Motorola MC Micro Вирівнювання - Сторінка 4
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(7) Key the radio and observe tha waveform on an oscilloscope connected to demodulated output of
a test receiver. Test receiver should be non-deemphasized and there must be dc coupling between
the test receiver and the scope. (AC coupling is suitable if the corner frequency is 2 Hz or lower.)
Adjust R305 (REF MOD) for the flattest sguare-wave response with minimum tilt.
(8) Return the audio oscilator frequency to one kHz, 800 mV and repeat step 5.
1.5. TO ALIGN THE RECEIVER
Note
Adjust the transmiter VCO and reference oscilator before aligning the receiver
1.5.1 Receiver VCO
(1) Connect a high impendance (11 megaohms or greater) dc voltmeter from steering line test point
(SL) to ground.
(2) (Radios withmore then one receive frequency) Select the channel with highest receive freguency.
(3) Adjust the receiver VCO coil (L201) until the voltage meters reads 7.0 VDC.
(4) Select the channel with the lowest receive frequency and verify that test frequency is at least 2.5
VDC.
1.5.2. Receiver
(1) Find the tune-up frequency , f
(a) On single channel radios and multi chanel radios with a single receive frequency: f
(b) On multi chanel radios that have a receive bandwidth of two MHz or less: f
highest frequency channel
© On multi channel radios that have a receive bandwidth greater than two MHz but less than or
equal to four MHz find f
f
= (f
+ f
mid
highest
If one of the radio channels has a frequency within 500 kHz of f
channel. If not you must either get a tune-up PROM
programed to f
models contain a preprogramed tune-up channel, accessed by
temporarily shourting the TEST pins on the command board.
(2) Set the channel selector switch to the channel of the tune-up frequency as determined in step 1
above
(3) Connect a two ohm resistive load acros Pin 4 of J5 (hot lead) and Pin 5 of J5 (ground lead).
Monitor the audio output across this load resistor.
as follows:
tune
where:
mid
) : 2
lowest
or program the tune-up frequency f
mid
perform the tune-up on that
mid
into the radio (EZ models only). EV
mid
= f
tune
receive
= frequency of
tune