Swr Calibrate; Pa Current Limit; Display Modulation Calibration - Crown FM30 User Manual

5.4.3 SWR Calibrate

When the Carrier switch is off, or the RF power is less than about 5 watts, the SWR circuit
automatically switches to a calibrate-check mode. (See section 4.5 for more information.)
Set the digital panel meter to read SWR. With the Carrier switch off, set the SWR CAL trim
pot (R66) to read 1.03.

5.4.4 PA Current Limit

Since it may not be practical to increase the PA current to set the PA Current Limit control,
you may use this indirect method.
With the carrier turned off, look at the DC voltage at the right end of R186 in the Metering
circuit on the motherboard. The current limit, in amperes, will be 0.35 amps higher than ten
times this voltage. For example, for a current limit of 7.35 amps, adjust the PA Current Limit
control for 0.7 volts at R186 ; or 0.565 volts for 6.0 amps. Set the current limit for 4 amps
(FM50), 7 amps (FM150), or 9.5 amps (FM300).
5.5 Motherboard Configuration
See section 4.6.1 for motherboard jumper configuration.

5.6 Display Modulation Calibration

The Modulation Calibrate trim pot sets the sensitivity of the front panel Modulation bar graph
display.
This adjustment may be made only after the Output trim pot on the Audio Processor/Stereo
Generator board has been set. (See section 5.2.2.)
Set the Stereo-Mono switch to Mono.
Feed a sine wave source of about 2.5 kHz into the left channel at a level sufficient to put the
wideband gain-reduction indicator somewhere in the middle of its range.
Set the Modulation Calibrate trim pot so that the "90" light on the front panel Modulation dis-
play just begins to light.
Adjustments and Tests 5-5