Patriot RITRON SST-442 Скачать руководство пользователя страница 21

THEORY OF OPERATION

SST-442

18

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-442 is serial programmed to set the
squelch threshold and hysteresis.

Voice / Tone Conditioning in Receive Mode

SST-442 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.

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 24 of microcontroller
IC301 are applied to the Pin 6 input of IC305B to
provide the SST-442 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 8

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.

Содержание RITRON SST-442

Страница 1: ...ical 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 instru...

Страница 2: ...D PROGRAMMABLE HANDHELD RADIO MAINTENANCE REPAIR OPERATING MANUAL FOR USE BY AUTHORIZED SERVICE MAINTENANCE PERSONNEL ONLY SST 442 MRM REV A COPYRIGHT 2001 RITRON INC ALL RIGHTS RESERVED RITRON JOBCOM...

Страница 3: ...g Frequency Table 13 Table 2 Quiet Call Codes and Frequencies 13 COMPUTER SOFTWARE COPYRIGHTS 13 PC COMPUTER PROGRAMMING 13 Programmable Features 14 Description of Features 15 TOPIC PAGE THEORY OF OPE...

Страница 4: ...ng 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 nu...

Страница 5: ...et Also provides cable connection for PC programming Microphone PTT 2 5 mm for external Chg Jack speaker microphone headset or RITRON model BC A wall charger CONTROLS Push Button Controls On Volume Up...

Страница 6: ...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 BATTERY Battery Pack 7 2 VDC 800 mAH rec...

Страница 7: ...propriate methods Safety Standards In 1991 the Institute of Electrical and Electronics Engineers IEEE and in 1992 the American National Standards Institute ANSI updated the 1982 ANSI standard for safe...

Страница 8: ...apacity 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...

Страница 9: ...may never fully discharge the battery pack during normal use Achieve maximum battery life by fully discharging the battery periodically to condition it After exposing the battery pack to many cycles...

Страница 10: ...y 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...

Страница 11: ...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 Monitor To monitor the channel press one...

Страница 12: ...ort 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 o...

Страница 13: ...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 ho...

Страница 14: ...it 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 See CHANNEL READ...

Страница 15: ...rect digit Turn the radio off check the digits you are attempting to enter then start over again 4 If you make a PTT click error turn the radio off then on and start over 5 If the radio does not emit...

Страница 16: ...ter with Windows 95 or later The computer must have an RS 232 serial port and a minimum of 2MB available on the hard disk drive for installation COMPUTER SOFTWARE COPYRIGHTS The RITRON Inc products de...

Страница 17: ...xed beep volume or for a beep volume that is adjusted with the Volume controls If fixed beep volume is selected the fixed level can be set between 0 100 Busy Channel Transmit Inhibit This keeps the ra...

Страница 18: ...g 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 sque...

Страница 19: ...cycle time is programmable using the PC Programming Kit The 5V SW power strobe output at Pin 10 of IC301 controls Q306 which switches the regulated 5 VDC to the audio processing circuitry and the synt...

Страница 20: ...06E 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...

Страница 21: ...rcuit 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 th...

Страница 22: ...rogrammed 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 Q203 Q204 and associated components amplif...

Страница 23: ...ncy 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 C...

Страница 24: ...s 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 scre...

Страница 25: ...nd 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 adjustme...

Страница 26: ...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 th...

Страница 27: ...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 2 NC NC NC 3 2 4 2 4 2 4 CR307 C 7 5 7 5 7 5 Reverse volt protection A 0 0 RX audio amp out CR4...

Страница 28: ...D 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 REF PIN TX RX SB DESCRIPTION IC308 1 2 4 2 4 Tone low pass filter 2 2 4 2 4 3 GND GND GND 4 5 0 5 0 5 2 4 2 4 6 2 4 2 4 7 5 0 5 0 8 3 2 3...

Страница 29: ...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 3 5 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 A...

Страница 30: ...HIP CAP 350 1364 0 Bottom C126 15119104 1uF X7R 0805 25V CERAMIC CHIP CAP 441 1542 0 Bottom C127 15119104 1uF X7R 0805 25V CERAMIC CHIP CAP 61 2203 0 Bottom C128 15119104 1uF X7R 0805 25V CERAMIC CHIP...

Страница 31: ...AMIC CHIP CAP 82 2765 180 Bottom C335 15180101 100pF CAPACITOR CHIP 0402 COG 5 366 2880 270 Bottom C336 15181332 0033uF CAPACITOR CHIP 0402 X7R 5 10 454 3156 90 Bottom C337 152B6106 10uF 10V 3 4 X 2 8...

Страница 32: ...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 T...

Страница 33: ...03 18414104 4 5T AIRCOIL 24AWG 0625 ID RHH SMT 1478 2880 180 Top L204 18433102 2T AIRCOIL SMT 5 0nH 120 X 145 1591 3250 90 Top L205 18110103 CHIP INDUCTOR 10uhy 1386 3262 90 Top L206 18414108 8 5T AIR...

Страница 34: ...39K OHM RESISTOR CHIP 0402 1 16W 5 117 1676 90 Top R118 47180103 10K OHM RESISTOR CHIP 0402 1 16W 5 49 1509 0 Bottom R119 47180102 1K OHM RESISTOR CHIP 0402 1 16W 5 49 1470 180 Bottom R120 47180681 6...

Страница 35: ...tom 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 R352 47100225 2 2M 0805 CHIP RESISTOR 44 2406 0 Top R353 47180103 10K...

Страница 36: ...6001029 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 ANTENNA AFS 450 ANTENN...

Страница 37: ...NG SST MINI 14500025 OWNER S MANUAL 14x 44x SERIES JMX SST 14540006 WARRANTY REGISTRATION CARD JMX 442 MODELS ONLY CASE LABELS 14220002 LABEL CONTROLS JMX 14222035 LABEL NAMEPLATE JMX 14290002 BLANK L...

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