Motorola Astro Digital Mobile Radio Xtl5000 Detailled 6881096c74 B Manual

6881096C74-BMay 25, 2005
Theory of Operation: Main Board Major Sections 3-5
Figure 3-4.  XTL 5000 Main Board Sections (VHF High Power)—Side 2
Table 3-4.  XTL 5000 Main Board Sections (VHF High Power)—Side 2
3 RX Back-End 16 Antenna Switch
5 IF Filter 17 Rear Connector (J0402)
6 Controller Section 18 RX Front-End Biasing
12 TX PA 19 RX VCO Injection Stage
13 TX Power Control 20 TX VCO Injection Stage
14 Power Detector 21 FGU (Synthesizer)
15 Harmonic Filter
5
193
21
206
13
12
15 1416 18 

May 25, 20056881096C74-B
3-6Theory of Operation: Main Board Major Sections
3.2.2 UHF Range 1 (380-470 MHz) and UHF Range 2 (450-520 MHz) Band
The illustrations (Figure 3-5 on page 3-6 to Figure 3-8 on page 3-9) and their accompanying tables 
(Table 3-5 on page 3-6 and Table 3-8 on page 3-9) identify the location of the major sections of the 
main board.
Figure 3-5.  XTL 5000 Main Board Sections (UHF Range 1 Mid Power and UHF Range 2)—Side 1
Table 3-5.  XTL 5000 Main Board Sections (UHF Range 1 Mid Power...

6881096C74-BMay 25, 2005
Theory of Operation: Main Board Major Sections 3-7
Figure 3-6.  XTL 5000 Main Board Sections (UHF Range 1 Mid Power and UHF Range 2)—Side 2
Table 3-6.  XTL 5000 Main Board Sections (UHF Range 1 Mid Power and UHF Range 2)—Side 2
3 RX Back-End 13 TX Power Control
5 IF Filter 14 Power Detector
6 RX Front-End 15 Harmonic Filter
8 Controller Section 16 Antenna Switch
10 RX VCO 17 Rear Connector (J0402)
11 TX VCO 18 RX VCO Injection Stage
12 TX PA 19 FGU (Synthesizer)
5
6
1514
16
12...

May 25, 20056881096C74-B
3-8Theory of Operation: Main Board Major Sections
Figure 3-7.  XTL 5000 Main Board Sections (UHF Range 1 High Power)—Side 1
Table 3-7.  XTL 5000 Main Board Sections (UHF Range 1 High Power)—Side 1
1 Secure Connector (J0501) 8 Controller Section
2 Front Connector (J0401) 9 Audio Power Amplifier (PA)
3 RX Back-End (ABACUS III) 10 RX VCO
4 16.8 MHz Reference Oscillator 11 TX VCO
5 IF Filter 12 TX PA
6 RX Front-End 13 TX Power Control
7 Daughtercard
1 2
4
35
10
6
12 9
13 7 8
11 

6881096C74-BMay 25, 2005
Theory of Operation: Main Board Major Sections 3-9
Figure 3-8.  XTL 5000 Main Board Sections (UHF Range 1 High Power)—Side 2
Table 3-8.  XTL 5000 Main Board Sections (UHF Range 1 High Power)—Side 2
3 RX Back-End 13 TX Power Control
5 IF Filter 14 Power Detector
6 RX Front-End 15 Harmonic Filter
8 Controller Section 16 Antenna Switch
10 RX VCO 17 Rear Connector (J0402)
11 TX VCO 18 RX VCO Injection Stage
12 TX PA 19 FGU (Synthesizer)
5
3
21
6
20
13
12
16
15 14 

May 25, 20056881096C74-B
3-10Theory of Operation: Main Board Major Sections
3.2.3 700–800 MHz Band
The illustrations (Figure 3-9 and Figure 3-10 on page 3-11) and their accompanying tables (Table 3-9 
and Table 3-10 on page 3-11) identify the location of the major sections of the main board.
Figure 3-9.  XTL 5000 Main Board Sections (700–800 MHz)—Side 1
Table 3-9.  XTL 5000 Main Board Sections (700–800 MHz)—Side 1
1 Secure Connector (J0501) 8 Controller Section
2 Front Connector (J0401) 9 Audio Power...

6881096C74-BMay 25, 2005
Theory of Operation: Main Board Major Sections 3-11
Figure 3-10.  XTL 5000 Main Board Sections (700–800 MHz)—Side 2
Table 3-10.  XTL 5000 Main Board Sections (700–800 MHz)—Side 2
3 RX Back-End 16 Antenna Switch
5 IF Filter 17 Rear Connector (J0402)
6 Controller Section 18 RX Front-End Biasing
12 TX PA 19 RX VCO Injection Stage
13 TX Power Control 20 TX VCO Injection Stage
14 Power Detector 21 FGU (Synthesizer)
15 Harmonic Filter
MAEPF-27877-O
5
18
1514
16
12
17
13
6
20
321
19
1...

May 25, 20056881096C74-B
3-12Theory of Operation: Radio Power Distribution
3.3 Radio Power Distribution
This section provides information on DC power distribution in XTL 5000 radios. In the XTL 5000 
radio, power is distributed to three boards: the main board, control head, and secure interface board.
Power for the radio is supplied by the vehicle’s 12-V battery. When using a desktop adapter unit, an 
external DC power supply can be connected to replace the vehicle’s battery source.
A+ (referred to as...

6881096C74-BMay 25, 2005
Theory of Operation: Receiver Front-End3-13
Figure 3-12.  DC Voltage Routing Block Diagram (VHF and 700–800 MHz)
The 9.3 V and the A+ voltage are the main DC power for the RF section. The 9.1 V (referred to as 
“keyed 9.1 V”) is controlled by the VOCON board through P501, pin 45. This DC voltage enables the 
transmitter’s RF power amplifier when the VOCON board senses a lock detect from the synthesizer.
3.4 Receiver Front-End
This section provides a detailed circuit description...

May 25, 20056881096C74-B
3-14Theory of Operation: Receiver Front-End
- Low-noise IF amplifier
- ABACUS III digital back-end IC
Figure 3-13.  Receiver Block Diagram (VHF)
3.4.1.1  15 dB Step Attenuator (U3250)
The 15 dB step attenuator provides protection from strong on-channel signals and interferences.
3.4.1.2  PIN Diode Switches
The VHF front end operates in two modes: Standard mode and Preamp mode. The PIN diode 
switches select between the two modes. In standard mode the intermodulation performance...