CATV Measurements
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2715 User Manual
measurements, divides the difference by two, and presents the quotient as the
measurement result.
The previous example used a Multiburst test signal. If the test signal is Line
Sweep, the procedure is the same, with the marker positioned on the highest
point in the detected sweep and then on the lowest point (or vice versa).
For this mode, the IN-CHANNEL RESPONSE is measured at two locations that
are chosen by placing a marker at the lowest point in the channel response and
taking a measurement, then moving the marker to the highest point in the
response and taking another measurement. The 2715 then divides the difference
between these measurements by two and presents the quotient as the measure-
ment result.
For this mode the IN-CHANNEL RESPONSE is usually measured at six
frequencies (which commonly correspond to burst frequencies of a test genera-
tor). The default test locations are –0.5 MHz, +0.5 MHz, +1 MHz, +2 MHz,
+3 MHz, and +3.75 MHz, all relative to the visual carrier.
NOTE
. Statutory proof-of-performance tests may require test frequencies other
than the default values.
Frequencies entered into the 2715’s IN-CHANNEL RESP SETUP menu (items 2
through 7) must match the frequencies actually produced by your test generator.
If a sweep generator is used, you may enter any frequency that is within the
generator’s range. However, do not enter frequencies that are closer than
500 kHz to the visual carrier.
When using a multiburst generator, you must enter the frequencies that it
actually produces. If you are not sure which frequencies your generator produces,
consult your generator manual, or use the 2715 to measure them. Do not use the
2715 count function to measure the multiburst frequencies. It may not produce
accurate results on burst and pulsed signals.
NOTE
. The “Out Of Range” message may appear after running an In-Channel
Response measurement. This message indicates one of these conditions.
H
IN-CHANNEL RESP SETUP menu test locations do not match generator
output
H
Flatness response of modulator or other cable TV system components is not
within
±
3.5 dB
Interactive Mode
Automatic Mode
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Страница 25: ...Getting Started ...
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