Figure 3-4. Receiver Block Diagram - Motorola ASTRO XTS 5000 Detailed Service Manual

Theory of Operation: Transceiver Board
3.1.1.3 Antenna Port J2
Antenna port J2 is a surface-mount, miniature coaxial connector for the antenna cable.
3.1.1.4 Serial EEPROM
The serial, electrostatically erasable, programmable, read-only memory (EEPROM), U907 in VHF
and 700–800 MHz or U4 in UHF Range 1, holds all of the transceiver tuning data. This allows
transceivers to be tuned in the factory and installed in the field without retuning.
3.1.1.5 Power Conditioning Components
DC power-conditioning components include zener diodes, capacitors, ferrite beads, a power
inductor, and the fuse. Diodes VR1 and VR2 provide over-voltage protection. Ferrite beads
(designated E1, etc.) and capacitors suppress electromagnetic interference from the transceiver.
The power-line filter consisting of L1, C13, and C14 for VHF radios or L1, C10, and C11 for UHF
Range 1 and 700–800 MHz radios, suppresses digital noise from the VOCON board switching
power supplies that could degrade the transmitter spectral purity.
Pass transistor Q1 switches the battery voltage to the transceiver when control signal SWB+ or SB+
from the VOCON board is asserted high. This increases the transceiver's immunity to conducted
interference that might be present on SWB+ or SB+, such as from switching voltage regulators on
the VOCON board.
Ground clips G1 through G12 make contact between the transceiver board ground and the radio
chassis. The chassis connection is a necessary electrical reference point to complete the antenna
circuit path. Shields SH101 through SH700 and the tool hole appear on the schematic to show their
connection to ground.
3.1.2 Receiver
The XTS 5000 transceiver has a dual-conversion superheterodyne receiver.
the major receiver components:
• Receiver Front End
• Receiver Back End
RF Input
Harmonic
Filter
XTAL
Filter
6881094C31-D
RX Front End
Tuneable
Preselector
Antenna
Filter
LNA
Switch
ABACUS III - RX Back End
CKO
LO

Figure 3-4. Receiver Block Diagram

Tuneable
1st LO
Preselector
Filter
1st
Mixer
3
RX_SSI_ DATA
ADC
to VOCON Board
MAEPF-27278-A
3-5
Figure 3-4 illustrates
July 21, 2004