I
-
Test Descriptions
Composite Triple Beat
(CTB)
Test Description
1. The visual carrier peak level of the test channel (default is channel 4) is
measured.
2. Control line B of the analyzer auxiliary interface is set to a TTL-high level.
3. The center frequency of the analyzer is increased to the frequency
of the test channel plus the CTB offset of 6 MHz (default setting of
CTB
FREQ
OFFSET
).
4. The beat level is measured
5. The beat level is subtracted from the visual carrier peak level.
6. Control line B of the analyzer auxiliary interface is set to 0 volts dc.
The visual carrier peak To End the beat products, the analyzer center frequency is changed so that
level of the test channel any beat products in the gap between channels 4 and 5 can be measured. To
is measured
avoid measuring the skirts of the visual carrier, the resolution bandwidth
and frequency span of the analyzer are decreased. To optimize the distortion
measurement capability of the analyzers, the reference level is decreased to
bring the noise level within the Erst six divisions of the graticule, and input
attenuation is adjusted for the best dynamic range.
At this point in the CTB test, the control B line of the analyzer auxiliary
interface is set to a TTL high level. If you wish to momentarily turn off the
carrier, you may End it useful to use control line B (with additional circuitry)
to turn off the carrier.
8-19
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