Motorola GP340 Service Information

2-6 THEORY OF OPERATION
4.0 Frequency Generation Circuitry
(Refer to Figure 2-3 and the Frequency Synthesizer schematic diagram)
The Frequency Generation Circuitry is composed of two main ICs, the Fractional-N synthesizer
(U201), and the VCO/Buffer IC (U241). Designed in conjunction to maximize compatibility, the two
ICs provide many of the functions that normally would require additional circuitry. The synthesizer
block diagram illustrates the interconnect and support circuitry used in the region. Refer to the
relevant schematics for the reference designators.
The synthesizer is powered by regulated 5V and 3.3V which come from U247 and U248
respectively. The synthesizer in turn generates a superfiltered 4.5V which powers U241.
In addition to the VCO, the synthesizer must interface with the logic and ASFIC circuitry.
Programming for the synthesizer is accomplished through the data , clock and chip select lines from
the microprocessor. A 3.3V dc signal from synthesizer lock detect line indicates to the
microprocessor that the synthesizer is locked.
Transmit modulation from the ASFIC is supplied to pin10 of U201. Internally the audio is digitized by
the Fractional-N and applied to the loop divider to provide the low-port modulation. The audio runs
through an internal attenuator for modulation balancing purposes before going out to the VCO.
4.1 Synthesizer
(Refer to Figure 2-4 and the Synthesizer schematic diagram)
The Fractional-N Synthesizer uses a 16.8MHz crystal (FL201) to provide a reference for the
system. The LVFractN IC (U201) further divides this to 2.1MHz, 2.225MHz, and 2.4MHz as
reference frequencies. Together with C206, C207, C208, R204 and CR203 , they build up the
reference oscillator which is capable of 2.5ppm stability over temperatures of -30 to 85
°C. It also
provides 16.8MHz at pin 19 of U201 to be used by ASFIC and LVZIF.
The loop filter which consist of C231, C232, C233, R231, R232 and R233 provides the necessary
dc steering voltage for the VCO and determines the amount of noise and spur passing through.
Figure 2-3 Frequency Generation Unit Block Diagram
Voltage
Multiplier
Synthesizer
U201
Dual
Tran-
sistor
Loop
Filter
VCOBIC
U241
Low
Pass
Filter
Matching
Network
Attenuator
To
Mixer
To
PA D r ive r
VCP
Vmult1
Aux3
Aux4
MOD Out
Modulating
Signal
Vmult2
Rx VCO Circuit
Tx VCO Circuit
TRB
16.8 MHz
Ref. Osc.
Rx Out
Tx Out

Motorola GP340 Specifications

Power and Battery

power supply	Rechargeable Battery 7.5v
battery life with standard high capacity NiMH battery (low power)	11 hours
battery life with standard high capacity NiMH battery (high power)	8 hours
battery life with ultra high capacity NiMH battery (low power)	14 hours
battery life with ultra high capacity NiMH battery (high power)	11 hours
battery life with NiCD battery (low power)	12 hours
battery life with NiCD battery (high power)	9 hours
battery life with Li-lon battery (low power)	11 hours
battery life with Li-lon battery (high power)	8 hours

Operating Environment

operating temperature	-20°C to +55°C
sealing	Withstands rain testing per MIL STD 810 C/D/E and IP54
shock and vibration	Protection provided via impact resistant housing exceeding MIL STD 810-C/D/E and TIA/EIA 603
dust and humidity	Protection provided via environment resistant housing exceeding MIL STD 810 C/D/E and TIA/EIA 603

Transmitter Specifications

frequencies - full bandsplit	VHF: 136-174 MHz, LB1: 29.7-42 MHz, UHF: 300-350 MHz, LB2: 35-50 MHz, UHF1: 403-470 MHz
channel spacing	12.5/20/25 kHz
frequency stability	±2.5 ppm
power	136-174: 1-5W, 300-350: 1-4W, 403-470: 1-4W
modulation limiting	±2.5 @ 12.5 kHz, ±4.0 @ 20 kHz, ±5.0 @ 25 kHz
FM hum & noise	-40dB typical
conducted/radiated emission	-36 dBm <1 GHz, -30 dBm >1GHz
adjacent channel power	-60 dB @ 12.5 kHz, -70 dB @ 20/25 kHz
audio response (300-3000Hz)	+1 to -3 dB
audio distortion	3%

Receiver Specifications

frequencies - full bandsplit	VHF: 136-174 MHz, LB1: 29.7-42 MHz, UHF: 300-350 MHz, LB2: 35-50 MHz, UHF1: 403-470 MHz
channel spacing	12.5/20/25 kHz
sensitivity (12 dB SINAD) EIA	.25µV typical
sensitivity (20 dB SINAD) EN	.50µV typical
intermodulation EIA	70 dB
adjacent channel selectivity	60 dB @ 12.5 kHz, 70 dB @ 20/25 kHz
spurious rejection	70 dB
rated audio	0.5W
audio distortion @ rated audio	3% typical
hum & noise	-40 dB @ 12.5 kHz, -50 @ 20/25 kHz
audio response (300-3000 Hz)	+1 to -3 dB
conducted spurious emission	-57 dBm <1 GHz, -47 dBm <1 GHz

Weight and Dimensions

dimensions with standard high capacity NiMH battery	137 x 57.5 x 37.5 mm
dimensions with ultra high capacity NiMH battery	137 x 57.5 x 40.0 mm
dimensions with NiCD battery	137 x 57.5 x 40.0 mm
dimensions with Li-lon battery	137 x 57.5 x 33.0 mm
weight with standard high capacity NiMH battery	420 gm
weight with ultra high capacity NiMH battery	500 gm
weight with NiCD battery	450 gm
weight with Li-lon battery	350 gm