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 and UHF Range 2)—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
3 45
6 7 8
910 11
12 13
49
501
21
2 19
20 
						

							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
17
13
8
1110
319
18
1 2
31 32 
						

							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 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
3 45
6 7 8
910 11
12
13
49
501
21
2 19
20
MAEPF-27876-O 
						

							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 2
31 32 
						

							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 incoming unswitched battery voltage) enters the radio through the rear RF power 
amplifier connector (J0950) and is the main entry for DC power. The second path, through J2, pin 25, 
provides ignition sense to inhibit radio turn-on when the ignition switch is off.
When the control-head On/Off button is turned on, the three 9.3-V regulators power on the controller 
section, the RX/frequency generation unit (FGU) section, and the TX section. See Figure 3-11 for the 
UHF Range 1 and UHF Range 2 bands or Figure 3-12 on page 3-13 for the VHF and 700-800 MHz 
bands.
Figure 3-11.  DC Voltage Routing Block Diagram (UHF Range 1 and UHF Range 2)
VCC59.3V_FGU
9.3V_TX
GPIO KEYED_9.1_EN A+
SW_A+UWW_5VOn/Off
Controller Section RX / FGU Section Control Head
TX Section
J0401
A+19, 21
SWB+17
IGN20
1825 20, 22
24
SWB+ J0402
J2 J0950
9.3V
Regulator
U05009.33V
Regulator
U09509.3V
Regulator
U0951
Switch
3.0V
Regulator
U09622.85V
Regulator
U05011.85V
Regulator
U05071.55V
Regulator
U05023V
Regulator
U6002 3V
Regulator
U6750
FET
Q0503UNSW
5V Circuit
VR0500, R0507
SIOIC5V
Regulator
U05035V
Regulator
U0505
DRV_9.3V
9.3V
Regulator
U5570 
						

							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 of receiver front-end (RXFE). When reading the 
Theory of Operation, refer to your appropriate schematic and component location diagrams located 
in “Chapter 7. Schematics, Component Location Diagrams, and Parts Lists”. This detailed theory of 
operation will help isolate the problem to a particular component.
3.4.1 VHF (136–174 MHz) Band
The receiver circuits primary duties are to detect, filter, amplify, and demodulate RF signals in the 
presence of strong interfering noise and unintended signals. The receiver is broken down into the 
following blocks (Figure 3-13 on page 3-14):
• Front-end, which includes:
- 15 dB step attenuator
- PIN diode switches
- Three discrete filters
- Two low-noise amplifiers
-Mixer
• Back-end, which includes:
- Two crystal filters
VCC59.3V_FGU
9.3V_TX
GPIO KEYED_9.1_EN A+
SW_A+UWW_5VOn/Off
Controller SectionRX / FGU Section Control Head
TX Section
J0401
A+19, 21
SWB+17
IGN20
1825 20, 22
24
SWB+ J0402
J2 J0950
9.3V
Regulator
U05009.33V
Regulator
U09509.3V
Regulator
U0951
Switch
3.0V
Regulator
U09622.85V
Regulator
U05011.85V
Regulator
U05071.55V
Regulator
U05023V
Regulator
U6002 3V
Regulator
U6750
FET
Q0503UNSW
5V Circuit
VR0500, R0507
SIOIC5V
Regulator
U05035V
Regulator
U0505
MAEPF-27825-O 
						

							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 is 
improved by bypassing the first HPF and LNA. Preamp mode is characterized by higher sensitivity.
3.4.1.3  Preselector Filters
The front-end operates in the 136-174 MHz band. The front-end filters primary function is to provide 
protection against out-of-band spurious responses such as image, IF, half-IF, etc. while providing flat, 
low-loss response in the receive band. The front-end uses discrete LC filter technology. The first filter 
is a high-pass filter that protects the first LNA from strong out-of-band signals at frequencies which 
are below the receive band and is used in preamp mode only. The second and third filters are band-
pass filters that provide additional out-of-band spurious rejection.
3.4.1.4  Low-Noise Amplifiers (Q3255, Q3252)
The function of the Low-Noise Amplifiers (LNA) is to amplify the received signal with minimal noise 
contribution. The first LNA (Q3255) has 10 dB of gain and is activated in Preamp mode only. A 
clamping diode pair (D3256) located after the High Pass and before the first LNA protects the 
receiver from strong RF signals by limiting the signal amplitude going into the amplifier. The second 
LNA (Q3252) has 15 dB of gain. Both LNAs are biased with 9.3V.
Ant. SW.
Harm. FLT
RF Input
Att.
HPFLNA 1
LNALNA 2 Pre Mode
Std ModeBPF 1 BPF 2
Front-end
Back-end
Mixer
LO 2 Pole
Crystal
ABACUS
Back-end
IC2 Pole
Crystal