RF Technology Eclipse Series Operation And Maintenance Manual page 35

6 FIELD ALIGNMENT PROCEDURE
detect. Thus the CPU knows (on power up) what frequencies are, or are not, possible to
be used with the PA.
The exciter does store some PA specific parameters, such as the Serial Number of the
PA, and also some offset values for the pre-amp drain current, and the output stage
drain current. These latter offsets improve the accuracy of the over current alarm
testing, (but are not strictly necessary). In order to set these parameters, it is advised
that this procedure be performed every time an exciter is used with a new External
Power Amplifier. Note that many of the stages can be skipped if they have been
performed before.
The program begins:
This procedure is used to calibrate an External Power Amplifier.
The existing PA's SERIAL NO is: 002356
Enter the new PA serial no:
Simply hit the Enter key here if the Serial Number is correct.
Take the lid off a PA, and set all three
bias Pots (R238,R239, and R240) fully clockwise.
Enter <RET> when done.
Now we will set the Bias currents in the PA.
Attach power to the PA.
Attach a calibrated millivoltmeter between TP100(+ve lead)
and TP101(-ve lead). Adjust R238 until the meter reads 50mV
Enter <RET> when done
Attach the calibrated millivoltmeter between TP102(+ve lead)
and TP103(-ve lead). Adjust R239 until the meter reads 10mV
Enter <RET> when done.
Adjust R240 until the meter reads 20mV
Enter <RET> when done.
Unless one of the RF power transistors has been replaced, the user should simply skip
these last four stages by hitting the Enter key four times.
Attach the Power Amplifier to the Exciter,
and ensure the PA is powered up.
Attach the PA output to a reflectometer, the reflectometer to a 50dB
(nominal) attenuator, and the attenuator to a calibrated power meter
Enter <RET> when this has been done");
Adjust C209 in the Power Amplifier
until there is a minimum in the dc voltage measured at TP204
Enter <RET> when done.
RF Technology T50 Page 35