Communication Concepts EB27A Construction Hints - Manual (Page 7)

This completes the assembly of the amplifier PC board. The unit may now be
tested.
TESTING
1. Connect a power supply of suitable current output to the amplifier. A regulated
power supply capable of delivering 28 volts DC at 25 amps is recommended for
this amplifier operation.
2. Connect the RF output of the amplifier through a power meter to a suitable 50
ohm dummy load of a rating capable of handling the power output (use a quality
50 ohm coax cable).
3. The potentiometer should be turned fully clockwise when the bias voltage was
set to minimum volts at the end of the bias voltage regulator test.
4. With a DC current meter connected in the power lead and without any RF applied
to the amplifier input, turn on the DC power supply and adjust the bias
potentiometer to the recommended idling current noted in the Application Note.
The minimum recommended collector idling current is 100mA per device or
200mA total.
5. Slowly bring up the input RF power until the RF output power equals the
maximum power recommended in the Application Note.
6. The output of the amplifier will contain harmonics of the input signal. Low pass
filters must be used on the output of the amplifier to reduce the harmonics to
meet FCC regulations for spectral purity. The filters shown in Figure 6 will
provide more than sufficient harmonic attenuation with less than 1 dB insertion
loss at the operating frequency.
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