R&S FSH
Measuring the Carrier-to-Noise Ratio
1145.5973.12 4.57
E-11
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The span is coupled to the channel bandwidth. When changes are made, the R&S FSH
automatically sets the appropriate span.
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The resolution bandwidth is coupled to the channel bandwidth. If it is set manually, it should be
between 1% and 4% of the channel bandwidth. This ensures that the R&S FSH measures the
channel power with good selectivity with respect to adjacent channels.
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The video bandwidth is coupled to the resolution bandwidth. If the RMS detector is used, the video
bandwidth must be at least three times the resolution bandwidth. Thus, the video filter does not
impair the power measurement by compressing signal peaks.
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The RMS detector is recommended. It ensures that the R&S FSH always measures the power
correctly, irrespective of the measurement signal characteristics.
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Set the sweep time in such a way that the result is stable. If the sweep time is extended, the
R&S FSH also increases the integration time for the RMS detector, thus yielding measured values
that are more stable.
Press the NOISE MEASURE softkey to start the measurement. For calculation purposes, the R&S FSH
uses the reference value that was last measured or manually set. During the noise channel
measurement, it outputs the reference value at the top left edge of the display.
Setting the noise channel
The noise channel is set by entering the channel number in accordance with the selected
channel/frequency table, or by entering the channel center frequency, the vision carrier frequency or the
8VSB/ATSC pilot frequency.
Press the NOISE MEASURE softkey.
The R&S FSH starts the noise channel measurement
in the noise channel last set and opens the NOISE
MEASURE menu for setting a new channel.
Using the rotary knob or the cursor keys, select the
desired noise channel entry and confirm your choice
with the ENTER key or the NOISE MEASURE
softkey.
The appropriate entry field opens.
Using the numeric keys, enter the channel or the
frequency of the desired transmission channel and
terminate your entry with the appropriate unit key or
the ENTER key.
The R&S FSH displays the frequency spectrum of the
noise channel as symmetrical to the channel center.
You can alternatively enter the channel center frequency using the FREQ key.
