SMX920 Base Station & Repeater
Technical Manual
RELM/
BK RADIO
24
♦
With PTT ON measure the PA bias current at the Gates of the FET’s. The Bias
current is band dependent. This is done by monitoring the current drain of the
whole PA with CN1 disconnected. Link the gate of TR2 to GND. Measure
current consumption (VHF High Band 200mA ,UHF 400mA.) This can be adjust
by RV2. Measure gate volts
≈
3.4V
Remove link from TR2. Measure current consumption, adjust RV1 so that
current is 2Amp total (VHF & UHF). Measure gate volts
≈
3.9V
♦
Connect the RF output Connector CN3 with a coax lead to a power meter. Turn
ON the supply voltage and the signal generator RF output, PTT the PA and
increase the generator output (
Don’t 24 dBm
) whilst measuring the
output power output (
≥
50watts@ +25dBM ).
♦
If output power is low then turn the supply voltage OFF and lift one side of the
capacitors connecting to the directional coupler and solder a flying lead to the
lifted side. Connect the earth of the flying lead to the earth of the PA..
♦
Turn ON the supply voltage and the signal generator RF output, PTT the PA and
increase the generator output (
Don’t 24 dBm
) whilst measuring the
output power output (
≥
55watts@ +25dBM ).
♦
If all the above tests didn’t pass then the TR1 or TR2 may be faulty. Return to
your nearest Customer Service Centre
