Specifications

2. Preset R528 (HI PWR Set) and R526 (LO PWR
Set) on the Main PC board fully counter-clock-
wise.
VCO Tuning
3. Adjust C545 for a DC voltage of 2.45 ± 0.05 volts
at TP501. On base station units, check the mini-
mum and maximum transmitter frequencies to en-
sure that the DC voltage is between 1.0 and 4.0
volts.
4. With a frequency counter connected to the output
of TEST PROBE A (see Figure 6), hold TEST
PROBE A across R593 and adjust the trimmer ca-
pacitor inside Y501 for a frequency on the fre-
quency counter that is within ± 100 Hz of the
transmit frequency.
Exciter Tune-Up
5. On base units, set the unit to a channel which is
programmed for high power. On repeater units, in-
sure that the unit is programmed for high power.
6. Set R526 (LO PWR Set) at mid range and set
R528 (HI PWR Set) fully clockwise. Connect a
wattmeter and RF power attenuator/dummy load
(50 watt minimum rating and 30 dB minimum at-
tenuation) to the ANTENNA connector (TX AN-
TENNA connector on repeater units). Adjust
C566, C575, and C580 for maximum power out-
put. Repeat once. The output power should ex-
ceed 25 watts.
Transmitter Auto Power Leveling Adjustment
7. For repeater units, if the unit is to be programmed
for high power, adjust R528 (HI PWR Set) for the
desired output power. If the unit is to be pro-
grammed for low power, skip to the following step.
On base station units, change to a channel which is
programmed for high power and adjust R528 for
the desired output power.
8. For repeater units, if the unit is to be programmed
for low power, re-program the unit for low power
and adjust R526 (LOW PWR Set) for the desired
output power. On base station units, change to a
channel programmed for low power and adjust
R526 for the desired output power.
Deviation Adjustment
9. Preset R544 (MASTER DEVIATION) and R583
(BALANCE) to mid-range.
10. For base station units, set the unit to a non-
tone/data channel. For repeater units, insure that
the unit has not been programmed for tones. Con-
nect an FM demodulator through a power attenu-
ator or a directional coupler to the output of the
transmitter. The de-emphasis function should be
turned off and all low pass and high pass filters in
the demodulator removed except for a low pass fil-
ter with a cutoff frequency greater than 15 kHz.
Connect the output of the demodulator to an oscil-
loscope.
11. Plug a dummy microphone circuit (see Figure 5)
into modular microphone jack on the front panel.
Connect an audio generator to the dummy micro-
phone circuit and set the audio frequency to 1000
Hz . Adjust the output of the audio generator until
the sine wave on the oscilloscope just shows clip-
ping on the peaks. Increase the audio level by 20
dB (factor of 10 in voltage).
12. Adjust R544 (MASTER DEVIATION) trimmer
for ± 4.2 kHz deviation. Change the frequency of
the audio generator to 300 Hz and adjust R583
(BALANCE) for ±4.2 kHz deviation. Observe the
demodulated signal on the oscilloscope. The cor-
rect waveform is shown below:
a. Correct
b. Incorrect
c. Incorrect
AE/LZB 119 1882 R1B
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