Motorola MC Micro Вирівнювання - Сторінка 5

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(4) Preset the slugs of L1 thru L7 for f

(5) Connect a dc voltmeter from the local oscilator test point (LO) to ground.

(6) Peak the injection filter coils L6, L5 and L7 in that order, for maximum dc voltage typiclly

between 2.1 and 3.5 VDC. Repeat until you cannot make the dc voltage increase any farther.

(7) Connect an RF signal generator to the anrenna connector and adjust it to generate an unmodulated

on channel signal strong enough to quiet receiver.

(8) Connect an ac voltmeter with bandwidth of at least 500 Hz (an HP331A distortion analyzer) from

the IF test point to ground. Increase the RF generator output until the ac voltmeter idicates

approximately 30 mV. Adjust the RF filter colils L1, L3, L4 and L5 until the voltmeter peaks.

Reduce the generator`s RF level as necessary to maintain approximately 30 mV RMS on the

meter during this process. Repeat the adjustmen until you can get no further increase in voltage.

(9) Set the RF level of the generator 1 mV. Modulate it with 1 kHz at 60% of full system deviation.

Full system deviation for channel spacing of 25 kHz is

~ 5 kHz; for 20 kHz ~ 4 kHz; for 12.5 kHz ~ 2.5 kHz. Adjust the volume control to get an audio

level of about one volt RMS acros the 2 ohm load. Slowly peak the quad coil, L54 for maximum

audio output.

(10) Adjust the squelch as follows:

(a) Preset the squelch control R59 CCW.

(b) Apply an on-channel RF signal at a level of one mV. Modulate with a one kHz tone at 60% of

full system deviation.

(d) Reduce the RF level untill the CCITT-weighted SINAD is 10 dB.

(e) Enable the carrier squelch mode with the front panel switch.

(f) Slowly turn the squelch control CW until the audio is squelched (muted) then very slowly turn

CCW until the radio just unsquelches (unmutes)

(g) Reduce the generator RF level to zero slowly increase the level until the radio just unsquelches and

verify that tha CCITT-weighted SINAD at this RF level

is between 8 and 12 dB SINAD. Readjust R59 slightly if necessary.

flush with the circuit board.

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