HP 8591C User Manual page 91

Channel Measurements
Making Channel Measurements
Hum test
1. Select a channel or tune directly to the carrier to be measured. Make sure
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that the desired carrier is the highest on screen by adjusting the center
frequency and/or span as needed. Turn off modulation (optional), then
press Main 1 of 3 , HUM. See Figure 2-30.
Video Modulation Present
Note that after pressing
HUM,
present. If the video modulation is found to be on and the test result is greater than 3 percent, an
additional message appears advising the operator to re-test using a CW signal only
Pressing MORE INFO results in the analyzer performing a single sweep of
800 ms and performs a Fast Fourier Transform (FFT) on it to separate
power line related components. See Figure 2-31.
60 Hz, 120 Hz, 180 Hz, and 240 Hz are displayed. This is intended to
be used as a troubleshooting aid. A relatively high 60 Hz level implies
inadequate grounding or stray power utility neutral currents. A relatively
high 120 Hz level implies poor filtering of a full-wave rectifier in a power
card into the analyzer's card-insertion slot, press (SAVE_) display->card ,
then press (MODE) (ml to return to channel measurement mode. Refer
to Chapter 3 for the procedure on formatting a RAM card.
If you want to print the results, press (-1.
Press MAIN MENU to exit the test.
the first thing the analyzer does is determine if video modulation is