Theory of Operation:
Main Board
3-19
To select the 800 RX VCO, pin E5 (GPO1) must be at a high logic level and pin D5 (GPO2) and pin
D6 (GPO8) must be at a low logic level. The output of the 800 RX VCO is then split into two signals.
One to the Prescaler buffer input and the other to the prebuffer input. The output of the prebuffer is
then fed to pin 1 (RFC) of U738. The output of U738, pin 5 (RF2) then goes to the pi attenuator
(comprised of R703, R704 and R707) and then fed to the receiver section via the RX_LO
transmission line.
To select the 700 TX VCO, pin E5 (GPO1) must be at a high logic level and pin D5 (GPO2) and pin
D6 (GPO8) must be at a low logic level. The output of the 700 TX VCO is then split into two signals.
One to the Prescaler buffer input and the other to the prebuffer input. The output of the prebuffer is
then fed to pin 1 (RFC) of U738. The output of U738, pin 4 (RF1) then goes to the transmit injection
buffer (comprised of Q774 and surrounding circuitry). The output of the transmit buffer, then goes to
the transmit section via the TX_INJ transmission line.
To select the 700/800 MHz TX VCO, pin D5 (GPO2) must be at a high logic level and pin E5 (GPO1)
and pin D6 (GPO8) must be at a low logic level. The output of the 700/800 MHz TX VCO is then split
into two signals. One to the Prescaler buffer input and the other to the prebuffer input. The output of
the prebuffer is then fed to pin 1 (RFC) of U738. The output of U738, pin 4 (RF1) then goes to the
transmit injection buffer (comprised of Q774 and surrounding circuitry). The output of the transmit
buffer, then goes to the transmit section via the TX_INJ transmission line.
To select the 800 TX VCO, pin D6 (GPO8) must be at a high logic level and pin E5 (GPO1) and pin
D5 (GPO2) must be at a low logic level. The output of the 800 TX VCO is then split into two signals.
One to the Prescaler buffer input and the other to the prebuffer input. The output of the prebuffer is
then fed to pin 1 (RFC) of U738. The output of U738, pin 4 (RF1) then goes to the transmit injection
buffer (comprised of Q774 and surrounding circuitry). The output of the transmit buffer, then goes to
the transmit section via the TX_INJ transmission line.
Summary of Contents for Astro APX 3000
Page 1: ...APXTM TWO WAY RADIOS APX 3000 DETAILED SERVICE MANUAL ...
Page 2: ......
Page 4: ...Notes ...
Page 6: ...vi Document History Notes ...
Page 10: ...x Table of Contents Notes ...
Page 12: ...xii List of Tables Notes ...
Page 18: ...xviii List of Figures Notes ...
Page 22: ...xxii CommercialWarranty Notes ...
Page 46: ...3 20 Theory of Operation Main Board Notes ...
Page 84: ...3 58 Theory of Operation Bluetooth Notes ...
Page 208: ...6 64 Troubleshooting Waveforms LF CW on Spectrum Analyzer Notes ...
Page 222: ...7 14 Troubleshooting Tables List of Board and IC Signals Notes ...
Page 282: ...8 60 Schematics Boards Overlays and Parts Lists Main Board Block UHF1 84012513001_A Notes ...
Page 390: ...8 168 Schematics Boards Overlays and Parts Lists Main Board Block VHF 84012512001_A Notes ...
Page 456: ...9 8 Debugging Fixture Powering up Covert Board Notes ...
Page 468: ...Glossary 10 Glossary Notes ...
Page 472: ...Index 4 Index Notes ...
Page 473: ......