Ericsson LBI-38848D manual General Description, RF Board, Power Amplifier Board

LBI-38848D

	SPECIFICATIONS*
GENERAL
Regulatory Approval
FCC (United States)	AXATR-311-A2
DOC (Canada)	TR-311
Operating Voltage	13.8 Volts ±20%
Battery Drain
Receiver (13.8 Vdc)
Off	0.01 Amperes (maximum)
Squelched	0.75 Amperes (maximum)
Unsquelched	2.0 Amperes (maximum at 10 Watts audio,
	External Speaker)
Transmitter (13.8 Vdc)	11 Amperes (maximum at 25 Watts RF)
Channel Spacing	25 kHz (12.5 kHz NPSPAC)
Frequency Stability	±1.5 PPM (±0.00015%)
Temperature Range	-30C to +60C (-22F to +140F)
Dimensions (H x W x D)
(Less Accessories)
Height	5.3 cm (2.1 inches)
Width	18.2 cm (7.2 inches)
Depth	24.0 cm (9.5 inches)
Weight	3.0 kg (6.6 pounds)
Antenna Impedance	50 Ohms
TRANSMITTER
Frequency Range	806.0125-824.9875 MHz
Output Power	25 Watts (Intermittent duty cycle; EIA 20%)
Audio Sensitivity	125 mVrms (typical)
Spurious and Harmonics	<-16 dBm
Audio Distortion	5% maximum
Modulation Limiting	+5 kHz maximum (4 kHz max 821.000 - 824.9875 and
	866.000 - 869.9875 MHz)
FM Hum and Noise	-45 dB
Audio Frequency Response	Within +1, -3 dB of a 6 dB/octave pre-emphasis curve
Per EIA Standards	from 300-3000 Hz
RECEIVER
Frequency Range	851.0125-869.9875 MHz
Acceptable Frequency Displacement	±2.5 kHz minimum

GENERAL DESCRIPTION

The Dual Format MDX™ Mobile Radio is a synthesized, wideband radio that uses integrated circuits and microcom- puter technology to provide high performance trunked opera- tion. This radio operates in the Enhanced Digital Access Communications System (EDACS® ), GE-MARC trunking en- vironments and in conventional communications systems. The radio provides 25 Watts of RF power output in the 806.0125- 824.9875 MHz and 851.0125-869.9875 MHz bands. The re- ceiver operates in the 851.0125-869.9875 MHz band.

All radio functions are stored in a programmable Electri- cally Erasable PROM (EEPROM). The radio is field pro- grammable using an IBM compatible personal computer with the following equipment:

∙ Serial Programming Interface Module		TQ3370
∙	Programming Cable (19B801417P10)	TQ3372
∙	MDX Series Programming
	Software (EDACS)	TQ3373
∙	MDX Series Programming
	Software (GE-MARC only)	TQ3346

With the interface equipment and software, the computer can be used to program (or re-program) customer system frequencies, Channel Guard tones and options. Selection of options is done during radio initialization using the PC pro- grammer.

The Dual Format MDX™ Mobile Radio assembly con- tains the following circuit boards and assemblies:

∙	Power Amplifier Board	19C851822G1
∙	RF Board	19D902123G22
∙	System Board	19D901891G2
∙	Audio/Logic Board	19D903963G1
∙	Audio Amplifier Board	19D904025G2
∙	Front Cap Assembly	19D904151G1

The circuit boards are all mounted on a main casting to provide easy access for servicing. Interconnect 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.

Synthesizer

The synthesizer circuit generates all transmit and receive RF frequencies. The synthesizer frequency is controlled by the microprocessor located on the Audio/Logic Board. Frequency stability is maintained by a temperature compensated reference oscillator module. Transmit audio is processed on the Audio/Logic Board and applied to the synthesizer to modulate the VCO and TCXO. The buffered VCO output drives both the transmitter exciter and the receiver mixer.

Transmitter

The transmitter consists of a fixed-tuned exciter module, a PA module and a power control circuit. The PA module provides RF output to drive the antenna. The power control circuit controls the PA module to maintain a constant output power across the band. The RF output level is internally adjust- able for rated power. Thermistors in the control circuit protect the PA from overheating by reducing the power output level.

Receiver

The dual conversion receiver circuit consists of a front end section, 45.3 MHz first IF, a 455 kHz second IF, and FM detector. All audio processing and squelch functions are ac- complished on the Audio Board.

POWER AMPLIFIER BOARD

The PA board (19C851822G1) amplifies the RF board output then connects it back to the RF board where it is coupled through a PIN diode antenna switch, the low-pass filter and the directional coupler to provide 25 watts power output at the antenna connector.

Sensitivity (12 dB SINAD)	-113 dBm minimum
Spurious Response	70 dB minimum
Adjacent Channel Selectivity	68 dB minimum at ±25.0 kHz
Intermodulation Distortion	65 dB minimum
Audio Frequency Response	Within +2, -8dB of a 6 dB/octave de-emphasis curve
	from 300 -2700 Hz
Audio Output	10 Watts (External Speaker); 4 Watts (Internal Speaker)
Audio Distortion	5% maximum at 1 kHz

*These specifications are intended primarily for use by service personnel. Refer to the appropriate Specification Sheet for complete specifications.

Table 1 - Standard Tone Frequencies (Hz)

67.0	71.9	74.4	77.0	79.7	82.5	85.4	88.5	91.5	94.8	97.4
100.0	103.5	107.2	110.9	114.8	118.8	123.0	127.3	131.8	136.5	141.3
146.2	151.4	156.7	162.2	167.9	173.8	179.9	186.2	192.8	203.5	210.7

1.Do not use 179.9 Hz or 118.8 Hz in areas served by 60 Hz power distribution systems (or 100.0 Hz or 151.4 Hz in areas supplied with 50Hz power). Hum modulation of co-channel stations may "false" Channel Guard decoders.

2.Do not use adjacent Channel Guard tone frequencies in systems employing multiple Channel Guard tones. Avoid same-areas co-channel use of adjacent Channel Guard tones whenever possible. As stated in EIA Standard RS-220, there is a possibility of decoder falsing.

3.To minimize receiver turn-on time delay, especially in system using Channel Guard repeaters or receiver voting, choose the highest usable Channel Guard tone frequency. Do not use tones below 100 Hz when it is necessary to meet the receiver response time requirements of EIA Standard RS-220.

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