Operating instructions

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.

Each mV read across TP100(+ve lead), and TP101(-ve lead),

corresponds to 1mA of 1st stage Bias current.

For power control in the range 50 - 150W,

set the 1st stage bias to 35 - 40mA.

For power control in the range 20 - 60W, use a bias of 15 - 20mA.

Attach the millivoltmeter, and

adjust R238 for the bias required.

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.

Adjust the Forward Power Sense POT (R228) unti

tthe measured output power (adjusted for the attenuator and

reflectometer losses) is equal to the Preset Forward Power.

Enter <RET> when done.

Unless something has been modified in the power sense circuits, these last three stages

should be skipped by simply hitting the Enter key three times.

This next step allows the firmware to compute an offset in the output stage drain

current, so that the exciter’s ability to measure the output stage drain current is

significantly more accurate.

Measure the voltage across TP102(+ve lead)

and TP103(-ve lead), and enter the value measured

This next step allows the firmware to compute an offset in the pre-amp stage drain

current, so that the exciter’s ability to measure the pre-amp stage drain current is

significantly more accurate.

Measure the voltage across TP100(+ve lead)

and TP101(-ve lead), and enter the value measured

The next two stages can be skipped by simply hitting the Enter key twice.

Attach the reflectometer to an open circuit

Enter <RET> when this has been done

Adjust the Reverse Power Sense POT (R227) until