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LBI-38960
SPECIFICATIONS*
GENERAL
Operating Voltage
Battery Drain
Receiver (13.8 Vdc)
Off
Squelched
Unsquelched
Transmitter (13.8 Vdc)
Channel Spacing
Frequency Stability
Temperature Range
Dimensions (H x W x D)
(Less Accessories)
Height
Width
Depth
Weight
Antenna Impedance
TRANSMITTER
Frequency Range
Output Power
Audio Sensitivity
Spurious and Harmonics
Audio Distortion
Modulation Limiting
FM Hum and Noise
Audio Frequency Response
RECEIVER
Frequency Range
Acceptable Frequency Displacement
Sensitivity (12 dB SINAD)
Spurious Response
Adjacent Channel Selectivity
Intermodulation Distortion
Audio Frequency Response
Audio Output
Audio Distortion
* These specifications are intended primarily for use by service personnel. Refer to the appropriate Specification Sheet for
complete specifications.
2
13.8 Volts ±20%
0.01 Amperes (maximum)
0.8 Amperes (maximum)
3.5 Amperes (maximum at 10 Watts audio, External Speaker)
10.5 Amperes (maximum at 25 Watts RF)
25 kHz
±1.5 PPM (±0.00015%)
-30°C to +60°C (-22°F to +140°F)
5.3 cm (2.1 inches)
18.2 cm (7.2 inches)
24.0 cm (9.5 inches)
3.0 kg (6.6 pounds)
50 Ohms
806.0125 - 820.9875 MHz and 851.0125 - 865.9875 MHz
25 Watts (Intermittent duty cycle; EIA 20%)
75-105 mVrms
less than -16dBm
5% Maximum
+5 kHz maximum (4 kHz max 806.000 - 820.9875
and 851.000 - 865.9875 MHz)
-45 dB
EIA/TIA RS-603
851.0125 - 865.9875 MHz
±2.5 kHz
-113 dBm minimum
70 dB minimum
68 dB minimum at ±25.0 kHz
65 dB minimum
EIA/TIA RS-603
10 Watts (External Speaker); 4 Watts (Internal Speaker)
7.5 Watts (External Speaker) with Remote Mount Kit
5% maximum at 1 kHz
GENERAL DESCRIPTION
The Ericsson/GE MDX™ GE-MARC mobile radio is a
synthesized wideband radio that uses integrated circuits and
microcomputer technology to provide high performance
trunked operation. The radio provides 25 watts of RF power
output in the 806 to 821 MHz and 851 to 866 MHz trunking
bands without retuning. The receiver operates in the 851 to
866 MHz band without retuning.
All radio functions are stored in a programmable electri-
cally erasable PROM (EEPROM). The radio is field program-
mable using an IBM compatible personal computer with the
following equipment:
• Serial Programming Interface Module TQ-3310,
• GE Programming Cable TQ-3372, and
• TMX-8825/MDX GE-MARC Programming Software
TQ-3344 or TQ-4344.
With the interface equipment and software, the computer
can be used to program (or reprogram) customer system fre-
quencies, Channel Guard tones and options. Programming is
done through the radio.
The MDX GE-MARC radio assembly consists of the fol-
lowing circuit boards and assemblies:
• RF Board (19D902123)
• PA Board (19C851822)
• Audio Board (19D902188)
• Logic Board (19D902172)
• System Board (19D901891)
• Audio Amplifier Board (19D904025)
• Front Cap Assembly (19D904151)
The circuit boards are all mounted in a main casting pro-
viding easy access for servicing. Interconnecting cables and
plugs are used to connect the boards to eliminate pinched wires
and other wiring problems.
RF BOARD
The RF board includes the programmable frequency syn-
thesizer, transmitter exciter, receiver front end and IF circuitry,
and PIN diode Tx-Rx switch.
LBI-38960
Synthesizer Circuit
The synthesizer generates all transmit and receive RF fre-
quencies. The synthesizer frequency is controlled by the mi-
croprocessor located on the Logic Board. Frequency stability
is maintained by a temperature compensated reference oscilla-
tor module. Transmit audio is processed on the Audio and
Logic Boards, and applied to the synthesizer to modulate the
VCO. The buffered VCO output drives both the transmitter
exciter and the receiver mixer.
Transmitter Circuit
The transmitter circuit consists of a fixed-tuned exciter
module, a PA module, a power control circuit, a PIN diode an-
tenna switch, and a low pass filter.
The PA module provides RF output to drive the PA Board.
The power control circuit controls the PA module by sampling
the PA board output to maintain constant output power across
the band. The RF output level is internally adjustable for rated
power. A thermistor in the control circuit protects the PA from
overheating.
Receiver Circuit
The dual conversion receiver circuit consists of a front end
section, 45.3 MHz first IF, a 455 kHz second IF, and FM detec-
tor. All audio processing and squelch functions are accom-
plished on the Audio Board.
PA BOARD
The PA Board amplifies the RF Board PA module output to
the rated output of 25 Watts. The 25 Watt output is fed back to
the RF Board where the power control circuit, the antenna
switch, and the low pass filter are located.
AUDIO BOARD
The Audio Board provides analog to digital and digital to
analog conversion of the receive and transmit audio for digital
processing by the Logic Board. The board also contains audio
filtering, conventional analog tone processing, and the receiver
squelch.
LOGIC BOARD
The Logic Board controls the main operation of the radio
and digitally processes the receive and transmit audio. The
board contains a microprocessor and associated memory cir-
cuits including an EPROM for controlling the processor and a
programmable "personality" electrically erasable PROM
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