Motorola Gm328 Gm338 Gm398 Detailed 6804112j18 E Manual

1-1
Section 1
MODEL CHART AND TECHNICAL SPECIFICATIONS
1.0 GM328/GM338/GM398 Model Chart
GM Series, UHF Band 1, 403-470 MHz
Model Description
AZM25RHC9AA1GM328 403-470 MHz 1-25W
AZM25RHF9AA5 GM338 403-470 MHz 1-25W
AZM25RHN9AA8GM398 403-470 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
XXIMUE6021_Tanapa WM 403-470 MHz 1-25W
X IMUE6039_ Tanapa WM 403-470 MHz 1-25W
XXXRAE4151_BNC 403-430 MHz, 1/4...

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
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 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 - 3000 Hz)+1 to -3 dB
Audio Distortion @1000Hz, 60%
Rated Maximum Deviation65 dB
Base...

1-4Technical Specifications
*Availability subject to the laws and regulations of individual countries.
Audio Response (300 - 3000Hz @ 20/25kHz)
(300 - 2550Hz @12.5kHz)+1 to -3 dB
Conducted Spurious Emission (ETS)-57 dBm 1 GHz
Receiver UHF 

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,...

2-2UHF (403-470 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...

UHF (403-470 MHz) Transmitter Power Amplifier (PA) 25 W 2-3
2.4 Low Intermediate Frequency (IF) and Receiver Back End
The 44.85 high 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 
low IF signal is amplified and filtered by an external pair of 455 kHz ceramic filters FL3112,...

2-4 UHF (403-470 MHz) Transmitter Power Amplifier (PA) 25 W
3.1 First Power Controlled Stage
The first stage (U4401) is a 20dB gain integrated circuit containing two LDMOS FET amplifier 
stages. It amplifies the RF signal from the VCO (TXINJ). The output power of stage U4401 is 
controlled by a DC voltage applied to pin 1 from the op-amp U4402-1, pin 1. The control voltage 
simultaneously varies the bias of two FET stages within U4401. This biasing point determines the 
overall gain of U4401 and...

UHF (403-470 MHz) Transmitter Power Amplifier (PA) 25 W 2-5
3.4 Directional Coupler
The directional coupler is a microstrip printed circuit, which couples a small amount of the forward 
power delivered by Q4441. The coupled signal is rectified by D4451. The DC voltage is proportional 
to the RF output power and feeds the RFIN port of the PCIC (U4501 pin 1). The PCIC controls the 
gain of stages U4401 and Q4421 as necessary to hold this voltage constant, thus ensuring the 
forward power out of the radio...

2-6UHF (403-470 MHz) Frequency Synthesis
U4502 is a temperature-sensing device, which monitors the circuit board temperature in the vicinity 
of the transmitter driver and final devices, and provides a DC voltage to the PCIC (TEMP, pin 30) 
proportional to temperature. If the DC voltage produced exceeds the set threshold in the PCIC, the 
transmitter output power will be reduced so as to reduce the transmitter temperature.
4.0 UHF (403-470 MHz) Frequency Synthesis
The synthesizer subsystem consists of...