Measurement Of Insertion Loss; Tuning The Amplifier - Mirage B-215-G User Manual

MIRAGE B-215-G
8. Upon application of power, the initial reading should be approximately .64 amps of current.
9. Locate the driver bias pot, R37, and raise the current 60 to 80 milliamps for a reading of
approximately .70 to .72 amps on the meter.
10. Locate and adjust the power amplifier bias pot, R42, to reflect an additional 20 milliamps on
the meter for a reading of approximately .90 to .92 amps.
11. Turn the unit OFF and remove the DC power.
12. Remove the shorted RCA plug from the RCA jack on the amplifier.
13. Disconnect the meter from the circuit and place the fuse back in the holder.

Measurement of Insertion Loss

1. Ensure that the power is in the OFF position on the front panel.
2. Set the frequency of the exciter radio to the center of the allocated band (In the case of the
Amateur band, 146.000 MHz).
3. Turn the exciter radio ON and adjust the output power to 1 watts FM or CW when keyed.
4. Verify that there is no reflected power.
5. Increase the power to 2 watts and measure the insertion loss through the relay contacts.
6. With 2 watts injected, the output watt meter should read 1.6 watts or more. The difference is
the insertion loss, which should be no more than .4 watts. The input reflected should read
less than 40 milliwatts.

Tuning the Amplifier

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NOTE: Key-up by applying RF during test only. While tuning & testing, always observe
current draw, spectrum analyzer and input VSWR.
1. Key the exciter radio and adjust the output power to 1 watt FM or CW.
2. Turn the DC power supply ON.
3. Place the front panel power switch in the ON position.
4. Quickly, and with minimum key up time, adjust the C65 trimmer capacitor on the output side
of the final power transistors for the maximum power output as shown on the output power
meter and minimum current draw.
5. Simultaneously observe the input reflected power meter and adjust C65 for the minimum
VSWR on the input while maintaining the maximum power that can be obtained on the output.
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