Specifications

5–5
Adjustments and Tests
5.4 Metering Board Adjustments
5.4.1 Power Calibrate
While looking at RF Power on the digital panel meter, set the Power Calibrate trim
potentiometer to agree with an external RF power meter.
5.4.2 Power Set
With the front panel RF Output control fully clockwise, adjust the Power Set trim
pot to 10% more than the rated power (33 W for FM30, 110 W for FM100, 275 W
for FM250, 550 W for FM500) as indicated on an accurate external watt meter. If
the authorized power is less than the maximum watts, you may use the Power Set
to limit the range of the RF Output control. Operation below 100 watts is not
recommended as instability can occur which could damage the transmitter.
CAUTION
Possible equipment damage!
Operation below 100 watts can cause
oscillations and other problems that
could damage the transmitter.
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 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 R413 on the
Metering board. The current limit, in amperes, will be 0.35 amps higher than ten
times this voltage. Set the current limit for 16.5 amps or 1.615 volts at R413.