446 Chapter9
IF Section
Log Amplifier (P/O A4 Assembly)
Total gain can be measured by injecting the specified power into A4J3
and measuring the total gain provided by A4U201C and A4U201E. The
following procedure provides a means of troubleshooting the linear
amplifiers:
1.On the 8564EC or 8565EC spectrum analyzer, press
PRESET,
SPAN, ZERO, SPAN, CAL, IF ADJ OFF, FREQUENCY, 1 GHz,
AMPLITUDE, −50 dBm, LINEAR, MORE, AMPTD UNITS, dBm, and
AMPLITUDE.
2. Disconnect W27 (coax 3) from A4J3 and connect the output of a
signal generator to A4J3.
3. Set the signal generator controls as follows:
Amplitude .................................................................. +6dBm
Frequency ............................................................... 10.7MHz
4.Simultaneouslydecreasethesignalgeneratoroutputand8564EC
or 8565EC spectrum analyzer REF LVL in 10 dB steps to
−90 dBm. At each step, the signal displayed on the spectrum
analyzer should be within one division of the previous position.
5. If a problem exists, isolate it by comparing the actual gain of
A4U201C and A4U201E with those listed in the above gain
guidelines.
6. Reconnect W27 (coax 3) to A4J3.
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