5–5
Adjustments and Tests
5.3.4 FSK Balance Control
An FSK signal (used for automatic identification of FM repeaters) shifts the
frequencies of the 10.24–MHz crystal reference oscillator and the VCO.
Use an oscilloscope to observe the cathode end of D306. With no program, the
pulse will be less than 1 µsec wide. With an FSK input (a 20–Hz square wave at
the FSK input will work), set trim pot R345 for minimum pulse width.
The setting will vary slightly with operating frequency.
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) 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.
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.
To Next Page
Loading...
