Motorola Gm328 Gm338 Gm398 Detailed 6804112j18 E Manual

 GM338
Mobile Radios
UHF1 40W Bipolar (403-470MHz)
Service Information
Issue: December, 2003 

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Table of Contents
Section 1 Model Chart and Technical Specifications
1.0 GM338 Model Chart............................................................................................. 1-1
2.0 Technical Specifications ...................................................................................... 1-1
Section 2 Theory of Operation
1.0 Introduction .......................................................................................................... 2-1
2.0 UHF (403-470 MHz) Receiver...

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Section 4 UHF PCB/Schematics/Parts Lists
1.0 Allocation of Schematics and Circuit Boards ....................................................... 4-1
1.1 Controller Circuits ........................................................................................... 4-1
2.0 UHF 25-40W PCB / Schematics / Parts List ........................................................ 4-3
UHF (403-470 MHz) 25-40W 8480643Z06 Top Side ............................................. 4-3
UHF (403-470 MHz) 25-40W 8480643Z06...

1-1
Section 1
MODEL CHART AND TECHNICAL SPECIFICATIONS
1.0 GM338 Model Chart
2.0 Technical Specifications
Data is specified for +25°C unless otherwise stated.
GM Series, UHF Band 1, 403-470 MHz
Model Description
AZM25RKF9AA5GM338 403-470 MHz 25-40W Conv Pref (Bipolar)
Item Description
XGCN6114_GM338 Control Head Direct Mount
X IMUE6012_ Tanapa WM 403-470 MHz 25-40W
XRAE4151_BNC 403-430 MHz, 1/4 Wave Roof Mount
X RAE4152_ BNC 450-470 MHz, 
1/4 Wave Roof Mount
XRAE4153_BNC 450-470 MHz, 3.5dB Gain Roof...

1-2Technical Specifications
*Availability subject to the laws and regulations of individual countries.Transmitter UHF
*Frequencies - Full BandsplitUHF 403-470 MHz
Channel Spacing12.5/20/25 kHz
Frequency Stability
(-30°C to +60°C, +25° Ref.)±2.0 ppm
Power 25-40W
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 - 3000...

2-1
Section 2
THEORY OF OPERATION
1.0 Introduction
This Chapter provides a detailed theory of operation for the UHF 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 UHF (403-470 MHz) Receiver
2.1 Receiver Front-End
The receiver is able to cover the UHF range from 403 to 470 MHz. It consists of four major blocks: 
front-end bandpass filters and pre-amplifier, first mixer, 1st...

2-2UHF (403-470 MHz) Receiver
The 2-pole 44.85 MHz crystal filters in the 1st IF section and two pairs of 455 kHz ceramic filters in 
the 2nd IF section provide the required adjacent channel selectivity. The correct pair of ceramic 
filters for 12.5 or 25 kHz channel spacing is selected via control line BWSELECT. The 2nd 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 controller...

Transmitter Power Amplifier (PA) 40 W2-3
2.4 2nd Intermediate Frequency (IF) and Receiver Back End
The 44.85 MHz 1st IF signal from the second IF amplifier feeds the IF IC (U3101) at pin1. Within the 
IF IC the 44.85 MHz high IF signal mixes with the 44.395 MHz second local oscillator (2nd LO) to 
produce the low IF signal at 455 kHz. The 2nd LO frequency is determined by crystal Y3101. The 
2nd IF signal is amplified and filtered by an external pair of 455 kHz ceramic filters (FL3112, FL3114) 
for 20/25...

2-4Transmitter Power Amplifier (PA) 40 W
3.1 Power Controlled Stage
The first stage (U4401) amplifies the RF signal from the VCO (TXINJ) and controls the output power 
of the PA. The output power of the transistor U4401 is controlled by a voltage control line feed from 
the PCIC pin4(U4501). The control voltage simultaneously varies the bias of two FET stages within 
U4401. This biasing point determines the overall gain of U4401 and therefore its output drive level to 
Q4421, which in turn controls the...