Motorola Gm328 Gm338 Gm398 Detailed 6804112j18 E Manual

 GM328/GM338/GM398
Mobile Radios
VHF (136-174MHz)
Service Information
Issue: December, 2003 

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Table of Contents
Section 1 Model Chart and Technical Specifications
1.0 GM328/GM338/GM398 Model Chart ................................................................... 1-1
2.0 Technical Specifications ...................................................................................... 1-2
Section 2 Theory of Operation
1.0 Introduction .......................................................................................................... 2-1
2.0 VHF (136-174 MHz)...

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Section 4 VHF PCBs/Schematics/Parts Lists
1.0 Allocation of Schematics and Circuit Boards ....................................................... 4-1
1.1 Controller Circuits ........................................................................................... 4-1
2.0 VHF 1-25W PCBs / Schematics / Parts Lists ...................................................... 4-3
VHF (136-174 MHz) 1-25W 8486172B06  Top Side .............................................. 4-3
VHF (136-174 MHz) 1-25W 8486172B06...

1-1
Section 1
MODEL CHART AND TECHNICAL SPECIFICATIONS
1.0 GM328/GM338/GM398 Model Chart
GM Series, VHF 136-174 MHz
Model Description
AZM25KHC9AA1GM328 136-174 MHz 1-25W
AZM25KHF9AA5 GM338 136-174 MHz 1-25W
AZM25KHN9AA8GM398 136-174 MHz 1-25W
Item Description
X GCN6112_ GM328 Control Head Direct Mount
XGCN6114_GM338 Control Head Direct Mount
X GCN6115_ GM398 Control Head Direct Mount
XXIMUD6010_Tanapa WM 136-174 MHz 1-25W
X IMUD6023_ Tanapa WM 136-174 MHz 1-25W
XXXRAD4198_BNC 136-144 MHz, 1/4 Wave Roof...

1-2Technical Specifications
2.0 Technical Specifications
Data is specified for +25°C unless otherwise stated.
General Specifications
Channel Capacity
GM328
GM338
GM398
4
128
160
Power Supply 13.2Vdc (10.8 - 15.6Vdc)
Dimensions:  H x W x D (mm)  Depth excluding knobsGM328
56mm x 176mm x 177mm
(add 8mm for Volume Knob)
Dimensions:  H x W x D (mm)  Depth excluding knobsGM338
59mm x 179mm x 186mm (1 - 25W)
59mm x 179mm x 198mm (25 - 45W)
(add 9mm for Volume Knob)
Dimensions:  H x W x D (mm)  Depth excluding...

Technical Specifications1-3
*Availability subject to the laws and regulations of individual countries.Transmitter VHF
*Frequencies - Full BandsplitVHF 136-174 MHz
Channel Spacing12.5/20/25 kHz
Frequency Stability
(-30°C to +60°C, +25° Ref.)±2.5 ppm
Power 1-25W 
Modulation Limiting
±2.5 @ 12.5 kHz 
±4.0 @ 20 kHz
±5.0 @ 25 kHz
FM Hum & Noise-40 dB @ 12.5kHz
-45 dB @ 20/25kHz
Conducted/Radiated Emission (ETS)-36 dBm 1 GHz
Adjacent Channel Power-60 dB @ 12.5 kHz
-70 dB @ 25 kHz
Audio Response (300 -...

1-4Technical Specifications
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2-1
Section 2
THEORY OF OPERATION
1.0 Introduction
This Chapter provides a detailed theory of operation for the VHF circuits in the radio. For details of 
the theory of operation and troubleshooting for the the associated Controller circuits refer to the 
Controller Section of this manual.
2.0 VHF (136-174 MHz) Receiver
2.1 Receiver Front-End
The receiver is able to cover the VHF range from 136 to 174 MHz. It consists of four major blocks: 
front-end bandpass filters and pre-amplifier, first mixer,...

2-2VHF (136-174 MHz) Receiver
There are two 2-pole 44.85 MHz crystal filters in the high-IF section and 2 pairs of 455 kHz ceramic 
filters in the low-IF section to provide the required adjacent channel selectivity. The correct pair of 
ceramic filters for 12.5 or 25kHz channel spacing is selected via control line BWSELECT. The 
second IF at 455 kHz is mixed, amplified and demodulated in the IF IC. The processing of the 
demodulated audio signal is performed by an audio processing IC located in the...