High-Power Adjustment; Reference Oscillator Adjustment; Deviation Adjustment - Motorola Spectra Service Manual

Connect the radio to the power meter and the
50-ohm load, and be sure the radio supply voltage is
13.6 Vdc ±0.2 V. Key the radio with the microphone
PTT button, and adjust by pressing VOL up or down
until the power meter indicates one-half the rated power
level. Then, dekey the radio. Press HOME to save the
new value and exit back to the "LO POWER" menu.
Press Mode to scroll through the three test mode
frequencies (LO 1 XXX, LO 2 XXX, and LO 3 XXX) and
check each as described above. Always recheck for
correct power level readings on all modes after power is
readjusted.
XIX. HIGH-POWER ADJUSTMENT
CAUTION
The radio transmit power is adjusted and tested
at the factory under tightly controlled conditions
with the most accurate test equipment available
and should rarely require field adjustment.
Each radio is set to the proper output level
while connected to an accurate 50-ohm load
impedance. Once the power level has been
set, the internal power control/protection circuit-
ry will reduce the power output whenever a load
impedance significantly different from 50 ohms
is sensed. If adjustment is required, be sure
the load impedance is as close as possible to
50 ohms to ensure proper radio operation.
Setting power to a level higher than that stated
in ALIGNMENT VIA IBM PERSONAL COM-
PUTER paragraph II. will reduce radio lifetime,
and adds no perceptible improvement in
system performance.
With "HI POWER" displayed, press HOME to enter
the adjustment mode.
"HI 1 XXX," where the "1" represents the applicable
alignment mode transmit frequency (see Table 9 ) to be
used, and "XXX" represents the high-level transmit
power output setting in radio memory. There is no direct
correlation between the value of "XXX" and the actual
power in watts; however, the power level increases
with the "XXX" value. Press Mode up to change to
"LO 3 XXX," which is the highest test frequency.
Connect the radio to the power meter and the
50-ohm load, and be sure the radio supply voltage is
13.6 Vdc ±0.2 V. Key the radio with the microphone
PTT button, and adjust by pressing VOL up or down
until the power meter indicates the rated power level,
then dekey the radio.
Press HOME to save the new value and exit back to
the "HI POWER" menu.
26
The display will show
Press Mode to scroll through the three test mode
frequencies (HI 1 XXX, HI 2 XXX, and HI 3 XXX) and
check each for power level of ±10% of initial power level
set. Always recheck for correct power level readings on
all modes after power is readjusted.
XX. REFERENCE OSCILLATOR ADJUSTMENT
The reference oscillator is preset at the factory under
tightly controlled conditions with the most accurate
test equipment available. Proper adjustment is critical
to system operation because of the narrow band-
width in the 900 MHz frequency band. If adjustment
is required, the radio's internal compartment must be
stabilized at room temperature (25 ±3°C; 77 ±5°F)
and a high-stability frequency counter (accuracy bet-
ter than 0.1 ppm, traceable to the national frequency
standard) must be used. Perform this adjustment as
soon as possible after turning on the radio.
With "REF OSC" displayed, press HOME to
enter the adjustment mode. The display will show
"REF1 XXX" where the "1" represents the applicable
alignment mode transmit frequency to be used (see
Table 9. Alignment Mode Frequencies), and XXX repre-
sents the current reference oscillator setting in radio
memory. There is no direct correlation between the
value of "XXX" and the actual frequency in MHz; how-
ever, the frequency increases with the "XXX" value.
Connect the frequency counter (refer to the NOTE
above) and a 50-ohm load to the antenna connector.
Press Mode to scroll to "REF3 XXX." Key the radio with
the microphone PTT and monitor the frequency counter
for a transmit frequency that is within ±230 Hz of the
transmit frequency for that test mode. If adjustment is
required, press VOL up or down until the correct fre-
quency reading is obtained on the counter. If you
cannot adjust the frequency within the prescribed range,
the radio requires further servicing.
When adjustment is complete, use HOME to save
the new value and return to the "REF OSC" display.
XXI. DEVIATION ADJUSTMENT
The transmit deviation is preset at the factory under
tightly controlled conditions with the most accurate
test equipment available. Correct deviation adjust-
ment is critical for operating in the narrow 900 MHz
frequency bandwidth and for remaining within FCC
specifications.
With "DEV" displayed, press HOME to enter
the adjustment mode.
"DEV1 XX," where the "1" represents the applicable test
NOTE
NOTE
The display will show