TALK) PROGRAMMING
Placing the Radio in PTT Programming Mode 17
How To Find Out What Is Already Programmed 17
PTT Programming the Radio 18
PTT Programming Mistakes 18
Return To Normal Operation 18
Table 1 – PTT Programming Frequency Table 19
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Table 2 – Quiet Call Codes and Frequencies 19
COMPUTER SOFTWARE COPYRIGHTS 19
PROGRAMMING THE RADIO USING A PC COMPUTER 20
Programmable Features 20
Description of Features 21
7. SST-444 THEORY OF OPERATION
INTRODUCTION 22
POWER SUPPLY AND VOLTAGE DISTRIBUTION 22
Power Strobe 22
Low Battery Voltage Detection 22
REFERENCE OSCILLATOR 23
SYNTHESIZER 23
Pin Numbers 23
Prescaler Divider / Synthesizer Controller 23
VCO / Buffer Amplifiers 24
Oscillator Modulation 24
DIGITAL POTENTIOMETERS 24
RECEIVER 25
RF Amplifier 25
1st Mixer 25
FM Receiver Subsystem 25
Voice / Tone Conditioning in Receiver Mode 25
Voice Band 26
Sub-Audible 26
Audio Amplifier 26
ANTENNA SWITCHING / LOW-PASS FILTER 26
TRANSMITTER 27
Keying 27
+VTX Supply 27
Power Amplifier 27
Voice/Tone Conditioning in Transmit Mode 27
Voice Band 27
Sub-Audible 28
MICROCONTROLLER 28
8. SST-444 ALIGNMENT PROCEDURE
RECOMMENDED TEST EQUIPMENT 30
RADIO PREPARATION 30
REFERENCE FREQUENCY 31
MODULATION BALANCE 31
TRANSMITTER TONE DEVIATION 31
TRANSMITTER VOICE DEVIATION 32
TRANSMITTER POWER 32
RECEIVER SENSITIVITY AND SQUELCH 32
RECEIVER NOISE SQUELCH 33
SYNTHESIZER 33
9. SST-444 VOLTAGE CHART
Measurement Conditions 34
SST-444 Voltages 34
10. SST-444 SCHEMATIC REFERENCE PARTS LIST 40
11. SST-444 CASE ASSEMBLY PARTS LIST 47
12. SCHEMATIC AND PART PLACEMENT DRAWINGS 48
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IMPORTANT MAINTENANCE/REPAIR INFORMATION
Surface Mount Repair
RITRON surface mount products require special equipment and servicing techniques. Improper servicing
techniques can cause permanent damage to the printed circuit boards and/or components, which is not
covered by RITRON’s warranty. If you are not completely familiar with surface mounted component repair
techniques, RITRON recommends that you defer maintenance to qualified service personnel.
Precautions for Handling CMOS Devices
This radio contains complementary metal-oxide semiconductor (CMOS) devices, which require special
handling techniques. CMOS circuits are susceptible to damage by electrostatic or high voltage charges.
Damage can be latent, with no failure appearing until weeks or months later. For this reason, take special
precautions any time you disassemble the radio. Follow the precautions below, which are even more
critical in low humidity environments.
1) Storage/transport - CMOS devices that will be stored or transported must be placed in conductive
material so that all exposed leads are shorted together. CMOS devices must not be inserted into
conventional plastic “snow” or plastic trays of the type that are used for other semiconductors.
2) Grounding - All CMOS devices must be placed on a grounded bench surface. The technician that will
work on the radio/CMOS circuit must be grounded before handling the radio. Normally, the technician
wears a conductive wrist strap in series with a 100K Ohm resistor to ground.
3) Clothing - Do not wear nylon clothing while handling CMOS circuits.
4) Power off - Remove power before connecting, removing or soldering a PC board that contains CMOS
devices.
5) Power/voltage transients - Do not insert or remove CMOS devices with power applied. Check all
power supplies to be used for testing CMOS devices, making sure that no voltage transients are
present.
6) Soldering - Use a grounded soldering iron for soldering CMOS circuitry.
7) Lead-straightening tools - When straightening CMOS leads, provide ground straps for the tool used.
PC Board Removal - Special Tool
RITRON recommends using a knurled nut tool to remove the slotted knurled nuts that secure the charge
and audio jacks on top of the radio. You will need two sizes of this tool, one for each jack size. Mouser
Corporation is one source, stock number 382-0004 (2.5mm jack) and 382-0006 (3.5mm jack). You can
reach Mouser sales and distribution center at 1-800-346-6873.
Properly Attach the Synthesizer Shield
The synthesizer shield should not be removed, unless a component must be replaced. This shield is
soldered to the main PC board.
Re-assembly - Speaker Magnet, Battery Voltage on Connector Pin
The speaker magnet will pick up clipped leads and other small metal objects from your bench top. Even
tiny objects on the diaphragm will cause the speaker to buzz. Make sure the speaker is free of foreign
objects before reassembling the radio.
Radio Transmitter Power Measurements
The SST-444 was designed to produce a minimum of 3.5 Watts of Transmitter power at nominal battery
voltage (+7.2 VDC), throughout the radio’s operating frequency range. Measurements are made with the
RITRON SST-SRVBD RF service module connected to the radio antenna terminal. The transmitter was
designed with close tolerances to prevent RF power output from exceeding specifications and reducing
battery life.
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SST-444 SPECIFICATIONS
GENERAL
FCC ID: AIERIT13-450
FCC Rule Parts: 22, 74, 80, 90
Frequency Range: 460 to 470 MHz standard
Max. Freq. Separation: 10 MHz
RF Channels: Conventional: 4 Channels, Independent TX/RX frequencies.
Synthesizer Step Size: 12.5 KHz
Frequency Stability: +/-2.5 PPM (-30 to +60 C) TX/RX
Tone/Code Signaling: CTCSS (Quiet Call)
Digital Coded Squelch (Digital Quiet Call)
Power Supply: +7.5 VDC, 800 mAH rechargeable NiCd battery pack standard
+7.5 VDC, 1500 mAH rechargeable MiMH battery pack optional
Battery Drain:
Standby: 52 mA
Sleep: 12 mA
Avg. Standby with Power Saver: 24 mA
Receive: 125 mA
Transmit: 1500 mA @ 4 Watts
500 mA @ 1 Watt
Battery Life:Standard battery (800 mAH) @ 90/5/5 Duty Cycle
8.2 Hrs, Battery Saver On, TX High Power
16.8 Hrs, Battery Saver On, TX Low Power
6.2 Hrs, Battery Saver Off, TX High Power
10.2 Hrs, Battery Saver Off, TX Low Power
High capacity battery (1500 mAH) @ 90/5/5 Duty Cycle
13.3 Hrs, Battery Saver On, TX High Power
27.3 Hrs, Battery Saver On, TX Low Power
10.2 Hrs, Battery Saver Off, TX High Power
16.7 Hrs, Battery Saver Off, TX Low Power
Dimensions: 4.75”H x 2.2”W x 1.43”D
Weight: 11.5 oz. with battery pack
Enclosure Material: Lexan Polycarbonate
Environmental: Splash resistant and shock and vibration per RITRON Drop Test
(6 ft. drop onto concrete on all six sides)
Antenna Fitting: 1/4" - 32 x 1/4" threaded
External RF Test Jack: Antenna connector with RITRON SST-SRVBD test device
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SST-444 SPECIFICATIONS
GENERAL
Earphone Jack: 3.5 mm, disconnects the internal speaker for external earphone,
speaker / microphone, or headset. Also provides cable connection
for PC programming.
Microphone/PTT/Chg Jack: 2.5 mm, for external speaker/microphone, headset or RITRON
model BC-A wall charger
Push Button Controls:On/Volume Up
Volume Down/Off
PTT
Channel
Speaker Beep Indicators:
On/Volume UP Single beep when radio is turned on, followed by increasing audio
to adjust volume.
Volume Down/Off Decreasing audio to adjust volume, with two tones when unit is
turned off.
Both Volume Buttons Alternates between Tone Squelch (single beep) and Carrier
Squelch (two beeps). If both buttons are held down until the radio
beeps repeatedly, squelch will be disabled.
Channel Number of beeps indicates channel.
RECEIVER
Wide band Model Narrow band Model
Modulation Acceptance: +/- 7.0 KHz +/- 3.75 KHz
Sensitivity (12 dB SINAD): 0.25 µV 0.25 µV
Adjacent Channel (EIA): -60 dB -50 dB
Spurious Rejection: -60 dB -60 dB
Image Rejection (EIA): -70 dB -70 dB
Intermodulation (EIA): -56 dB -57 dB
Noise Squelch Sensitivity: Programmable per channel, factory set for 12 dB SINAD
Frequency Response: 300 - 3000 Hz, de-emphasized
Audio Output 1 Watt into 8 Ω, with less than 5 % THD @ the earphone jack
Receiving System: Dual conversion superheterodyne
I.F. System: 1st - 43.65 MHz 2nd - 450 KHz
L.O. Injection: Low side
QC/DQC Decode Time: per EIA Standards
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SST-444 SPECIFICATIONS
TRANSMITTER
RF Power Output: Programmable per channel for high or low power
High : 4 Watts (3.5 Watts minimum @ +7.2 VDC)
Low: 1 Watt
Wide Mode Narrow Mode
Emission Designator: 16K0F3E 11K0F3E
Deviation: +/- 5.00 KHz +/- 2.50 KHz
FM Hum and Noise: -43 dB -37 dB
Audio Distortion: < 3 % < 6 %
Spurious and Harmonics: -50 dBc
Audio Response: Meets FCC and EIA requirements
Time-out Timer: 60 seconds, programmable
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INTRODUCTION
GENERAL
RITRON's SST-444 handheld is a small, programmable two-way radio, designed to operate in the 460-
470 MHz professional FM communications band.
This handheld features push-button operating controls, with the Push-To-Talk and Channel buttons on
one side of the radio. The On / Volume Up and Volume Down / Off, volume and monitor controls are on
top.
Each radio can be “dealer or factory” programmed to contain a unique set of operating frequencies and
options. Selective signaling options include Quiet Call (CTCSS) and Digital Quiet Call (DCS). Transmitter
power, operating bandwidth and battery saver are among the options programmable on a per channel
basis.
Inspection
Each radio package should include a radio, antenna, rechargeable battery pack, belt clip and any optional
accessories ordered. Examine the equipment immediately after delivery and report any damages to your
shipping company.
Model Identification
The SST-444 model, serial number and FCC Identification are displayed on a label located on the back of
the radio beneath the belt clip.
FCC REGULATIONS
Licensing
The FCC requires the radio owner to obtain a station license for his radios before using them to transmit,
but does not require an operating license or permit.
The station licensee is responsible for ensuring that transmitter power; frequency and deviation are within
the limits specified by the station license. The station licensee is also responsible for proper operation and
maintenance of the radio equipment. This includes checking the transmitter frequency and deviation
periodically, using appropriate methods.
Safety Standards
The FCC (with its action in General Docket 79-144, March 13, 1985) has adopted a safety standard for
human exposure to radio frequency electromagnetic energy emitted by FCC regulated equipment.
RITRON follows these safety standards, and recommends that you observe the following guidelines:
•DO NOT hold the radio such that the antenna is very close to or touching exposed parts of the body,
especially the face or eyes, while transmitting. Keep the radio vertical, two to three inches away while
talking into the microphone.
•DO NOT press the Push-To-Talk except when you intend to transmit.
•DO NOT operate radio equipment near electrical blasting caps or in an explosive atmosphere.
•DO NOT allow children to play with any radio equipment that contains a transmitting device.
•Repair of RITRON products should be performed only by RITRON authorized personnel.
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BATTERY CARE
The handheld is powered by a rechargeable battery, which fits into the radio case (see FIG-1).
CHARGING
The battery pack can lose its charge during storage and shipment, and should be fully charged before the
radio is used. Thereafter, the battery should be charged overnight after each day of use, to ensure peak
radio performance for the next day. Using the cube charger (model BC-A), the battery should charge
completely in 12 hours.
Note: A new battery must be cycled (charged and discharged) several times before it will reach its
maximum charge capacity.
To charge the battery using a RITRON cube charger - plug the charger cord into the smaller of the two
jacks on top of the radio. Then plug the cube into a 110 VAC outlet. The green lamp lights while the
battery is charging, and should go off only when the cube is unplugged.
Two charger contacts, visible through the bottom of the radio case, allow the battery to be charged using
an optional RITRON drop-in charger (model BCPS-FS). The battery pack may be charged inside or
outside of the radio case.
To charge the battery using a drop-in charger (model BCPS-FS) - plug the drop-in charger into a 110 VAC
outlet. Set the portable or battery into the charger. Each battery contact must rest on a charger contact
pin.
Typically, a battery pack’s service life is one year. To ensure maximum service life, follow these
guidelines:
•Do not discharge a battery that is already “run down.” If the battery cannot power your radio, recharge
the battery.
•Do not overcharge a battery. The standard battery should not be left to charge continuously.
•Before storing a battery, charge it for 16 hours. Thereafter, charge the battery for 16 hours once every
30 days.
With daily use and recharging, a battery’s service life is about one year. It is time to purchase a new
battery:
1) When the radio’s transmitter coverage decreases or does not work at all.
2) When the radio quits working after just a few hours of use, even with a full overnight charge.
3) When the battery is more than two years old. The date of manufacture is stamped on every battery.
The first two digits indicate the year, the last two digits the week.
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BATTERY CARE
BATTERY REPLACEMENT
To take the battery out of the radio, remove the battery door pictured in FIG-1. Use the pull-tab to remove
the battery.
Slide the replacement battery into the radio case. Make sure the spring contacts are inserted between the
battery and paper insulator. The contacts must not touch the radio PC board.
PRECAUTIONS
•Use only RITRON-supplied chargers; other chargers might cause fire, explosion, or other damage to
the radio.
•Do not "fast-charge" a brand new battery pack. Otherwise, the battery might be damaged.
• Once the battery has been charged fully using the normal rate, the fast rate may be used thereafter.
•Do not fast-charge a battery pack that is fully charged. This can shorten battery life.
•Do not charge or replace a battery in an explosive atmosphere. Contact sparking can ignite an
explosion.
•Do not dispose of a battery in fire. An explosion might result.
•Do not charge the battery in temperatures colder than about 45°F. Electrolyte leakage can occur and
ruin the battery.
•Charging in temperatures above approximately 95°F will not harm the battery, but can reduce its
charge capacity.
Fig. 1
Battery Replacement
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DESCRIPTION OF CONTROLS AND CONNECTORS
Antenna
The flexible antenna radiates and receives radio signals. Before using the radio, be sure the antenna
base is threaded fully into the radio’s antenna bushing.
VHF and UHF antennas are not interchangeable. Use only the antenna type packaged with the radio. A
VHF antenna is pictured in FIG-2. (The UHF antenna is smaller in diameter.)
On/Volume Up
This button switches on the radio, then increases the volume if you continue to press.
Off/Volume Down
This button decreases the volume, then shuts off the radio if you continue to press.
Channel Select
Pressing this button selects the next channel. When the maximum number of channels is reached and
you press this button, the radio resets to channel 1.
Speaker
The speaker allows you to hear calls on your channel.
Push-To-Talk Button
The PTT activates the transmitter, and must be held down while you talk into the microphone. Release
the PTT button to receive.
Microphone
The microphone converts your voice into electrical impulses, which are carried with your broadcast to
receiving radios. Hold the radio about two inches away and talk into the microphone while transmitting.
Shouting does not improve the listener’s reception.
Audio Accessory Jack
This jack connects speaker audio to optional accessories, such as a remote speaker/microphone or an
earphone. For accessories that have a two-plug connector, the smaller plug is inserted into the charge
jack.
This jack is also used to program the radio using the optional PC programming kit.
Charge Jack
The battery may be charged through this jack using a standard RITRON wall socket charger cube.
This jack also connects microphone audio to the optional remote speaker/microphone.
Battery Access (Case Bottom)
The battery door on the case bottom may be removed to access the battery. (Refer to the battery section
of this manual.)
Drop-in Charger Contacts
Two charger contacts in the bottom of the SST-444 radio case allow the battery pack to be charged using
an optional RITRON drop-in charger (model BCPS-FS).
Jack Cover
This rubber cover seals out dust and moisture, etc. Snap the cover into the audio accessory and charge
jack openings when the jacks are not being used.
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DESCRIPTION OF CONTROLS AND CONNECTORS
CH
ON OFF/HOLD
VOLUME
Belt Clip Installation
If you are going to attach the belt clip to the handheld, follow these instructions:
1) The belt clip is fastened to the radio case back with the Philips head screw provided. Use the screw
included, since a longer screw might damage the radio’s electronics.
Do not use petroleum solvents of any kind on the radio. These can corrode the case.
2) Place the belt clip on top of the radio case back, with the screw hole in the aligned with the hole in the
radio case.
3) Using the screw that came with this accessory, attach the clip to the radio.
Antenna
Vol Down/Off
On/Vol Up
Audio Accessory Jack
Jack Cover
Charge Jack
Speaker
Microphone
Push-to-Talk
Channel Selector
Battery Access Door
(Case bottom) Battery Charger Contacts
(Case bottom)
Fig. 2 Controls and Accessory Connectors
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OPERATION
On-off/Volume
To switch on the radio - press the on/volume up button.
To adjust the volume - press the volume up button until you reach the desired level. You should hear
noise and any broadcasts on the channel.
To turn off the radio - press and hold the off/volume down button until two tones sound.
To determine whether the radio is on - press the volume down button. If the radio is on, noise or activity
on the channel is heard.
Receive
To hear calls from other users - adjust the volume as desired. The radio can receive broadcasts while the
Push-To-Talk button is not being pressed. Whether or not you hear these broadcasts depends upon the
squelch settings.
There are two types of squelch used in the SST-444 portable. First is carrier squelch. This lets you hear
all broadcasts on your channel strong enough for the radio to detect, and silences noise. Second is one of
the selective signaling or “tone squelch” formats available on the SST-444. This allows you to screen out
“on-channel” broadcasts that do not carry the correct code programmed for the radio.
Note: It is possible that the beginning of a call might be missed while the radio is in battery saver mode. If
this happens, ask the caller to repeat his message.
Monitor
To monitor the channel - press one of the volume control buttons. When you press the volume up or the
volume down button, squelch turns off and all radio traffic on the channel (and noise) sounds in the
speaker.
Selective Signaling Squelch
To activate tone squelch - simultaneously press both of the volume buttons. Hold for a second or two
before releasing. When tone squelch is turned on, the handheld sounds one beep. When carrier squelch
is on, the radio emits a "double beep."
Note: If you continue to hold down the volume buttons after the beep (or double beep), the radio will start
beeping repeatedly. This means that squelch is turned off. Release the buttons. To restore squelch,
press and hold both of the volume buttons until the radio sounds a beep or double beep.
Battery Saver
The handheld has a programmable "battery saver" feature that conserves battery power. The battery
saver constantly checks the radio's transmitter, receiver and controls for activity. If a number of seconds
pass without the receiver detecting a call, and without the user operating a control, this feature removes
power from most of the radio.
During this "off-time," any activity restores full power. Every few fractions of a second, the battery saver
applies power to the receiver, checking for broadcasts. It is possible that the first part of an incoming call
might go unheard before activity is detected and power restored. If this happens, the caller can repeat his
message. Once "radio contact" is made, normal unhurried conversation can follow.
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OPERATION
Transmit
Normally, you should not transmit until no one is talking on the channel.
To transmit - hold down the Push-To-Talk button and, with the radio a couple of inches away, talk into the
microphone. Speak in a normal tone, since talking louder will not improve the listener’s reception.
Channel Selection
To change channels - press and release the channel button. The radio will beep a number of times equal
to the new channel number. For example, if you select channel 2, the handheld will beep twice. If the
highest channel number is selected and you press the channel button, the radio will reset to channel 1. A
one-channel radio will beep only once when you press the channel button.
WHAT THE RADIO TONES MEAN
The handheld responds to certain instructions by sounding a beep or series of tones. These tones can tell
you whether the radio is working as you expect.
Power On/Self Check “OK”
When the handheld is turned on, it will run a quick “self test.” Once the internal system checks confirm
basic functions, the radio sounds a brief “confirmation tone.” The radio is then ready to use.
Error Tones
However, if the “self test” detects a diagnostic error, an error tone sounds. Alternating tones (the second
is longer and lower pitched) indicate the radio frequency synthesizer is malfunctioning. Turn off the radio
and try again. A long, low-pitched tone means the battery voltage is too low to operate the radio. In this
case, recharge the battery. If you cannot correct a problem, consult an authorized Ritron service facility or
Ritron.
Channel Select
When the channel button is pressed, the radio beeps a number of times equal to the channel number
selected.
Tone Squelch
When you press and hold both Volume buttons at the same time, a single beep will sound to indicate that
tone squelch is on. A "double beep" means that carrier squelch is on.
Recharge Battery Alert
As the battery voltage approaches the minimum required “operating voltage” the radio will emit a short
beep every minute to alert the user that the battery will soon need recharging. Once the battery charge
drops below the required "operating voltage," the radio emits a long, low tone and turns itself off. If you
turn the radio back on, it will beep again and shut itself off. Recharge the battery.
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OPERATION
OPTIONAL RADIO TONES
The SST-444 can be programmed using the RITRON PC Programmer for optional alert tones.
Receive Squelch Tone
A short tone sounds at the end of each received transmission to indicate that you may transmit.
Busy Channel Transmit Inhibit
If a user is transmitting on your radio frequency without your tone, you will not be allowed to transmit. The
radio will beep a series of long, low tones while the PTT is held down (like a busy signal).
Transmitter Time Out
A low tone followed by a higher-pitched tone sounds and the transmitter automatically shuts off if you hold
down the PTT button longer than the programmed Time-out. The radio automatically switches to receive
mode. Authorized service personnel can turn off this feature.
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OPERATION
TROUBLESHOOTING
If you have trouble operating the handheld, review the radio controls and operation sections. If you think
the radio is malfunctioning, check the table below.
Problem Possible Solutions
GENERAL
The radio does not work at all. Make sure that the battery is installed correctly, as shown
in FIG-1.
Recharge or replace the battery. (See note 1.)
Operating features do not work exactly The radio has been factory or dealer programmed for
As expected. customized operation.
Reception is poor. Move to a different location. (Note 2.)
Confirm that the proper antenna is connected to the radio.
(See p. 11, "Antenna.")
You cannot hear calls from other radios. Turn off tone squelch. (See Note 3.)
Be certain your radio receives on the same as the caller
transmits. (Note 4.)
Recharge the battery. (Note 1.)
Your calls cannot be heard in other radios. Make sure that your radio transmits on the receive
frequency of the radio(s) you want to call. (Note 4.)
Recharge the battery. (Note 1.)
Battery
The battery loses its charge sooner than Review the battery charging instructions.
expected. Conserve the battery. (Note 5.)
If the radio is used in extreme cold, warm the radio under
your coat. (Note 6.)
Replace the battery. (Note 1.)
Error Tones
An error tone sounds when the radio is first See "Error Tones" in the Operation section.
switched on.
An error tone sounds while you are talking Refer to “Error Tones”
(and the transmitter shuts off).
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OPERATION
TROUBLESHOOTING
Problem Possible Solutions
Tone Coded Squelch
You cannot screen out calls from users Make sure the channel is programmed with tone squelch.
outside of your tone group. Activate Tone (coded) squelch. (Note 7.)
You cannot hear Tone coded messages Confirm that the channel is programmed to detect the
while in Tone (coded) squelch. same code as the calling radio(s) transmits. (Note 7.)
Others in your tone group cannot hear your Verify that you transmit the same code as the radio(s) you
tone coded messages. call are programmed to detect. (Note 7.)
Notes
1) Try a battery pack from a working radio. If the radio in question works with that pack, the original
battery is suspect. Charge the suspect battery as recommended in this manual. Then, if the charged
original battery cannot power the handheld, try charging again with another charger. If the battery still
doesn’t hold a charge, the pack should probably be replaced. However, if the battery appears to be
good after you try the second charger, the first charger might be faulty. If you think that an accessory
is not operating properly, contact your dealer or RITRON. (Radio accessories come with a 90-day
limited warranty.)
2) Reception can often be improved by moving a short distance. This effect is more noticeable inside of
buildings. The range of these portables equipped with a standard battery pack is about two miles
(line-of-sight).
3) If your radio does not detect calls from other radios on the channel, turn off tone squelch. (Press both
Volume buttons at the same time - a double beep means that tone squelch is off.)
4) If you want to hear a call, you must select a channel that is programmed to receive the caller’s
transmit frequency. If you want to call another unit, you must select a channel that is programmed to
transmit the other radio’s receive frequency. However, if you use a repeater, your channel must be
programmed to work with the repeater’s transmit and receive frequencies. (A radio channel can hold
two separate operating frequencies, one for Receive, the other for Transmit.)
5) Maximum power drain occurs while the radio transmits, so don’t hold down the Push-To-Talk button
more than necessary. Battery power is used while the handheld is left on to receive calls. If practical,
switch off the unit.
6) In extreme cold, a battery’s charge capacity is greatly reduced. If you use the radio in very cold
weather, periodically warm the portable underneath your coat if possible. An optional remote
speaker/microphone would allow you to keep the radio under your coat while transmitting and
receiving.
7) In order for radios to communicate using Quiet Call, they must be programmed with the same tone
code. Each code is unique, and your radio will respond only to the code programmed.
Press and hold both volume buttons at the same time. A single beep means that tone squelch is on.
A double beep means that tone squelch is off.
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18
PROGRAMMING THE RADIO
Each SST-444 may be programmed to operate on up to 4 channels. The SST-444 may be programmed
using its Push-to-Talk switch or an optional RITRON programming kit.
PTT (PUSH-TO-TALK) PROGRAMMING allows you to program any channel to one of the radio
frequencies listed in Table 1 and any Quiet Call code listed in Table 2. The radio will transmit and receive
on the programmed table frequency and QC code.
PC PROGRAMMING allows you to program any frequency within the band and channel spacing of the
radio model. This method also lets you customize the handheld with optional operating features.
PTT (PUSH-TO-TALK) PROGRAMMING
Placing the Radio in PTT Programming Mode
1. Turn off the radio by pressing the Volume Down button until the “radio off” prompt sounds.
2. Press and hold the PTT button.
3. While holding the PTT button, press and hold the Volume On button until a rapid beeping is heard in
the speaker.
4. Release the PTT and Volume On buttons. A series of three ascending tones will sound in the speaker
indicating that the radio is in PTT program mode.
Note: If the radio will not enter PTT program mode, this feature has probably been turned off using the
optional PC programming kit.
How to Find Out What Is Already Programmed
1. Place the radio in PTT programming mode as described above.
2. Press the Channel button to select the radio channel you would like to read out.
3. Press the Volume Up button.
4. The radio will sound a series of beeps, pause, and then begin another series. Four series of beeps
will be heard, with each series representing a digit. The number of beeps in a series is equal to the
digit. (10 beeps = the digit 0)
5. Write down each digit while the radio pauses. List the digits in the order that you hear them.
6. The first two digits represent the frequency as shown in Table 1.
7. The second two digits represent the QC (CTCSS) tone frequency as shown in Table 2.
Note: If you are unable to read out a channel, it has probably been programmed using the PC
programming kit to a frequency not contained in Table 1.
19
PROGRAMMING THE RADIO
PTT Programming the Radio
Four valid digits must be entered for the radio to accept PTT programming. The first two digits entered is
the frequency code from Table 1, followed by the two digits for the QC code from Table 2.
1. Place the radio in PTT programming mode as described above.
2. Press the Channel button to select the radio channel you would like to program.
3. Enter the first digit by pressing the PTT button the number of times equal to the digit’s value.
(To enter the digit 0, press the PTT ten times.)
4. Pause after the digit is entered, a tone will sound indicating that the digit has been accepted.
5. Enter the second, third and fourth digits using the same method as the first digit.
6. Press the Volume Up button to enter the new channel programming. The radio will sound a
confirmation tone to indicate that programming has been accepted.
PTT Programming Mistakes
Invalid Entries An error tone means that you tried to save an invalid entry. No programming
changes are made in this case. A triple tone will sound next indicating that the
radio is still in programming mode, and ready for an entry.
PTT Entry Mistakes If you press the PTT five times when you intended four, for example, or if you just
lose count, do not press the Volume Up button to store the entry. Instead, start
over by turning the radio off and placing the radio in programming mode again.
Return To Normal Operation
After you finish programming, turn the radio off and then on again. The radio will beep when it is ready for
normal operation.
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20
PROGRAMMING THE RADIO
Table 1 – PTT Programming Frequency Table
Code Frequency Description Code Frequency Description
01 467.7625 J 11 462.6250 Black Dot
02 467.8125 K 12 462.6750 Orange Dot
03 464.5500 Yellow Dot 13 464.3250
04 464.5000 Brown Dot 14 464.8250
05 467.8500 Silver Star 15 469.5000
06 467.8750 Gold Star 16 469.5500
07 467.9000 Red Star 17 463.2625
08 467.9250 Blue Star 18 464.9125
09 469.2625 19 464.6000
10 462.5750 White Dot 20 464.7000
Table 2 – Quiet Call Codes and Frequencies
QC Freq QC Freq QC Freq QC Freq
Code (Hz) Code (Hz) Code (Hz) Code (Hz)
01 67.0 16 114.8 31 192.8 46 189.9
02 71.9 17 118.8 32 203.5 47 196.6
03 74.4 18 123.0 33 210.7 48 199.5
04 77.0 19 127.3 34 218.1 49 206.5
05 79.7 20 131.8 35 225.7 50 229.1
06 82.5 21 136.5 36 233.6 51 254.1
07 85.4 22 141.3 37 241.8
08 88.5 23 146.2 38 250.3
09 91.5 24 151.4 39 69.4
10 94.8 25 156.7 40 159.8
11 97.4 26 162.2 41 165.5
12 100.0 27 167.9 42 171.3
13 103.5 28 173.8 43 177.3
14 107.2 29 179.9 44 No Tone
15 110.9 30 186.2 45 183.5
COMPUTER SOFTWARE COPYRIGHTS
The RITRON, Inc. products described in this manual include copyrighted RITRON, inc. computer
programs. Laws in the United States and other countries grant to RITRON, inc. certain exclusive rights in
its copyrighted computer programs, including the exclusive right to distribute copies of the programs,
make reproductions of the programs, and prepare derivative works based on the programs. Accordingly,
any computer programs contained in RITRON, inc. products may not be copied or reproduced in any
manner without the express written permission of RITRON. The purchase of RITRON, inc. products does
not grant any license or rights under the copyrights or other intellectual property of RITRON, inc., except
for the non-exclusive, royalty fee license to use that arises in the sale of a product, or as addressed in a
written agreement between RITRON, inc. and the purchaser of RITRON, inc. products.
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21
PROGRAMMING THE RADIO
PROGRAMMING THE RADIO USING A PC COMPUTER
RITRON’s programming kit allows programming of the SST-444 model radios using a PC compatible
computer. An adapter cable connects the radio to a computer’s serial communications port. Once the
cable is hooked up, the user inserts the diskette provided into his computer’s floppy disk drive and loads a
software program.
This program transfers data between radio and computer memory, and includes on-screen instructions
and help. Radio data may be saved to the computer’s hard disk in order to program other radios.
The PC Programming Kit Includes:
1) Ritron Transceiver programming software, which is contained on 3.5" diskettes.
2) Installation instructions and a registration form.
3) Ritron PC to radio adapter cable, which is terminated at one end with a DB-25F connector, at the
other end with a modular plug. The DB-25 plugs into the computer’s serial port, the modular plug into
the SST-SRVBD modular jack.
4) An adapter for use with SST-444 portables. This adapter mates the modular plug to a 3.5 mm plug,
for connection to the handheld audio jack.
The PC Programming Kit Requires:
A PC compatible computer with Windows 95 or later. The computer must have an RS-232 serial port
available. A hard disk drive is recommended.
Programmable Features
The following features may be programmed on a per channel basis, or will affect all channels together.
Feature Range Standard Setting Per Channel
Automatic Inactivity Turn-off Yes - No Yes
Battery Saver Enable Yes - No Yes
Battery Saver Off Time - -
Beep Volume Level Fixed – Controlled Fixed
Beep Fixed Volume Level - -
Busy Channel Transmit Inhibit Yes - No No √
Carrier Only, No Tones or Codes - - √
Channel Selection Mode Increment - Enter Increment
Digital Tone Invert RX Yes - No No √
Digital Tone Invert TX Yes - No No √
Digital Quiet Call (DCS) - - √
Disable Monitor Yes - No No √
Channel Beep Rate Slow - Fast Slow
Narrow Band Channel Yes - No No √
Quiet Call (CTCSS) See Table 2 - √
Quiet Call Encode Only Yes - No No √
Receive Squelch Tone Yes - No No √
Squelch Tightener Yes - No No √
Transmit Power Low - High High √
Transmit Time Out Timer (60 s) Yes - No Yes
Turn On To Medium Volume Level Yes - No Yes
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22
PROGRAMMING THE RADIO
Descriptions of Features
Automatic Inactivity Turn-off - The radio automatically shuts itself off if four hours go by without the
microcontroller detecting input from the volume, PTT or channel controls.
Battery Saver - Enabling this option allows the radio to go into battery saver mode when the radio remains
idle. The power strobe begins after eight seconds of inactivity.
Battery Saver Off Time - This is the cycle time that the radio is off in battery saver mode before it checks
for a received signal. A long Battery Saver Off Time may cause the user to miss the beginning of the first
message when in battery saver mode.
Busy Channel Transmit Inhibit - This keeps the radio from broadcasting if the channel is busy, and is often
used in conjunction with Disable Monitor. If you press the PTT when the channel is busy with a signal not
intended for your radio (not carrying your tone code), this feature sounds a "busy" tone in the speaker and
keeps the transmitter turned off.
Channel Selection Mode - This feature allows the channel selector to increment or enter the channel. The
channel number is "beeped out" when the channel button is first pressed. The channel is not changed. In
increment mode the radio is changed to the next available channel if the channel button is pressed again
within three seconds. In enter mode the user must press the channel button the number of times equal to
the channel they wish to select.
Digital Quiet Call RX Invert - The programmed code is inverted for receive mode only.
Digital Quiet Call TX Invert - The code is inverted for transmit mode.
Disable Monitor - This function may be programmed to keep the radio user from listening to other
licensees on a shared channel. QC, DQC or trunking must be used with this option (although, not the
Encode Only feature).
Quiet Call (CTCSS) - Programming a Quiet Call code allows you to screen out transmissions that do not
carry your code. Your code is broadcast when you press the PTT to make a call.
Quiet Call Encode Only - The Quiet Call code programmed for the channel is transmitted with your calls.
However, Quiet Call is turned off during receive mode, allowing all traffic on the channel to be heard.
Receive Frequency - The radio frequency that receives broadcasts from other units.
Receive Squelch Tone - The receiving radio beeps at the end of each received transmission.
Squelch Tightener - This feature reduces distant "co-channel" or other interference for channels that are
not programmed with Quiet Call. Carrier squelch is set for maximum sensitivity at the factory, but may be
adjusted to mute weak signals
Transmit Time Out Timer - This feature automatically shuts off the transmitter (ending your call) if you hold
down the PTT button continuously for 60 seconds. The radio sounds a tone when the transmitter shuts
off.
Turn On To Medium Volume Level - The volume level is at mid-range when the radio is first turned on.
Normally, the volume level is low when the radio is turned on.
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23
SST-444 THEORY OF OPERATION
INTRODUCTION
The SST-444 is a four-channel handheld transceiver built on a single multi-layer printed circuit board.
Both sides of the main printed circuit board are populated with components, with the bottom side
containing only surface mounted components.
The SST-444 is frequency synthesized, with all functions of the radio controlled by microcontroller.
POWER SUPPLY AND VOLTAGE DISTRIBUTION
The SST-444 is powered by an internal 6-cell rechargeable battery pack. The battery pack supplies power
to the radio via two contact terminals that are connected to the PCB through P302. F301 is a 3A fuse in
series with P302 for short circuit protection. The battery pack may be charged through 2.5 mm charge
jack J301 via CR302 and F301. Zener diode CR301 prevents the batteries from discharging through the
charger accessory, stops a reverse voltage from being applied to the battery pack through J301, and
prevents a high voltage from being applied to the radio circuitry.
SW301 ON/VOL UP switched is pressed to switch on the SST-444, turning on voltage pass transistor
Q304 via R302. Q304 supplies power to IC309, a +5 VDC regulator used to power microcontroller IC301.
Pin 13 of IC301 turns on Q303, which keeps Q304 turned on after SW301 has been released. Power is
removed from the SST-444 by pressing the VOL DN/OFF switch SW302 until a beep is heard from the
speaker, at which time Q304 is turned off.
+5 VDC regulator IC309 supplies power directly to microcontroller IC301, bilateral audio gates IC304,
reference oscillator Y302, synthesizer IC401, and PTT detect transistor Q302.
The T/R output at Pin 11 of IC301 lets Q101 switch the regulated +5 VDC to the receiver. Pin 11 of IC301
will also turn on Q202, which turns on voltage pass transistor Q204. With Q204 emitter connected to the
+VBATT battery supply, the collector output is connected to the emitter of Q202 through voltage divider
R202/R203, whose values are selected to limit the TX+V voltage to +6 VDC.
Power Strobe
The SST-444 handheld includes a power strobe feature, which reduces battery current drain by
periodically removing voltage from part of the radio. The strobe off cycle time is programmable using the
PC Programming Kit. The +5VSW power strobe output at Pin 10 of IC301 controls Q306, which switches
the regulated +5 VDC to the audio processing circuitry and the synthesizer circuitry. This includes IC303A
2.5 VDC (Vag) for bias on audio processing circuitry, IC303C audio high pass filter, IC308 and IC305A
audio low pass filter for sub-audible frequencies, IC305B audio limiting amplifier, IC306 digital
potentiometers, IC303B audio summing node amplifier, and IC303D audio low pass filter.
Low Battery Voltage Detection
Battery voltage is measured at A/D input Pin 16 of IC301 through voltage divider R303/R305. The radio
will emit a periodic beep if low battery voltage is detected, and will turn the radio off if the battery voltage
drops below +5 VDC. This is to protect the microcontroller and its EE memory from corruption due to low
supply voltage.
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24
SST-444 THEORY OF OPERATION
REFERENCE OSCILLATOR
Reference oscillator Y302 is a 1.5 ppm temperature controlled, voltage controlled oscillator (TCVCXO)
operating at 14.4 MHz. The Pin 4 output of the TCVCXO provides a reference for the frequency
synthesizer IC401 at Pin 20. IC401 is programmed to provide an output at Pin 1 that is ¼ of the reference
(3.6 MHz), which is applied as a reference oscillator to Pin 27 of IC301 microcontroller. The Y302 pin 4
output is also multiplied up to 43.2 MHz by Q105 and its associated circuitry to provide a receiver 2nd local
oscillator signal.
SYNTHESIZER
The SST-444 radio is built around a common phase-locked loop (PLL) that consists of a voltage-controlled
oscillator (VCO) and a frequency synthesizer. The PLL generates both the receiver 1st local oscillator and
transmitter carrier signals. Control signals from microcontroller IC301 and Reference oscillator Y302 are
routed to frequency synthesizer IC401 per the following chart:
Pin Numbers
Clock Data Latch LD T/R SW REF IN REF OUT +5SW +5V
IC301 12 5 20 12 11 - 27 10 -
Y302-----4--2
IC401 18 19 17 2 - 20 1 12 5, 14
Q404, CR401, C414 and associated components provide a filtered supply for the VCO oscillator and
buffer amplifiers.
Prescaler Divider / Synthesizer Controller
IC401 contains both a prescaler and synthesizer controller. The prescaler squares and divides the VCO
output present at pin 11 by either 64 or 65, determined by a synthesizer controller logic signal. The exact
number of times the prescaler is instructed to change divisors is determined by the channel frequency.
IC401 contains a digital phase detector that works as follows: when an operating channel is changed or
the receive/transmit mode switched, a new synthesizer operating frequency is selected. Microcontroller
IC301 clocks new data into IC401 internal buffer in synchronization with clock pulses. The channel
information is stored in EE memory of IC302 and is loaded into RAM when the channel is selected.
Once new data is loaded into the buffer, a single pulse from IC301 appears at IC401 to instruct the
synthesizer controller to latch and execute the new data. IC401 utilizes internal circuitry to determine
whether the present VCO output frequency is correct by comparing the phase and frequency of the VCO
signal at Pin 11 to the 14.4 MHz reference oscillator at Pin 20. IC401 produces an output signal at Pin 6,
a single-ended phase/frequency detector output, proportional to the phase difference between the two
input signals.
The loop filter C429, C427, R419, R420, R418, and C426 transform the Pin 6 output signal to a DC
voltage for application to the VCO tuning varactor CR402. The synthesizer system is “locked” when the
phase and frequency of both the reference and the divided VCO signal are the same.
The maximum amount of current this output can sink or source is determined by the value of R421 tied to
Pin 8 of IC401, with the output current programmable to 25, 50 or 100% of maximum.
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25
SST-444 THEORY OF OPERATION
VCO / Buffer Amplifiers
Q403, L401, CR402 and associated components form the VCO (Voltage Controlled Oscillator), a resonant
circuit that oscillates at frequencies from 416 MHz in receive (receive frequency - 43.65 MHz) to 470 MHz
in transmit. Varying the voltage at CR402 changes the varactor capacitance, which in turn alters the VCO
output frequency. When in transmit mode a +5 VDC T/RSW signal is applied to Q406, which turns on
Q405 to draw current through pin diode CR404 and L403. With CR404 biased on, L402 is effectively
shorted to ground, shifting the VCO frequency up 43.65 MHz. Q401 and Q402 are buffer amplifiers, with
Q401 feeding in the input of the synthesizer at Pin 11, the receiver 1st local oscillator and the transmitter
pre-amplifier.
Oscillator Modulation
When the SST-444 is in transmit, modulation balance control IC306E passes TX audio through to the
VCO modulation input at R416. TX audio is applied to varactor CR403 to modulate the VCO. TX audio is
also routed to the Pin 1 input of TCVCXO reference oscillator Y302. Low frequency tones modulate the
reference oscillator because the synthesizer is not able to track them.
DIGITAL POTENTIOMETERS
IC306 contains 6 digital potentiometers programmed by IC301, sharing the same clock and data outputs
used by the synthesizer and a separate Digital Pot Latch signal from Pin 8. The digital potentiometers are
used in conjunction with IC303B, a summing node amplifier used for modulating the VCO and reference
oscillator. IC306A, B, D, E, and F can only be changed through serial programming, and can only be
performed by an authorized licensed RF technician.
IC306A is connected through R352 to the Pin 6 input of IC303B. IC306A adjusts the DC output of IC303B
to tune the reference oscillator frequency.
IC306B is connected to the Pin 2 Gate control of RF power transistor Q203 to adjust transmitter power
output.
Volume control IC306C applies the processed voice band signals at IC303D to audio amplifier IC307
when in receive mode. Depressing the ON/VOL UP switch SW301 increases the setting of IC306C while
VOL DN/OFF switch SW302 decreases it.
Transmitter tone deviation control IC306D applies the output of the selective signaling low-pass filter
IC308 to the Pin 6 input of IC303B through R350. IC306D is completely closed in receive mode.
Transmitter modulation balance control IC306E is used to apply the Pin 7 output of IC303B to the VCO
modulation input. This will set the ratio of the modulating signal applied to the VCO and the reference
oscillator. IC306E is completely closed in receive mode.
Transmitter voice deviation control IC306F applies the processed voice band signals at IC303D to the Pin
6 input of IC303B through R349. IC306F is completely closed in receive mode.
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26
SST-444 THEORY OF OPERATION
RECEIVER
As mentioned before, Q101 switches the regulated +5 VDC to the receiver. The +VRX receiver voltage is
switched at the strobe duty cycle if programmed for power strobe.
RF Amplifier
A received signal from the antenna passes through a low-pass filter (L207, C216, C217, L206, C101, and
C202) to the receiver headend. L101 and the associated capacitors form a bandpass filter ahead of low-
noise RF amplifier Q102. L101 and C103 provide a notch at the image frequency, 87.3 MHz below the
receive frequency. The amplified RF signal is applied to a 2-pole bandpass filter consisting of L103, L104,
and associated capacitors. This circuit can be tuned for any 10 MHz band between 450 and 470 MHz.
1st Mixer
The amplified received input signal is applied to the gate of FET mixer Q103. The 1st local oscillator
signal from the synthesizer module is applied to the source of Q103. L106, C117 and C118 tune the drain
output of Q103 to 43.65 MHz and apply it to YF101, a 43.65 MHz two-pole crystal filter. Q104 and
associated components amplify the 43.65 MHz IF signal and apply it to the input of the 2nd mixer at Pin 16
of IC101.
FM Receiver Subsystem
A multi-function integrated circuit, IC101 and associated components for the FM-receiver subsystem. The
subsystem performs the following functions: 1) 2nd mixer, 2) 2nd IF amplifier, 3) FM detector, and 4)
noise amplifier.
The Pin 4 output of 14.4 MHz reference oscillator Y302 is multiplied up to 43.2 MHz by Q105 and
associated components. This signal is applied to the 2nd local oscillator input at Pin 1 of IC101. The
43.65 MHz signal at Pin 16 and the 2nd local oscillator are mixed, with the resulting 450 KHz output signal
appearing at Pin 3. This signal is filtered by a 450 KHz 6-pole ceramic filter YF102 and applied to the
input of the limiting IF amplifier at Pin 5. IC101 Pin 6 is the de-coupled input to the IF amplifier, Pin 7 the
limited IF output signal. An internal quadrature detector, whose center frequency is determined by 450
KHz quadrature coil T101, detects the FM IF signal. One input of the quadrature detector is connected
internally to the IF signal at Pin 7, while the other input is the phase-shifted signal from T101 at Pin 8.
Demodulated audio appears at Pin 9, where a low-pass filter (R114, C130) removes spurious quadrature
output prior to application to the voice/tone conditioning audio circuitry. Demodulated audio from Pin 9 is
applied to the Pin 10 input of a noise filter/amplifier consisting of R112, C123, C124, R110, R111 and
R113. The Pin 11 output of the noise amplifier is applied to a biased noise detector CR103, with the
output connected to an A/D input of IC301 at Pin 19. The SST-444 is serial programmed to set the
squelch threshold and hysteresis.
Voice / Tone Conditioning in Receive Mode
SST-444 audio conditioning filter circuits are shared with the transmitter. The same high-pass
filter/amplifier (IC303C and associated components) used in receive voice band conditioning is used in the
transmit band. Similarly, the low-pass filter (IC308 and associated components) used for selective signal
tone decode filtering is also used for selective signal encoding. Altering circuit configuration with bilateral
switches IC304A, B and C permits the use of the same audio filtering system for both transmit and receive
modes.
After R114 and C130 remove the 450 KHz element from the demodulated audio output at Pin 9 of IC101,
C333 couples the audio signal to bilateral switch IC304C for subaudible tone detection and connection to
IC304A for voice band audio processing.
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27
SST-444 THEORY OF OPERATION
Voice Band
Bilateral switch IC304A passes the received audio signal to the input of IC303C, which along with its
associated components for a high-pass filter/amplifier circuit that attenuates audio signals below 300 Hz.
The output of IC303C is applied to the input of IC305B limiting amplifier. Bilateral switch IC304B is
switched in receive to insert C351 into the feedback circuit of IC305B, providing de-emphasis of the
received audio signal. Bilateral switch IC304B also removes R335 from the Pin 6 input to reduce the gain
and prevent limiting. The output from IC305B is applied to the input of IC303D, which along with its
associated components form an 18dB/octave low-pass filter for frequencies above 3000 Hz. The output
of IC303D is connected to IC306C volume control prior to connection to audio amplifier IC307. The output
of IC303D is also connected to IC306F voice deviation control, which is completely closed in receive mode
to prevent received signals from modulating the VCO and reference oscillators.
Audio frequency tones from Pin 23 of microcontroller IC301 are applied to the Pin 6 input of IC305B to
provide the SST-444 alert tones.
Sub-Audible
Bilateral switch IC304C passes the received audio signal to the input of IC305A, which amplifies the signal
and applies it to the Pin 2 input of IC308, a 5-pole low-pass filter that attenuates frequencies above 250
Hz. The output at Pin 5 is applied to an A/D input of IC301 at Pin 18 for tone decoding. An internal digital
signal processing routine programmed into microcontroller IC301 is used to decode the correct selective
signaling code. The output at Pin 5 of IC308 is also connected to tone deviation control IC306D, which is
completely closed in receive mode to prevent received subaudible tone signals from modulating the VCO
and reference oscillators.
Audio Amplifier
Receive audio from volume control IC306C is applied to the Pin 2 input IC307, a 1 Watt audio amplifier.
C365 couples the Pin 5 output to the internal 8Ω speaker SP301 via audio jack J303.
Microcontroller IC301 Pin 22 switches DC power to the audio amplifier by turning on Q07, which then turns
on pass transistor Q308 to apply battery voltage to Pin 6 of the audio amp. CR307 prevents an
inadvertent DC voltage at J303 from damaging the audio amplifier.
ANTENNA SWITCHING / LOW PASS FILTER
A low-pass filter comprised of filter L203, C213, C214, L204, C217, L207, and C216 removes harmonics
from the transmitter output before applying the RF signal to the antenna. Received signals pass through
the low-pass filter before entering the receiver RF amplifier circuitry.
Two PIN diodes (CR201, CR101) and associated components form the antenna switching circuit. With
the SST-444 in receive mode, no voltage is applied to the PIN diodes and they do not conduct. This
reverse biases CR201 to prevent the transmitter amplifier from affecting the receiver tuning and removes
CR101 from the receiver input. Incoming signals from the antenna pass through the low-pass filter, then
L206 and C102 to the receiver headend.
When the SST-444 is switched into transmit mode, transmitter supply voltage is switched on by Q201 and
Q202 and applied to R207. Current flows through R207, L205, CR201, L206 and then CR101 to ground,
forward biasing the PIN diodes. CR201 passes transmitter RF power to the antenna while CR101 shunts
the receiver RF amplifier input to ground. L206 provides sufficient impedance to isolate the transmitter
power from the receiver RF amplifier.
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28
SST-444 THEORY OF OPERATION
TRANSMITTER
Keying
The SST-444 transmitter is keyed when PTT switch SW304 is depressed. Electret condenser
microphone M301 is connected in series to ground with the PTT switch, which when depressed draws
current through M301, SW304, CR304 and R307 to turn on pass transistor Q302. Q302 then turns on
Q301 to pull the TX Key Pin 2 input of microcontroller IC301 low. The microcontroller T/R output at Pin 11
then goes high to turn on Q202, which turns on pass transistor Q201 to apply +6VDC to the transmitter as
described previously. The transmitter can also be keyed through J301 with an audio accessory that
inserts a microphone and PTT switch in series to ground, drawing current through CR304.
+VTX Supply
With the transmitter enabled as described above, the +VTX voltage from Q201 is applied to transmitter
RF amplifier Q204. +VTX supply also forward biases the PIN switching diodes CR201 and CR101 as
previously described. The transmitter RF final amplifier Q203 is powered by the battery supply.
The Pin 11 T/R output of microcontroller IC301 can be PC programmed to hold the transmitter on after the
PTT switch has been released to allow tone related turn-off codes for squelch tail elimination.
Power Amplifier
Q204 and associated components amplify the VCO signal and apply it to the input of RF Final amplifier
module Q203 at Pin 1. The 50Ω output of Q203 is matched to the antenna switching circuitry and applied
to the antenna through the low-pass filter.
The RF power output is programmable by a licensed RF technician. The SST-444 can be programmed
on a channel-by-channel basis for low or high power operation. The power control digital Potentiometer
IC306B is used to adjust the Q203 gate voltage and set RF power output.
Voice / Tone Conditioning in Transmit Mode
SST-444 audio conditioning filter circuits are shared with the receiver. The same high-pass filter/amplifier
(IC303C and associated components) used in receive voice band conditioning is used in the transmitter
voice band. Similarly, the low-pass filter (IC308 and associated components) used for sub-audible tone
decode filtering is also used for tone encode. Altering circuit configuration with bilateral switches IC304A,
B and C permits the use of the same audio filtering system for both transmit and receive modes.
Voice Band
M301 microphone audio is passes through CR304, C334 and is switched by IC304A to the input of
IC303C, which along with its associated components form a high-pass filter/amplifier circuit that
attenuates audio signals below 300 Hz. The output of IC303C is applied to the input of IC305B limiting
amplifier. Bilateral switch IC304B switches R335 in parallel with R336, raising the gain of limiting amplifier
IC305B for full limiting of the transmitter voice audio. The output of IC305B is applied to the input of
IC303D, which along with its associated components form an 18 dB/octave low-pass filter for frequencies
above 3 KHz. The output of IC303D is applied to voice deviation control IC306F, which sets the level of
the processed transmitter audio applied to summing node amplifier IC303B used to modulate the VCO
and reference oscillator.
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29
SST-444 THEORY OF OPERATION
Sub-Audible
Microcontroller IC301 generates the sub-audible selective signaling encode waveforms at Pin 21 and
applies them to the input of buffer amplifier IC305A. The output of IC305A is applied to the input of IC308,
a 5-pole low-pass filter that attenuates frequencies above 250 Hz. C342 and C343 set the corner
frequency of the low-pass filter, with C342 switched in by Pin 7 of IC301 to lower the corner frequency for
lower tones. The output of IC308 is applied to tone deviation control IC306D, which sets the level of the
transmitter sub-audible encode tones applied to summing node amplifier IC303B used to modulate the
VCO and reference oscillator.
MICROCONTROLLER
The SST-444 handheld transceiver is electronically controlled by IC301, an 8-bit microcontroller. IC301
has four 8-bit A/D inputs for processing analog signals.
PIN DESCRIPTION
1 RESET is connected to the SST-444 +5V to start the radio in a known state on power up.
2 TX KEY input is pulled LOW when either the internal or external PTT switch is pressed to initiate
transmitter operation.
3 AUDIO GATE ENABLE controls analog switches IC304A, B and C to configure the shared audio
processing circuitry for receive operation when LOW, and for transmitter operation when HIGH.
4, 25 SERIAL DATA INPUT links the microcontroller to communications from an external data terminal
via J303 RING connection. This allows programming of the SST-444 EEPROM memory used to
store channel frequency and configuration information.
5 DATA output sends serial data to frequency synthesizer IC401 to program frequency information,
IC302 EEPROM memory, and to IC306 to set the digital potentiometers.
6 EECLOCK output sends serial data clock pulses to EEPROM IC302 when reading or writing.
7 LOW-PASS CUT-OFF output goes LOW to lower the cut-off frequency of IC308 when the radio is
on a channel programmed for a CTCSS tone below 150 Hz. This output is in a tri-state OPEN
condition for all other tones.
8 DIGITAL POT LATCH sends a single positive pulse after data has been sent to IC306 to latch the
new data and change the digital potentiometers to the new programmed settings.
9 LED output goes LOW when the radio is on channel 1 and is HIGH for all other channels.
10 +5V SW output goes HIGH at a programmable periodic rate to remove the +5VSW supply from
various circuits in the radio, thus conserving battery life. In normal transmit or receive mode this
output is LOW.
11 T/R SWITCH output is connected to the Synthesizer circuitry to shift the frequency of the VCO
oscillator used in both transmit and receive. The output is HIGH in transmit and LOW in receive.
T/R output is also used to switch supply voltage to the transmit and receive circuits.
12 CLOCK output sends serial data clock pulses to frequency synthesizer IC401 and digital
potentiometers IC306 when programming these devices.
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30
SST-444 THEORY OF OPERATION
PIN DESCRIPTION
13 +V SW output is HIGH when the radio is turned on, keeping pass transistor Q304 turned on via
Q303 to supply power to the radio.
14 GROUND
15 VREFH sets the upper reference level for the A/D and is connected to the regulated +5 VDC.
16 A/D input BATTERY is used to measure the battery voltage for low and dead battery detection.
This input also serves as the ON/VOL UP input, and is pulled LOW when SW301 is depressed to
turn on the radio and raise the receiver speaker audio level.
17 A/D input VOL DN/OFF is pulled LOW when SW302 is depressed to lower the receiver speaker
audio level and turn off the radio. This input also serves as CHANNEL input, and goes to 2.5
VDC when channel selector switch SW303 is pressed to change the radio to the next
programmed channel.
18 A/D input TONE DECODE accepts the received QC (CTCSS) and DQC (DCS) waveforms after
signal processing for decode analysis.
19 A/D input RSSI is used to measure the output voltage of the noise detector for squelch detection.
20 LATCH output goes LOW to allow serial data to frequency synthesizer IC401 and goes HIGH to
latch the data, allowing the synthesizer to execute the new frequency information.
21 TONE ENCODE outputs generate the QC (CTCSS) and DQC (DCS) encode waveforms for
signal processing prior to modulating the VCO in transmit mode.
22 AUDIO AMP ENABLE output goes HIGH to apply power to audio amp IC307 for receiver speaker
audio or radio alert tones.
23 BEEP output generate the radio alert tones heard in the speaker.
24, 26 UNUSED
27 REFERENCE OSCILLATOR INPUT has the 3.6 MHz reference signal from the synthesizer.
28 +5 VDC VDD supply voltage.
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31
SST-444 ALIGNMENT PROCEDURE
An authorized RF service technician must perform test and alignment of the SST-444. Do not attempt
service of the SST-444 if not completely familiar with the operation of frequency synthesized radio
operation. The SST-444 can operate in either Narrow Band (2.5 KHz deviation) or Wide Band (5 KHz
deviation) systems.
RECOMMENDED TEST EQUIPMENT
1) 0 to +15 VDC, 2A current-limited power supply 3) Oscilloscope (to 20 MHz)
2) RF Communications Test Set (to 470 MHz) with: 4) VTVM or DMM
- FM Deviation Meter
- RF Wattmeter 5) RITRON PC Programming Kit
- Frequency Counter (to 470 MHz)
- SINAD Measuring Device 6) RITRON SST-SRVBD Test Module
RADIO PREPARATION
1) Make sure the radio battery is fully charged.
2) Install the RITRON SST-SRVBD test assembly and serial programming cable as follows:
a) Remove the SST-444 antenna from the radio.
b) Plug the SST-SRVBD into the 2.5 mm and 3.5 mm jacks on top of the radio.
c) Screw the SST-SRVBD antenna nut fully into the SST-444 antenna connector.
d) Set the jumper on the SST-SRVBD assembly to the “UHF” position.
e) Connect the serial programming cable from the PC computer (with the RITRON PC programming
kit software installed) to the SST-SRVBD test assembly
3) Connect the FM communications test set to the BNC connector on the SST-SRVBD test assembly.
4) Turn on the radio to place it in operating mode.
5) From the PC Programmer on-screen menu, select “Tune Radio” to display the Alignment screen.
6) Set the RF Communications Test set to the Alignment Frequency indicated on the Alignment screen.
7) Press the appropriate “Select” button on the Alignment screen to make the following adjustments:
SELECT Alignment
Frequency Transmit frequency
Mod Bal Modulation balance
Tone QC/DQC tone encode deviation – wide band
QC/DQC tone encode deviation – narrow band
Voice Voice deviation with no tone – wide band
Voice deviation with no tone – narrow band
Voice deviation with tone – wide band
Voice deviation with tone – narrow band
Power Low transmitter power
High transmitter power
8) After you have completed alignment of the SST-444, turn the radio off. This will remove the test
frequencies and return to operation on the customer’s programmed frequencies.
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32
SST-444 ALIGNMENT PROCEDURE
REFERENCE FREQUENCY
1) Make sure that the unit has been switched on and is at room temperature (approximately +25° C)
2) Select “Frequency” from the PC Programmer “Alignment” screen.
3) Set the RF communications test set to the Alignment Frequency on the Alignment screen.
4) Press the “Tune” button on the Alignment screen to activate the transmitter.
5) Transmitter frequency error should be less than +/- 500 Hz.
6) If frequency adjustment is required, press the left arrow on the tuning bar to lower the frequency or the
right arrow to raise the frequency.
7) Press the “Save” button to store the new alignment setting or “Cancel” to leave setting unchanged.
MODULATION BALANCE
Transmitter modulation balance has been set at the factory and should not require adjustment.
1) Select “Mod Bal” from the PC Programmer “Alignment” screen.
2) Set the RF communications test set to the Alignment Frequency on the Alignment screen.
3) Press the “Tune” button on the Alignment screen to activate the transmitter.
4) Check the de-modulated waveform for a 20 Hz square wave.
5) If adjustment of the modulation balance is required, press the left arrow on the tuning bar to flatten the
top of the waveform or the right arrow to reduce overshoot.
6) Press the “Save” button to store the new alignment setting or “Cancel” to leave setting unchanged.
TRANSMITTER TONE DEVIATION
Transmitter tone deviation has been set at the factory and should not require adjustment.
1) Select “Tone” from the PC Programmer “Alignment” screen.
2) Set the RF communications test set to the transmit frequency on the screen.
3) Select either “Wide Band” or “Narrow Band” by pressing the desired option button.
4) Press the “Tune” button on the Alignment screen to activate the transmitter.
5) If adjustment of the tone deviation is required, press the left arrow on the tuning bar to lower deviation
or the right arrow to raise deviation.
6) Press the “Save” button to store the new alignment setting or “Cancel” to leave setting unchanged.
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33
SST-444 ALIGNMENT PROCEDURE
TRANSMITTER VOICE DEVIATION
Transmitter voice deviation has been set at the factory and should not require adjustment.
1) Select “Voice” from the PC Programmer “Alignment” screen.
2) Set the RF communications test set to the transmit frequency on the screen.
3) Select “Voice Only - Wide Band“, “Voice Only - Narrow Band”, “Voice & Tone – Wide Band”, or “Voice
& Tone – Narrow Band” by pressing the desired option button.
4) Press the “Tune” button on the Alignment screen to activate the transmitter.
5) If adjustment of the voice deviation is required, press the left arrow on the tuning bar to lower deviation
or the right arrow to raise deviation.
6) Press the “Save” button to store the new alignment setting or “Cancel” to leave setting unchanged.
TRANSMITTER POWER
Transmitter power has been set at the factory and should not require adjustment.
1) Select “Power” from the PC Programmer “Alignment” screen.
2) Set the RF communications test set to the transmit frequency on the screen.
3) Select “Low Power” or “High Power” by pressing the desired option button.
4) Press the “Tune” button on the Alignment screen to activate the transmitter.
5) If adjustment of the transmitter power is required, press the left arrow on the tuning bar to lower power
or the right arrow to raise power.
6) Press the “Save” button to store the new alignment setting or “Cancel” to leave setting unchanged.
RECEIVER SENSITIVITY AND SQUELCH
The SST-444 receiver is factory tuned for a frequency range of 460 - 470 MHz. The SST-444 receiver is
configured from the factory for Wide Band operation, with a Narrow Band Model available as an option.
The SST-444 receiver bandwidth is configured on a per radio basis, it cannot be switched on a per
channel basis.
The receiver may be tuned to any 10 MHz frequency band between 450-470 MHz.
1) Program the radio to a receive frequency in the middle of the desired 10 MHz band.
2) Set the RF communications test set generator to a frequency exactly 87.3 MHz below the
programmed receive frequency at a RF level of approximately –40 dB. Modulate the RF signal with a
1 KHz tone at 3 KHz deviation for wide band, 1.5 KHz deviation for low band.
3) Connect an 8-Ohm speaker to the 3.5mm audio jack on the SST-SRVBD test assembly.
4) Adjust L101 for the minimum received signal at this image frequency.
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34
SST-444 ALIGNMENT PROCEDURE
5) Set the RF Communications Test Set generator to the programmed receive frequency at a RF level of
–120 dB. Modulate the RF signal with a 1 KHz tone at 3 KHz deviation for wide band, 1.5 KHz
deviation for low band.
6) Adjust L103 and L104 for the best receiver SINAD as measured across the 8-Ohm speaker.
7) Check receiver sensitivity at the lowest and highest operating frequencies and make slight adjustment
to L103 and L104 to balance between the two, if necessary.
RECEIVER NOISE SQUELCH
The noise squelch sensitivity is set at the factory for a 12dB SINAD signal. Using the PC Programmer,
squelch sensitivity can be adjusted on a per channel basis by adjusting the “Squelch Tightener” number to
between 0-7. The higher number will require a stronger received signal to open squelch.
1) Select “Channel” from the PC Programmer “Edit” menu on the main screen.
2) Select the channel to be set and press “Edit” button.
3) Set the RF communications test set to the transmit frequency on the screen.
4) Enter a Squelch Tightener number between 0-7.
5) Press the “OK” button on the Channel Edit screen to return to the Channel List screen.
6) Select any other channels to be set.
7) Press the “OK” button on the Channel List screen to return to the Main screen.
8) Select “Program Radio” from the PC Programmer “Radio” menu to save all setting changes.
SYNTHESIZER
The synthesizer is preset at the factory for operation between 460 and 470 MHz. There is no manual
adjustment to center the control voltage, with all adjustment performed by the factory selection of fixed
capacitor C413. Do not attempt to adjust the synthesizer control unless a key component in the
synthesizer has been replaced. Key components do not include the Y302 reference frequency TCVCXO
or IC401 synthesizer IC. Synthesizer alignment errors cause poor operation at temperature extremes.
Should adjustment of the VCO control voltage be necessary, the radio must first be disassembled and
powered up at 7.5 VDC. The following procedure defines testing of the VCO control voltage:
1) Select the channel that has the lowest receive frequency.
2) Connect a VTVM, DVM or oscilloscope to Test Point 1 and measure the VCO control voltage. This
voltage should be no less than 1.5 VDC.
3) Select the channel that has the highest receive frequency and measure Test Point 1. The control
voltage should be no higher than 4.5 VDC.
4) a) If adjustment of the VCO control voltage is required, remove the synthesizer shield top.
b) Replace C413 with a capacitor value that allows VCO control voltages between 1.5 and 4.5 VDC
for the operating frequencies desired. Decreasing the value of C413 will raise the operating
frequency of the VCO while increasing the value will lower the VCO frequency.
c) Replace the top of the synthesizer shield.
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35
SST-444 VOLTAGE CHART
Measurement Conditions
Supply voltage at 7.5 VDC, radio in operating mode, volume control at minimum, power strobe enabled,
transmitter set for full power.
IMPORTANT: Because the SST-444 portable is constructed with grounding sub-planes, use a system
ground in the same proximity as the circuit being measured. All readings indicated as GND are true
system ground.
KEY: All measurements are in VDC unless indicated otherwise.
NC = No connection
GND = Ground
* = Voltage is strobed in Power Saver mode
→= See note in right column
SST-444 VOLTAGES
DEVICE PIN Transmit Receive Standby DESCRIPTION
CR101 1 0.7 0.0 0.0 TX/RX switching
2NCNCNC
3 GND GND GND
CR102 1 GND GND GND Voltage clamp
2 GND GND GND
30.0 0.0 *
CR103 1 GND GND GND Noise detection
20.0 →*→ amplified receiver noise
30.0 < 0.5 *
CR201 1 1.4 0.0 0.0 TX/RX switching
2NCNCNC
3 0.7 0.0 0.0
CR301 C 7.5 7.5 7.5 Over voltage protection
A GND GND GND
CR302 C 7.5 7.5 7.5 Reverse voltage protection
A 2.2 4.8 4.8
CR303 1 6.8 6.8 6.8 Turn-on detection
2 4.2 4.2 4.2
3 6.1 6.1 6.1
CR304 1 2.0 4.7 4.7 PTT switching
2 2.2 4.7 4.7
3 2.4 5.0 5.0
CR305 1 GND GND GND Voltage clamp
2 5.0 5.0 5.0
3 0.0 0.0 0.0
CR306 1 2.4 2.4 2.4 Voltage clamp
2NCNCNC
3 2.4 2.4 2.4
CR307 C 7.5 7.5 7.5 Reverse voltage protection
A0.0 →*→ receive audio amp output
12
3
SOT-23
36
SST-444 VOLTAGE CHART
DEVICE PIN Transmit Receive Standby DESCRIPTION
CR401 1 5.0 5.0 * Biasing
24.8 4.8 *
3NCNCNC
CR402 1 GND GND GND VCO tuning
2NCNCNC
3→→ *→ 1.5 – 4.5 VDC VCO tuning voltage
CR403 1 GND GND GND VCO modulation
2NCNCNC
32.4 2.4 *
CR404 1 0.8 0.0 * TX/RX VCO switching
2NCNCNC
30.0 4.8 *
IC101 1 0.0 4.7 * RX FM-IF subsystem
2NCNCNC
30.0 3.8 *
40.0 4.7 *
50.0 3.8 *
60.0 3.8 *
70.0 3.8 *
80.0 4.7 *
90.0 2.0 *
10 0.0 0.6 *
11 0.0 2.4 *
12 0.0 0.0 *
13 NC NC NC
14 NC NC NC
15 GND GND GND
16 0.0 1.7 *
IC301 1 5.0 5.0 5.0 Microcontroller
2 0.0 5.0 5.0
3 5.0 0.0 0.0
4 0.0 0.0 0.0
5 0.0 0.0 0.0
6 0.0 0.0 0.0
7 0.0 0.0 0.0
8 0.0 0.0 0.0
9→→→→
0.0 VDC on Channel 1 else 5.0 VDC
10 0.0 0.0 *
11 5.0 0.0 0.0
12 5.0 5.0 *
13 5.0 5.0 5.0
14 GND GND GND
15 5.0 5.0 5.0
16 4.2 4.2 4.2
17 5.0 5.0 5.0
18 2.4 2.4 *
19 0.0 0.5 *
20 5.0 5.0 5.0
21 →2.4 * → 0-5 VDC tone encode waveform
22 0.0 5.0 0.0
23 0.0 0.0 0.0
24 NC NC NC
25 0.0 0.0 0.0
26 NC NC NC
27 →→→→
3.6 MHz clock signal
28 5.0 5.0 5.0
37
SST-444 VOLTAGE CHART
DEVICE PIN Transmit Receive Standby DESCRIPTION
IC302 1 GND GND GND EEPROM
2 GND GND GND
3 GND GND GND
4 GND GND GND
5 0.0 0.0 0.0
6 0.0 0.0 0.0
7 GND GND GND
8 5.0 5.0 5.0
IC303 1 2.4 2.4 * Audio processing
22.4 2.4 *
32.4 2.4 *
45.0 5.0 *
52.4 2.4 *
62.4 2.4 *
72.4 2.4 *
82.4 2.4 *
92.4 2.4 *
10 2.4 2.4 *
11 GND GND GND
12 2.4 2.4 *
13 2.4 2.4 *
14 2.4 2.4 *
IC304 1 0.0 0.0 * Audio signal switching
22.4 2.4 *
32.4 2.4 *
42.4 2.4 *
50.0 2.5 *
6 GND GND GND
7 GND GND GND
8 GND GND GND
9 5.0 0.0 0.0
10 5.0 0.0 0.0
11 5.0 0.0 0.0
12 2.4 2.4 *
13 NC NC NC
14 0.0 2.4 *
15 0.0 2.4 *
16 5.0 5.0 5.0
IC305 1 2.4 2.4 * Audio processing
22.4 2.4 *
32.4 2.4 *
4 GND GND GND
52.4 2.4 *
62.4 2.4 *
72.4 2.4 *
85.0 5.0 *
38
SST-444 VOLTAGE CHART
DEVICE PIN Transmit Receive Standby DESCRIPTION
IC306 1 2.0 2.0 * Audio signal level control
23.8 0.0 *
3 GND GND GND
40.0 2.5 *
52.4 2.4 *
62.4 2.4 *
72.4 2.4 *
80.0 0.0 *
95.0 5.0 *
10 GND GND GND
11 NC NC NC
12 0.0 0.0 *
13 2.4 2.4 *
14 2.4 2.4 *
15 2.4 2.4 *
16 2.4 2.4 *
17 2.4 2.4 *
18 4.0 4.0 *
19 5.0 5.0 *
20 5.0 5.0 *
IC307 1 NC NC NC Audio amplifier
2 0.0 0.0 0.0
3 GND GND GND
4 GND GND GND
5 0.0 3.7 0.0
6 0.0 7.5 0.0
7 0.0 3.7 0.0
8 NC NC NC
IC308 1 2.4 2.4 * Tone low pass filter
22.4 2.4 *
3 GND GND GND
45.0 5.0 *
52.4 2.4 *
62.4 2.4 *
75.0 5.0 *
83.2 3.2 *
IC309 1 7.5 7.5 7.5 +5 VDC voltage regulator
2 GND GND GND
3 7.5 7.5 7.5
4NCNCNC
5 5.0 5.0 5.0
39
SST-444 VOLTAGE CHART
DEVICE PIN Transmit Receive Standby DESCRIPTION
IC401 1 →→→→
3.6 MHz clock signal
2 5.0 5.0 * Frequency synthesizer
3NCNCNC
4NCNCNC
5 5.0 5.0 5.0
6→→ *→ 1.5 – 4.5 VDC VCO tuning voltage
7 GND GND GND
82.2 2.2 *
9NCNCNC
10 2.4 2.4 *
11 2.4 2.4 *
12 5.0 5.0 *
13 NC NC NC
14 5.0 5.0 5.0
15 0.0 0.0 *
16 NC NC NC
17 5.0 5.0 5.0
18 5.0 5.0 *
19 0.0 0.0 *
20 2.2 →2.2 →*→ 14.4 MHz reference signal
Q 101 1 5.0 4.3 * RX +V switching
25.0 5.0 *
30.0 4.7 *
Q 102 1 0.0 0.7 * RX RF amplifier
2 GND GND GND
30.0 3.0 *
Q 103 1 0.0 4.7 * RX mixer
20.0 0.0 *
30.0 1.8 *
Q 104 1 0.0 0.7 * RX IF amplifier
2 GND GND GND
30.0 1.2 *
Q 105 1 0.0 0.7 * RX 2nd LO multiplier/amp
2 GND GND GND
30.0 4.6 *
Q 201 1 6.8 7.5 7.5 TX +V switching
2 7.5 7.5 7.5
3 6.0 0.0 0.0
Q 202 1 5.0 0.0 0.0 TX +V switching
2 4.3 0.0 0.0
3 6.8 7.5 7.5
Q 203 1 0.0 0.0 0.0 TX RF final amplifier
2 3.8 0.0 0.0
3 7.5 7.5 7.5
4 0.0 0.0 0.0
5 GND GND GND
Q 204 1 0.9 0.0 0.0 TX RF driver amplifier
2 0.3 0.0 0.0
3 6.0 0.0 0.0
40
SST-444 VOLTAGE CHART
DEVICE PIN Transmit Receive Standby DESCRIPTION
Q 301 1 5.0 0.0 0.0 PTT detection
2 GND GND GND
3 0.0 5.0 5.0
Q 302 1 4.3 5.0 5.0 PTT detection
2 5.0 5.0 5.0
3 5.0 0.0 0.0
Q 303 1 5.0 5.0 5.0 Battery +V switching
2 4.3 4.3 4.3
3 6.8 6.8 6.8
Q 304 1 6.8 6.8 6.8 Battery +V switching
2 7.5 7.5 7.5
3 7.5 7.5 7.5
Q 306 1 4.3 4.3 5.0 +5V switching
2 5.0 5.0 5.0
35.0 5.0 *
Q 307 1 0.0 5.0 0.0 Audio amplifier enable
2 0.0 4.3 0.0
3 7.5 6.8 7.5
Q 308 1 7.5 6.8 7.5 Audio amplifier +V switching
2 7.5 7.5 7.5
3 0.0 7.5 0.0
Q 401 1 0.7 0.7 * VCO buffer amplifier
2 GND GND GND
32.9 2.9 *
Q 402 1 0.7 0.7 * VCO buffer amplifier
2 GND GND GND
32.8 2.8 *
Q 403 1 2.3 2.3 * VCO oscillator
21.6 1.6 *
34.3 4.3 *
Q 404 1 4.7 4.7 * VCO voltage de-coupling
24.3 4.3 *
35.0 5.0 *
Q 405 1 0.0 4.3 * TX/RX VCO switching
24.3 4.3 *
34.2 0.0 *
Q 406 1 0.0 4.3 * TX/RX VCO switching
2 GND GND GND
34.3 0.0 *
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41
SST-444 SCHEMATIC REFERENCE PARTS LIST
NOTE: This parts list reflects the most current component values. If a component value given in the
schematic differs from this list, the parts list should be considered the most current.
Last Update: June 13, 2000
Ref Ritron PN Description X Y Theta Loc
CAPACITORS
C101 151103A3 3.3pf NPO 0805 CHIP CAPACITOR 1065 3824 270 Top
C102 151102A2 2.2PF NPO 0805 50V CHIP CAP 949 3929 180 Top
C103 15110120 12PF NPO 0805 50V CHIP CAP 791 4059 90 Top
C104 15110220 22PF NPO 0805 50V CHIP CAP 909 3824 270 Top
C105 15110180 18PF NPO 0805 50V CHIP 1018 3608 270 Top
C106 15110180 18PF NPO 0805 50V CHIP 869 3716 180 Top
C107 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 734 3620 180 Top
C108 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 675 3519 90 Top
C109 151106A8 6.8PF NPO 0805 50V CHIP 637 3994 90 Top
C110 151103A9 3.9PF NPO 0805 50V CHIP 557 3993 270 Top
C111 151103A3 3.3pf NPO 0805 CHIP CAPACITOR 516 4099 180 Top
C112 151103A3 3.3pf NPO 0805 CHIP CAPACITOR 382 4099 180 Top
C113 15110100 10PF NPO 0805 50V CHIP CAP 476 3993 270 Top
C114 151108A2 8.2PF NPO 0805 50V CHIP 275 4059 270 Top
C115 15110150 15PF 0805 NPO 50V CHIP CAP 380 3786 0 Top
C116 15182103 .01uF CAPACITOR, CHIP, 0402,Z5U,5/10/20 276 3382 180 Top
C117 15110150 15PF 0805 NPO 50V CHIP CAP 199 3598 180 Top
C118 15110470 47PF NPO 0805 50V CHIP 160 3491 90 Top
C119 15181472 .0047uF CAPACITOR, CHIP, 0402, X7R,5/10% 485 3367 270 Top
C120 151108A2 8.2PF NPO 0805 50V CHIP 407 3548 0 Bottom
C121 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 138 947 90 Bottom
C122 152B6106 10uF 10V 3.4 X 2.8 CHIP TANTALUM 451 1669 0 Bottom
C123 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 450 946 90 Bottom
C124 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 349 884 0 Bottom
C125 15119104 .1uF X7R 0805 25V CERAMIC CHIP CAP 350 1364 0 Bottom
C126 15119104 .1uF X7R 0805 25V CERAMIC CHIP CAP 441 1557 0 Bottom
C127 15119104 .1uF X7R 0805 25V CERAMIC CHIP CAP 69 2203 0 Bottom
C128 15119104 .1uF X7R 0805 25V CERAMIC CHIP CAP 225 2114 270 Bottom
C129 15119104 .1uF X7R 0805 25V CERAMIC CHIP CAP 392 1802 0 Bottom
C130 15182103 .01uF CAPACITOR, CHIP, 0402,Z5U,5/10/20 571 904 90 Bottom
C131 15110330 33PF NPO 0805 50V CHIP 38 1263 0 Bottom
C132 15110330 33PF NPO 0805 50V CHIP 64 1156 270 Bottom
C133 15119104 .1uF X7R 0805 25V CERAMIC CHIP CAP 69 2100 0 Bottom
C134 15182103 .01uF CAPACITOR, CHIP, 0402,Z5U,5/10/20 39 1635 90 Top
C135 15110220 22PF NPO 0805 50V CHIP CAP 171 1533 180 Bottom
C201 15180101 100pF CAPACITOR, CHIP, 0402, COG, 5% 1302 3153 90 Bottom
C202 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 871 3384 270 Bottom
C203 15180101 100pF CAPACITOR, CHIP, 0402, COG, 5% 997 3248 90 Bottom
C204 152A8105 1MFD 16V ~3.2 X 1.6~ CHIP TANTALUM 1100 3496 270 Top
C205 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 1019 3494 90 Top
C206 15180101 100pF CAPACITOR, CHIP, 0402, COG, 5% 1748 3308 90 Bottom
C207 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 1748 3104 90 Bottom
C208 15110100 10PF NPO 0805 50V CHIP CAP 1796 2406 90 Top
C209 15119104 .1uF X7R 0805 25V CERAMIC CHIP CAP 1427 2284 90 Bottom
C210 15180101 100pF CAPACITOR, CHIP, 0402, COG, 5% 1492 2264 90 Bottom
C211 15110560 56PF NPO 0805 50V CHIP CAPACITOR 1715 2211 270 Top
C212 15110101 100PF NPO 0805 50V CHIP CAP 1788 3787 90 Top
C213 151103A9 3.9PF NPO 0805 50V CHIP 1682 3828 180 Top
C214 15110100 10PF NPO 0805 50V CHIP CAP 1652 4093 90 Top
C215 FACTORY SELECT 1439 4093 90 Top
C216 15110101 100PF NPO 0805 50V CHIP CAP 953 4136 90 Top
C217 151105A6 5.6PF NPO 0805 50V CHIP CAPACITOR 1035 4136 90 Top
C301 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 774 817 180 Bottom
![](/img.php?id=108261&img=bg2a.png)
42
SST-444 SCHEMATIC REFERENCE PARTS LIST
Ref Ritron PN Description X Y Theta Loc
C302 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 275 522 270 Top
C303 152B4226 22uF 6.3V 3.4 X 2.8 CHIP TANTALUM CAP 199 647 180 Top
C304 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 1261 4590 90 Bottom
C305 15180101 100pF CAPACITOR, CHIP, 0402, COG, 5% 1027 427 0 Top
C306 15180101 100pF CAPACITOR, CHIP, 0402, COG, 5% 613 402 270 Top
C307 15182103 .01uF CAPACITOR, CHIP, 0402,Z5U,5/10/20 20 4621 270 Top
C308 15111102 .001MF X7R 0805 50V CHIP CAP 0 0 0 Bottom
C309 15182103 .01uF CAPACITOR, CHIP, 0402,Z5U,5/10/20 496 1867 90 Bottom
C310 15119104 .1uF X7R 0805 25V CERAMIC CHIP CAP 1107 3264 0 Bottom
C311 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 1229 2967 90 Bottom
C312 15182103 .01uF CAPACITOR, CHIP, 0402,Z5U,5/10/20 544 4622 270 Top
C313 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 169 3033 270 Top
C314 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 1280 2568 180 Bottom
C315 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 1280 2271 180 Bottom
C316 15182103 .01uF CAPACITOR, CHIP, 0402,Z5U,5/10/20 826 2291 180 Top
C317 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 704 2321 0 Bottom
C318 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 826 2371 180 Top
C319 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 704 2407 0 Bottom
C320 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 1280 2410 180 Bottom
C321 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 1280 2488 180 Bottom
C322 15180101 100pF CAPACITOR, CHIP, 0402, COG, 5% 1280 2311 180 Bottom
C323 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 1280 2771 180 Bottom
C324 15119104 .1uF X7R 0805 25V CERAMIC CHIP CAP 969 2221 0 Top
C325 15180101 100pF CAPACITOR, CHIP, 0402, COG, 5% 1280 2687 180 Bottom
C326 15180101 100pF CAPACITOR, CHIP, 0402, COG, 5% 1280 2607 180 Bottom
C327 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 1280 2371 180 Bottom
C328 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 704 2446 0 Bottom
C329 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 638 2501 270 Bottom
C330 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 704 2571 0 Bottom
C331 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 704 2610 0 Bottom
C332 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 737 2672 270 Bottom
C333 152A6475 4.7UF 10V A-SIZE TANTALUM CHIP CAP 502 2703 180 Top
C334 15119104 .1uF X7R 0805 25V CERAMIC CHIP CAP 95 2765 180 Bottom
C335 15180101 100pF CAPACITOR, CHIP, 0402, COG, 5% 420 2842 270 Bottom
C336 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 454 3156 90 Bottom
C337 152B6106 10uF 10V 3.4 X 2.8 CHIP TANTALUM 724 3558 270 Bottom
C338 15180101 100pF CAPACITOR, CHIP, 0402, COG, 5% 254 3129 90 Top
C339 15119104 .1uF X7R 0805 25V CERAMIC CHIP CAP 245 2945 270 Top
C340 15111333 .033MFD X7R 0805 50V CHIP CAP 366 2665 270 Bottom
C341 15182103 .01uF CAPACITOR, CHIP, 0402,Z5U,5/10/20 585 2328 270 Bottom
C342 15110821 820PF NPO 0805 50V CHIP CAP 638 2964 180 Bottom
C343 15111122 .0012MF X7R 0805 50V CHIP 637 3045 180 Bottom
C344 15181472 .0047uF CAPACITOR, CHIP, 0402, X7R,5/10% 184 2436 0 Top
C345 15181472 .0047uF CAPACITOR, CHIP, 0402, X7R,5/10% 269 2436 0 Top
C346 152A8105 1MFD 16V ~3.2 X 1.6~ CHIP TANTALUM 614 2232 90 Top
C347 15180180 18pF CAPACITOR, CHIP, 0402, COG, 5% 286 2500 90 Top
C348 15119473 .047uF X7R 0805 25V CHIP CAPACITOR 474 2595 0 Top
C349 15111333 .033MFD X7R 0805 50V CHIP CAP 127 2621 90 Bottom
C350 15180101 100pF CAPACITOR, CHIP, 0402, COG, 5% 493 3156 90 Bottom
C351 15181222 .0022uF CAPACITOR, CHIP, 0402, X7R,5/10% 19 2670 180 Top
C352 15180100 10pF CAPACITOR, CHIP, 0402, COG, 5% 436 3228 90 Top
C353 15182103 .01uF CAPACITOR, CHIP, 0402,Z5U,5/10/20 593 3133 180 Top
C354 15180221 220pF CAPACITOR, CHIP, 0402, COG, 5% 379 2436 90 Bottom
C355 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 301 2435 90 Bottom
C356 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 258 2393 90 Bottom
C357 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 153 2415 180 Top
C358 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 585 2498 90 Bottom
C359 15180100 10pF CAPACITOR, CHIP, 0402, COG, 5% 490 2589 90 Bottom
C360 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 470 2270 270 Top
C361 15180101 100pF CAPACITOR, CHIP, 0402, COG, 5% 492 2074 0 Top
C362 15119104 .1uF X7R 0805 25V CERAMIC CHIP CAP 981 752 270 Bottom
![](/img.php?id=108261&img=bg2b.png)
43
SST-444 SCHEMATIC REFERENCE PARTS LIST
Ref Ritron PN Description X Y Theta Loc
C363 152B6106 10uF 10V 3.4 X 2.8 CHIP TANTALUM 1231 427 0 Top
C364 15119104 .1uF X7R 0805 25V CERAMIC CHIP CAP 1058 503 180 Bottom
C365 01503212 220MF 10V ELT CAPACITOR, 5mm HEIGHT 1491 5052 0.302 Top
C366 15119104 .1uF X7R 0805 25V CERAMIC CHIP CAP 1482 659 90 Bottom
C367 15119104 .1uF X7R 0805 25V CERAMIC CHIP CAP 1357 798 90 Bottom
C368 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 247 2708 270 Bottom
C369 15180101 100pF CAPACITOR, CHIP, 0402, COG, 5% 664 2454 90 Top
C401 15180101 100pF CAPACITOR, CHIP, 0402, COG, 5% 1566 1966 270 Top
C402 151101A5 1.5PF NPO 0805 50V CHIP 1640 194 90 Top
C403 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 1680 1828 90 Top
C404 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 1066 1850 180 Top
C405 15180101 100pF CAPACITOR, CHIP, 0402, COG, 5% 1353 2013 180 Top
C406 151101A5 1.5PF NPO 0805 50V CHIP 1182 1785 270 Top
C407 151104A7 4.7PF 0805 50V CHIP CAP. 1463 1604 0 Top
C408 151104A7 4.7PF 0805 50V CHIP CAP. 1572 1634 270 Top
C409 15119104 .1uF X7R 0805 25V CERAMIC CHIP CAP 980 1766 90 Top
C410 151104A7 4.7PF 0805 50V CHIP CAP. 1355 158 270 Top
C411 15180101 100pF CAPACITOR, CHIP, 0402, COG, 5% 1262 130 270 Top
C412 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 1047 1788 90 Top
C413 151101A8 1.8PF NPO 0805 50V CHIP 1462 1441 270 Top
C414 152B6106 10uF 10V 3.4 X 2.8 CHIP TANTALUM 722 1625 0 Top
C415 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 1535 969 270 Top
C416 15180101 100pF CAPACITOR, CHIP, 0402, COG, 5% 1731 1114 270 Top
C417 15180101 100pF CAPACITOR, CHIP, 0402, COG, 5% 1538 1356 90 Top
C418 15180101 100pF CAPACITOR, CHIP, 0402, COG, 5% 677 1121 180 Top
C419 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 678 1201 180 Top
C420 15181102 .001uF CAPACITOR, CHIP, 0402, X7R, 5/10% 678 1240 180 Top
C421 15180101 100pF CAPACITOR, CHIP, 0402, COG, 5% 1053 1576 180 Top
C422 15110100 10PF NPO 0805 50V CHIP CAP 1119 1512 180 Top
C423 151101A0 1.0PF NPO 0805 50V CHIP 1256 1400 0 Top
C424 151108A2 8.2PF NPO 0805 50V CHIP 1187 1252 270 Top
C425 15180101 100pF CAPACITOR, CHIP, 0402, COG, 5% 1069 937 90 Top
C426 15111222 .0022uF X7R 0805 50V CHIP CAPACITOR 832 922 180 Top
C427 152AB334 .33MF 35V ~3.2X1.6~ CHIP TANTALUM 812 1015 0 Top
C428 15180101 100pF CAPACITOR, CHIP, 0402, COG, 5% 855 1473 270 Top
C429 15111333 .033MFD X7R 0805 50V CHIP CAP 1029 1015 0 Top
C430 15180101 100pF CAPACITOR, CHIP, 0402, COG, 5% 971 1460 270 Top
C431 15182103 .01uF CAPACITOR, CHIP, 0402,Z5U,5/10/20 687 1393 180 Top
C432 15180101 100pF CAPACITOR, CHIP, 0402, COG, 5% 766 1100 180 Top
C433 15180101 100pF CAPACITOR, CHIP, 0402, COG, 5% 932 1460 90 Top
C434 15180101 100pF CAPACITOR, CHIP, 0402, COG, 5% 1101 1264 0 Top
C435 15180101 100pF CAPACITOR, CHIP, 0402, COG, 5% 687 1355 180 Top
DIODES
CR101 48D100A2 MA4CP101A PIN DIODE, SOT-23 1178 3820 90 Top
CR102 48E1005G MMBD-352LT1 SCHOTTKY DIODE SOT23 908 3608 270 Top
CR103 48A1005C MMBD7000, DUAL DIODES IN SERIES, SOT-23 356 2147 0 Bottom
CR201 48D100A2 MA4CP101A PIN DIODE, SOT-23 1302 3991 0 Top
CR301 48B61012 1N4742A ZENER DIODE, 12V 1W DL-41 MELF 991 604 90 Top
CR302 48AA01SA DIODE, 1A, 50V, SMT, D0214AC CASE 1154 630 90 Top
CR303 48A1005B MMBD6100, DUAL DIODES, COM CATHODE, SOT2 363 431 90 Top
CR304 48A100A3 MMBD2835, DUAL DIODES, COM ANODE, SOT-23 65 4089 0 Top
CR305 48A1005C MMBD7000, DUAL DIODES IN SERIES, SOT-23 626 2802 0 Bottom
CR306 48A1005C MMBD7000, DUAL DIODES IN SERIES, SOT-23 449 2956 90 Bottom
CR307 48AA01SA DIODE, 1A, 50V, SMT, D0214AC CASE 1290 630 90 Top
CR401 48A1005C MMBD7000, DUAL DIODES IN SERIES, SOT-23 695 1808 90 Top
CR402 48C1004E MMBV-105G DIODE VVC, SOT-23 1147 1115 180 Top
CR403 48C1004G MMBV-2101L DIODE VVC SOT-23 1119 1400 180 Top
CR404 48A1004D MMBV3401 PIN/UHF DIODE SOT-23 1552 1239 270 Top
![](/img.php?id=108261&img=bg2c.png)
44
SST-444 SCHEMATIC REFERENCE PARTS LIST
Ref Ritron PN Description X Y Theta Loc
FUSE
F301 06000040 WIRE; #40AWG TINNED BUS (INCHES) 754 603 270 Bottom
INTEGRATED CIRCUITS
IC101 31030003 MC3371D SUBSYSTEM IC, SO-16 314 1158 270 Bottom
IC301 314G0301 MCU, 28 PIN, SOIC, SST/JMX 4-SERIES v01 992 2546 0 Bottom
IC302 31210005 EEPROM, 512X8, 24C04 989 2501 180 Top
IC303 310K0004 LMV324MT RAIL TO RAIL QUAD OP AMP 474 2442 180 Top
IC304 311K0003 SWITCH,ANALOG,TRIPLE SPDT,4053,TSSOP-16 241 2683 0 Top
IC305 310K0003 LMV358MM DUAL OP AMP, GP LV R/R TSSOP 404 3120 0 Top
IC306 310K0001 DS1806E 6 PROG POTS 10K OHM 20-PIN TSSOP 242 2185 0 Top
IC307 31010004 LM386MX-1 AUDIO AMP SO-8 1331 567 90 Bottom
IC308 310K0002 MAX7410 5TH ORDER SW CAP BUTTERWORTH LPF 407 2935 0 Top
IC309 310E0002 REGULATOR,LDO,LP2980,5V,W ENABLE,SOT-25 162 504 0 Top
IC401 313K0004 SYNTHESIZER TSSOP MC145192 891 1265 180 Top
JACKS
J301 02100001 2.5MM PC-MT JACK; ANT-CHGR 1178 4668 0 Top
J303 02100053 3.5MM STEREO JACK; PANEL MOUNT 1560 4646 0 Top
INDUCTORS
L101 01850201 1.5T SW COIL W/5MM SHIELD & ALUM CORE 721 4291 90 Top
L102 18110151 CHIP INDUCTOR .15uhy 629 3722 270 Top
L103 01850201 1.5T SW COIL W/5MM SHIELD & ALUM CORE 484 4291 270 Top
L104 01850201 1.5T SW COIL W/5MM SHIELD & ALUM CORE 204 4292 270 Top
L105 18433103 3T AIRCOIL, SMT, 8.0nH, .120 X .145 332 3901 180 Top
L106 18110102 CHIP INDUCTOR 1.0uhy 280 3474 0 Top
L107 18433101 1T AIRCOIL, SMT 2.5nH, .120 X .145 480 3492 180 Top
L108 18110681 CHIP INDUCTOR .68uhy 51 1648 180 Bottom
L201 18414104 4.5T AIRCOIL #24AWG .0625” ID RHH SMT 929 3459 270 Top
L202 18110150 INDUCTOR, CHIP, 15nH 1454 2281 180 Top
L203 18414104 4.5T AIRCOIL #24AWG .0625"ID RHH SMT 1695 3948 90 Top
L204 18414104 4.5T AIRCOIL #24AWG .0625"ID RHH SMT 1479 3945 180 Top
L205 18110102 CHIP INDUCTOR 1.0uhy 1230 3667 0 Top
L206 18414105 5.5T AIRCOIL #24AWG .0625"ID RHH SMT 1093 3979 90 Top
L207 18433102 2T AIRCOIL SMT 5.0nH .120 X .145 932 4343 0 Top
L401 18433209 9T AIRCOIL, SMT, 9.85 nH, .159 X .056 1376 1418 270 Top
L402 18414109 9.5T AIRCOIL #24AWG .0625"ID RHH SMT 1352 118 0 Top
L403 18110820 INDUCTOR, CHIP 82nH 1548 109 270 Top
L404 18110101 CHIP INDUCTOR 0.1uhy 1187 966 270 Top
L405 18110101 CHIP INDUCTOR 0.1uhy 753 1485 0 Top
MICROPHONE
M301 05500037 MICROPHONE; ELECTRET, MINIATURE 0 0 0 Bottom
CONNECTORS
P201 25500700 CONTACT, PCB MNT, ANTENNA,SST 896 4550 90 Top
P302 21310021 HEADER, 2 PIN SIDE ENTRY SHROUDED 754 737 0 Top
TRANSISTORS
Q101 4801002A MMBT3906 PNP, SOT23 675 3405 270 Top
Q102 482100V0 TRANSISTOR, NPN, UHF, SOT-23, PBR-941 734 3828 0 Top
Q103 4841006U MMBFJ309LT1, N-CHAN, RF, SOT23 340 3639 270 Top
Q104 4821003B MMBT918LT1 VHF SOT23 (3B) 270 3548 0 Bottom
![](/img.php?id=108261&img=bg2d.png)
45
SST-444 SCHEMATIC REFERENCE PARTS LIST
Ref Ritron PN Description X Y Theta Loc
Q105 4821003B MMBT918LT1 VHF SOT23 (3B) 38 1374 180 Bottom
Q201 4801002A MMBT3906 PNP, SOT23 908 3268 90 Bottom
Q202 4801001Q MMBT5088 NPN, SOT-23 766 3268 270 Bottom
Q203 04801503 M68710H 2W RF MODULE 450-470 MHz 6.0V 1819 2710 90 Top
Q204 482100V0 TRANSISTOR, NPN, UHF, SOT-23, PBR-941 1603 2274 270 Top
Q301 48010R02 MUN2211T1, NPN, INT 10K/10K BIAS, "8A", 1133 2987 90 Bottom
Q302 4801002A MMBT3906 PNP, SOT23 1094 3124 90 Bottom
Q303 4801001Q MMBT5088 NPN, SOT-23 583 519 0 Top
Q304 480100DH BCW68GLT1 .8AMP PNP SOT-23 445 668 0 Top
Q306 4801002A MMBT3906 PNP, SOT23 1222 2259 90 Top
Q307 4801001Q MMBT5088 NPN, SOT-23 964 615 0 Bottom
Q308 480100DH BCW68GLT1 .8AMP PNP SOT-23 1162 712 0 Bottom
Q401 482100V0 TRANSISTOR, NPN, UHF, SOT-23, PBR-941 1470 1919 270 Top
Q402 482100V0 TRANSISTOR, NPN, UHF, SOT-23, PBR-941 1289 1920 270 Top
Q403 482100V0 TRANSISTOR, NPN, UHF, SOT-23, PBR-941 1460 1714 270 Top
Q404 4801001Q MMBT5088 NPN, SOT-23 837 1766 270 Top
Q405 4801006A MUN2111T1, PNP, INT 10K/10K BIAS, SC-59 1634 1376 270 Top
Q406 48010R02 MUN2211T1, NPN, INT 10K/10K BIAS, "8A", 1691 1234 0 Top
RESISTORS
R101 47180103 10K OHM, RESISTOR, CHIP, 0402,1/16W,5% 579 3344 90 Top
R102 47180103 10K OHM, RESISTOR, CHIP, 0402,1/16W,5% 734 3581 180 Top
R103 47180102 1K OHM RESISTOR, CHIP,0402, 1/16W,5% 774 3716 270 Top
R104 47180392 3.9K OHM RESISTOR, CHIP, 0402, 1/16W, 5% 829 3810 270 Top
R105 47180561 560 OHM RESISTOR, CHIP, 0402, 1/16W, 5% 714 3519 270 Top
R106 47180152 1.5K OHM RESISTOR, CHIP, 0402, 1/16W,5% 475 3610 270 Top
R107 47180152 1.5K OHM RESISTOR, CHIP, 0402, 1/16W,5% 388 3484 180 Bottom
R108 47180223 22K OHM RESISTOR, CHIP, 0402, 1/16W, 5% 251 3450 180 Bottom
R109 47180101 100 OHM RESISTOR, CHIP, 0402,1/16W,5% 167 3450 180 Bottom
R110 47180154 150K OHM RESISTOR, CHIP, 0402, 1/16W,5% 411 946 270 Bottom
R111 47180122 1.2K OHM RESISTOR, CHIP, 0402, 1/16W,5% 529 904 270 Bottom
R112 47180224 220K OHM RESISTOR, CHIP, 0402, 1/16W, 5% 349 966 180 Bottom
R113 47180123 12K OHM RESISTOR, CHIP, 0402, 1/16W,5% 489 946 90 Bottom
R114 47180152 1.5K OHM RESISTOR, CHIP, 0402, 1/16W,5% 551 966 0 Bottom
R115 47180104 100K OHM, RESISTOR, CHIP, 0402,1/16W,5% 161 2174 270 Bottom
R116 47180103 10K OHM, RESISTOR, CHIP, 0402,1/16W,5% 161 2089 90 Bottom
R117 47180393 39K OHM RESISTOR, CHIP, 0402, 1/16W, 5% 117 1676 90 Top
R118 47180103 10K OHM, RESISTOR, CHIP, 0402,1/16W,5% 79 1533 90 Bottom
R119 47180102 1K OHM RESISTOR, CHIP,0402, 1/16W,5% 59 1470 180 Bottom
R120 47180681 680 OHM RESISTOR, CHIP, 0402, 1/16W, 5% 78 1635 90 Top
R201 47180103 10K OHM, RESISTOR, CHIP, 0402,1/16W,5% 790 3384 90 Bottom
R202 47180471 470 OHM RESISTOR, CHIP, 0402, 1/6W, 5% 669 3248 270 Bottom
R203 47180181 180 OHM RESISTOR, CHIP, 0402, 1/16W, 5% 908 3151 90 Bottom
R204 47100270 27 OHM 0805 CHIP RESISTOR 1796 2211 270 Top
R205 47180822 8.2K OHM RESISTOR, CHIP, 0402, 1/16W, 5% 1555 2244 0 Bottom
R206 47180182 1.8K OHM RESISTOR, CHIP, 0402, 1/16W,5% 1618 2264 270 Bottom
R207 47180181 180 OHM RESISTOR, CHIP, 0402, 1/16W, 5% 1184 3549 270 Top
R208 47180102 1K OHM RESISTOR, CHIP,0402, 1/16W,5% 879 4148 90 Top
R301 47180103 10K OHM, RESISTOR, CHIP, 0402,1/16W,5% 536 686 90 Top
R302 47100471 470 OHM 0805 CHIP RES. 475 479 270 Top
R303 47180104 100K OHM, RESISTOR, CHIP, 0402,1/16W,5% 325 546 90 Top
R304 47180102 1K OHM RESISTOR, CHIP,0402, 1/16W,5% 623 639 270 Top
R305 47180104 100K OHM, RESISTOR, CHIP, 0402,1/16W,5% 402 547 270 Top
R306 47180103 10K OHM, RESISTOR, CHIP, 0402,1/16W,5% 535 1867 90 Bottom
R307 47180103 10K OHM, RESISTOR, CHIP, 0402,1/16W,5% 995 3143 90 Bottom
R308 47180103 10K OHM, RESISTOR, CHIP, 0402,1/16W,5% 1127 3328 180 Bottom
R309 47180103 10K OHM, RESISTOR, CHIP, 0402,1/16W,5% 1257 2891 270 Bottom
R310 47180104 100K OHM, RESISTOR, CHIP, 0402,1/16W,5% 704 2191 0 Bottom
R311 47180104 100K OHM, RESISTOR, CHIP, 0402,1/16W,5% 504 4622 270 Top
R312 47180103 10K OHM, RESISTOR, CHIP, 0402,1/16W,5% 704 2230 0 Bottom
![](/img.php?id=108261&img=bg2e.png)
46
SST-444 SCHEMATIC REFERENCE PARTS LIST
Ref Ritron PN Description X Y Theta Loc
R313 47180104 100K OHM, RESISTOR, CHIP, 0402,1/16W,5% 1184 2376 270 Top
R314 47180472 4.7K OHM RESISTOR, CHIP, 0402, 1/16W, 5% 1260 2375 270 Top
R315 47180102 1K OHM RESISTOR, CHIP,0402, 1/16W,5% 738 2841 90 Bottom
R316 47180103 10K OHM, RESISTOR, CHIP, 0402,1/16W,5% 761 2557 90 Top
R317 47180103 10K OHM, RESISTOR, CHIP, 0402,1/16W,5% 800 2506 90 Top
R318 47180104 100K OHM, RESISTOR, CHIP, 0402,1/16W,5% 704 2521 180 Bottom
R319 47180471 470 OHM RESISTOR, CHIP, 0402, 1/6W, 5% 737 2756 270 Bottom
R320 47180471 470 OHM RESISTOR, CHIP, 0402, 1/6W, 5% 698 2879 270 Bottom
R321 47180103 10K OHM, RESISTOR, CHIP, 0402,1/16W,5% 636 2899 0 Bottom
R322 47180393 39K OHM RESISTOR, CHIP, 0402, 1/16W, 5% 294 3070 270 Bottom
R323 47180823 82K OHM RESISTOR, CHIP, 0402, 1/16W, 5% 371 3070 270 Bottom
R324 47180224 220K OHM RESISTOR, CHIP, 0402, 1/16W, 5% 332 3070 270 Bottom
R325 47180104 100K OHM, RESISTOR, CHIP, 0402,1/16W,5% 416 3156 90 Bottom
R326 47180183 18K OHM RESISTOR, CHIP, 0402, 1/16W, 5% 585 2413 270 Bottom
R327 47180183 18K OHM RESISTOR, CHIP, 0402, 1/16W, 5% 624 2328 90 Bottom
R328 47180103 10K OHM, RESISTOR, CHIP, 0402,1/16W,5% 493 2774 270 Bottom
R329 47180153 15K OHM RESISTOR, CHIP, 0402, 1/16W,5% 168 2374 90 Top
R330 47180100 10 OHM RESISTOR, CHIP,0402, 1/16W 5% 664 2369 90 Top
R331 47180104 100K OHM, RESISTOR, CHIP, 0402,1/16W,5% 269 2396 0 Top
R332 47180154 150K OHM RESISTOR, CHIP, 0402, 1/16W,5% 207 2501 90 Top
R333 47180473 47K OHM RESISTOR, CHIP, 0402, 1/16W, 5% 246 2500 90 Top
R334 47180273 27K OHM RESISTOR, CHIP, 0402, 1/16W, 5% 566 2588 90 Top
R335 47180102 1K OHM RESISTOR, CHIP,0402, 1/16W,5% 60 2787 270 Top
R336 47180104 100K OHM, RESISTOR, CHIP, 0402,1/16W,5% 23 2787 270 Top
R337 47180103 10K OHM, RESISTOR, CHIP, 0402,1/16W,5% 532 3156 270 Bottom
R338 47180224 220K OHM RESISTOR, CHIP, 0402, 1/16W, 5% 397 3228 90 Top
R339 47180394 390K OHM RESISTOR, CHIP, 0402, 1/6W, 5% 420 2347 270 Bottom
R340 47180104 100K OHM, RESISTOR, CHIP, 0402,1/16W,5% 340 2436 90 Bottom
R341 47180104 100K OHM, RESISTOR, CHIP, 0402,1/16W,5% 239 2455 0 Bottom
R342 47180184 180K OHM RESISTOR, CHIP, 0402, 1/16W, 5% 153 2376 180 Bottom
R343 47180473 47K OHM RESISTOR, CHIP, 0402, 1/16W, 5% 731 3133 0 Bottom
R344 47180104 100K OHM, RESISTOR, CHIP, 0402,1/16W,5% 67 2416 180 Bottom
R345 47180104 100K OHM, RESISTOR, CHIP, 0402,1/16W,5% 153 2455 180 Bottom
R346 47180102 1K OHM RESISTOR, CHIP,0402, 1/16W,5% 732 3094 180 Top
R347 47180274 270K OHM RESISTOR, CHIP, 0402, 1/16W, 5% 568 2588 90 Bottom
R348 47180473 47K OHM RESISTOR, CHIP, 0402, 1/16W, 5% 529 2589 90 Bottom
R349 47180823 82K OHM RESISTOR, CHIP, 0402, 1/16W, 5% 29 2146 0 Top
R350 47180564 560K OHM RESISTOR, CHIP, 0402, 1/16W, 5% 29 2198 0 Top
R351 47180222 2.2K OHM RESISTOR, CHIP, 0402, 1/16W, 5% 431 2269 90 Top
R352 47100475 4.7M OHM 0805 CHIP RESISTOR 44 2406 0 Top
R353 47180103 10K OHM, RESISTOR, CHIP, 0402,1/16W,5% 453 2158 180 Top
R354 47180102 1K OHM RESISTOR, CHIP,0402, 1/16W,5% 847 653 180 Bottom
R355 47180103 10K OHM, RESISTOR, CHIP, 0402,1/16W,5% 912 772 90 Bottom
R356 47180273 27K OHM RESISTOR, CHIP, 0402, 1/16W, 5% 1293 780 90 Bottom
R357 47180102 1K OHM RESISTOR, CHIP,0402, 1/16W,5% 1147 534 90 Bottom
R358 47180153 15K OHM RESISTOR, CHIP, 0402, 1/16W,5% 1187 534 90 Bottom
R359 47180100 10 OHM RESISTOR, CHIP,0402, 1/16W 5% 1482 773 270 Bottom
R401 47180221 220 OHM RESISTOR, CHIP, 0402, 1/16W, 5% 1517 2006 90 Top
R402 47180101 100 OHM RESISTOR, CHIP, 0402,1/16W,5% 1640 1828 270 Top
R403 47180272 2.7K OHM RESISTOR, CHIP, 0402, 1/16W, 5% 1450 2013 180 Top
R404 47180102 1K OHM RESISTOR, CHIP,0402, 1/16W,5% 1452 1825 180 Top
R405 47180101 100 OHM RESISTOR, CHIP, 0402,1/16W,5% 1153 1900 270 Top
R406 47180272 2.7K OHM RESISTOR, CHIP, 0402, 1/16W, 5% 1193 1900 270 Top
R407 47180470 47 OHM RESISTOR, CHIP, 0402, 1/16W, 5% 1086 1788 270 Top
R408 47180470 47 OHM RESISTOR, CHIP, 0402, 1/16W, 5% 1067 1726 180 Top
R409 47180271 270 OHM RESISTOR, CHIP, 0402, 1/16W, 5% 1636 1655 90 Top
R410 47180153 15K OHM RESISTOR, CHIP, 0402, 1/16W,5% 1266 162 5180 Top
R411 47180153 15K OHM RESISTOR, CHIP, 0402, 1/16W,5% 1363 1694 270 Top
R412 47180102 1K OHM RESISTOR, CHIP,0402, 1/16W,5% 1271 1827 180 Top
R413 47180472 4.7K OHM RESISTOR, CHIP, 0402, 1/16W, 5% 677 1903 0 Top
R414 47180103 10K OHM, RESISTOR, CHIP, 0402,1/16W,5% 1634 1531 270 Top
![](/img.php?id=108261&img=bg2f.png)
47
SST-444 SCHEMATIC REFERENCE PARTS LIST
Ref Ritron PN Description X Y Theta Loc
R415 47180102 1K OHM RESISTOR, CHIP,0402, 1/16W,5% 1641 1068 90 Top
R416 47180104 100K OHM, RESISTOR, CHIP, 0402,1/16W,5% 1138 1576 0 Top
R417 47180102 1K OHM RESISTOR, CHIP,0402, 1/16W,5% 938 937 90 Top
R418 47180473 47K OHM RESISTOR, CHIP, 0402, 1/16W, 5% 938 1022 90 Top
R419 47180822 8.2K OHM RESISTOR, CHIP, 0402, 1/16W, 5% 718 906 0 Top
R420 47180103 10K OHM, RESISTOR, CHIP, 0402,1/16W,5% 718 946 180 Top
R421 47180223 22K OHM RESISTOR, CHIP, 0402, 1/16W, 5% 1101 1303 0 Top
R422 47180100 10 OHM RESISTOR, CHIP,0402, 1/16W 5% 894 1461 90 Top
R423 47180474 470K OHM RESISTOR, 0402, 1/16W, 5% 850 1100 180 Top
SPEAKER
SP301 05500045 SPEAKER, 45MM, 1W, LOW PROFILE SST/RTX 0 0 0 Bottom
SWITCHES
SW301 05100042 SWITCH SPST MOMENTARY MINI PC 260GM 268 4587 180 Top
SW302 05100042 SWITCH SPST MOMENTARY MINI PC 260GM 788 4588 180 Top
SW303 05100046 SWITCH, TACT LO PROFILE RT ANGLE 160gf 82 3097 270 Top
SW304 05100046 SWITCH, TACT LO PROFILE RT ANGLE 160gf 82 3948 270 Top
TRANSFORMER
T101 05600018 455KHZ IF TRANSFORMER (5MM) 128 1822 180 Top
CRYSTAL
Y302 23050003 TCVCXO, 14.400 MHz, 1.5 PPM, VC=30 PPM/V 146 837 90 Top
FILTERS
YF101 02301403 43.650 MHz Crystal Filter +/-6.0KHz UM-1 44 3524 90 Top
YF102 02301013 FILTER,CERAMIC,450KHz,+/-7.5KHz,6 POLE 249 1614 90 Top
HARDWARE
1750240B PCB, ML4 FR4 5UPM, .062 MIX, SST-444
25602500 CRYSTAL SUPPORT, RUBBER PAD, SMALL/UM-1
06001021 #28 AWG STRANDED WIRE; RED (INCHES)
06001023 #28 AWG STRANDED WIRE;GREEN INCHES
06001026 #28 AWG STRANDED WIRE; BLACK INCHES
06001029 #28 AWG STRANDED WIRE; BLUE INCHES
25105500 SHIELD, SST-PLUS SYNTHESIZER
25603000 FOAM, MOUNTING, SPEAKER,SST
25603900 SPACER, MIC FOAM, SST
25605700 MICROPHONE HOLDER, SST-PLUS
25900700 ADHESIVE, MTG, MIC HOLDER
26200800 HEATSINK, TOP, SST+
26200900 HEATSINK, BOTTOM, SST+
2811H401 SCREW #4-40 X .25 LG TRIM HEAD PHILLIPS
![](/img.php?id=108261&img=bg30.png)
48
SST-444 CASE ASSEMBLY PARTS LIST
Ref Ritron PN Description
MAIN CASE ASSEMBLY
13250000 CASE W/INSERT, PLASTIC, SST BLACK
13578000 DOOR, BATTERY, PLASTIC, SST 2-PC
13588000 LATCH, BATTERY DOOR, PLASTIC SST 2-PC
25106400 BATTERY DOOR HINGE RETAINER
25201500 RETAINER, PLASTIC, PTT, SST
25400600 BUSHING, THREADED, PLATED, ANTENNA SS
25603300 GRILLE CLOTH, SPEAKER, SST
25603400 DUAL JACK PLUG, RUBBER,SST
25606200 HINGE, BATTERY DOOR, SST
25800500 ACTUATOR, RUBBER,PTT,SST
25800600 ACTUATOR, RUBBER, TACT, SST
02802026 NUT; KNURLED; M4PO.5;/2.5MM JACK
02802027 NUT; KNURLED; M6PO.5/3.5MM JACK
28112401 SCREW 4-40 X 1/4" PHFLST
28233G03 KNURLED NUT, ANTENNA, JMX
CASE BOTTOM ASSEMBLY
13564000 CASE, BOTTOM, PLASTIC, SST 2-PC
2142D021 CONNECTOR, CABLE ASSEMBLY, 2-POS, SST+
25400800 SPRING CONTACT, BATTERY, SST W/O TABSC
25400900 CONTACT BATTERY SST-PLUS (POLARIZED)
25604800 SPACER, PCB, FOAM, SST 2-PC
CASE LABELS
14220001 LABEL, CONTROLS, SST
14222029 LABEL, NAMEPLATE, SST
14290002 BLANK LABEL, .75" X .25" GLOSSY WHITE +
14200037 LABEL SST/JMX MFG DATE CODE
14200039 LABEL FCC SERIAL SST-450
BELT CLIP
25201600 BELT CLIP, PLASTIC, SST BLACK
2811B600 SCREW 6-32 X 1/4" PHTRST
BATTERY PACK AND INSULATOR
BPS-6N-SC BATTERY,RECHG,7.2V NiCd,BLUE ,SST
14230088 LABEL, BATTERY, BPS-6N-SC, SST
25300600 INSULATOR, BATTERY, FIBRE, SST
25606000 FOAM SUPPORT, BATTERY JMX SERIES
25601600 BATTERY SHIM; ASSEMBLY ~X~ SERIES
ANTENNA
AFS-450 ANTENNA UHF MOLDED, 450-470 REG LEN SST
PACKING MATERIALS
14210004 LOW BATTERY NOTICE LABEL
14312006 SHIPPING CARTON, CARDBOARD,SST
14321002 FOAM INSERT, PACKING, SST/MINI
14500008 MANUAL, OWNERS, JMX/SST
14500016 USER MANUAL SST-444
14540006 WARRANTY REGISTRATION CARD