HP 8530A, Руководство по эксплуатации и программированию, Страница: 328 / 439

Service Functions
Figure 17-13. Gain Stages in the IF section
Y ou will notice that, in Figure 17-12, the 100 kHz mixers are shown as having only a single
output each. This is not really true . Figure 17-13 shows a closer representation of the
actual circuitry . The dierent signals (a1, a2, b1, and b2) are split o and routed to input
selectors. When you select a specic parameter , a ratio such a b1/a1 is selected. The receiver
automatically selects the correct positions on the input selector to send the b1 signal to the test
channel, and a1 to the reference channel.
The signals then go to a series of 12 dB ampliers . In automatic IF gain mode , the receiver
controls these ampliers . These ampliers can also be controlled manually with the softkeys in
the IF Gain Select Menu.
How to Use Manual IF Gain Controls Properly
Y ou can solve the IF O VERLO AD problem by using manual IF gain, and setting it as necessary
for the higher power level.
Press 4
SYSTEM
5
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SERVICE FUNCTIONS
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IF GAIN . Then select gain control for either the
test or reference path with
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TEST AMP. GAIN or
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REFERENCE AMP. GAIN . The manual gain
control softkeys are now displayed:
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GAIN: (MIN) 0
Turns all four ampliers OFF for that test or reference path (0 dB gain).
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GAIN: 1
Turns one amplier ON for that test or reference path (12 dB gain).
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GAIN: 2
Turns two ampliers ON for that test or reference path (24 dB gain).
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GAIN: 3
Turns three ampliers ON for that test or reference path (36 dB gain).
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GAIN: (MAX) 4
Turns all four ampliers ON for that test or reference path (48 dB
gain).
No matter which gain setting you choose , the receiver adjusts displayed power levels
automatically .
Using System Functions 17-21