Instruction manual

Checks and Adjustments
5-12
1720/1721
g. Disconnect the Black Burst signal and the terminators from the
1720/1721.
11. Return Loss
Requirement -- Video Inputs: ≥40 dB to 6 MHz. Power on or off..
NOTE. Return Loss Check:
The Return Loss Check needs to be done only if repairs have been made on the
Input circuitry.
a. Connect a precision 50Ω cable from the spectrum analyzer RF Input to
the RF Output on the RF Bridge.
b. Connect a precision 50Ω cable from the spectrum analyzer TG Output to
the RF Input on the RF Bridge.
c. Select Demod/TG on the spectrum analyzer. Turn on the tracking
generator and set the tracking generator fixed level to 0.00 dBm.
d. Set the spectrum analyzer Span/Div to 1 MHz and the Resolution
Bandwidth to 30 kHz.
e. Set the spectrum analyzer Vertical Scale to 10 dB.
f. S et the spectrum analyzer Reference Level to the first major division
down from the top on the analyzer display.
g. Remove one of the cables from the R F Bridge.
h. Set the spectrum analyzer Frequency to 5 MHz and turn the Marker on.
SettheMarkerto6MHz.
i. Reconnect the cable to the RF Bridge.
j. Note -- the Reference Level Readout.
k. Adjust the spectrum analyzer External Attenuation Amplitude (on the
2712 Input menu) by the amount noted in part j. of this step. Note: The
Reference Level Readout should now be 0.00 dBm.
l. Connect the precision high-frequency terminator to the Device Under
Test connector on the RF Bridge.
m. Check -- that the frequency response from 0 MHz to 6 MHz is
≥40 dBm.
n. Return the spectrum analyzer frequency marker to 6 MHz if it was
moved.