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RF Technology PA220
2.6 RF Output Indicator
3 FIELD ALIGNMENT PROCEDURE
2.6 RF Output Indicator
The forward power voltage is compared with the pre-set dc reference voltage from RV2
by U1c. The output of U1c is used to turn on the RFO LED and provide an output
power logic signal to the test connector.
RV2 is normally set so that the RFO LED comes ON 1 - 3db below the nominal power
output level.
2.7 Over Temperature Protection
Thermistor RT1 is mounted to the case of output transistor Q1. If the transistor case
temperature rises above 90 Celcius the resistance of RT1 increases and Q5 is turned
ON.
This causes the TEMP LED to come on and also reduces the dc reference voltage to the
output power error amplifier U1d. The input power will then be reduced by the
transmitter ALC circuits and the output transistor is kept within safe operating limits.
3
Field Alignment Procedures
3.1 Output Power Level
1.
Set the unit up on a bench with the standard test equipment listed in table 2.
2.
Set RV1 and RV2 both fully counter-clockwise.
3.
Set the exciter to the desired operating frequency.
4.
Adjust RV1 to set the output power on the meter to the level at which you want the
RFO LED to illuminate.
5.
Adjust RV2 until the RFO LED just goes out.
6.
Adjust RV1 for the desired output power.
