Specifications

Setting and Using the Measurement Functions R&S FSH
1145.5973.12 4.52 E-10
Measuring the Carrier-to-Noise Ratio
(Available as of firmware version 8.0 or higher.)
The R&S FSH offers a carrier/noise measurement for measuring the ratio of carrier power to noise
power. The R&S FSH performs the measurement in two steps.
First, it measures the carrier power of a transmission channel, or you determine a reference power
which is then used for C/N calculation.
In the second step, the R&S FSH measures the noise power of an unoccupied transmission channel
and calculates the ratio of carrier power to noise power.
Determining the carrier power (reference power or reference level)
The R&S FSH offers the carrier power measurement for three different types of carrier signals.
• Digital Tx
In the Digital Tx operating mode, the channel power of a reference channel with a digitally
modulated signal is measured. This is common with digitally modulated carriers where power is
equally distributed across the channel, i.e. where the carrier power is independent of the modulation
signal.
• Analog TV
In the Analog TV operating mode, the peak power of the vision carrier is measured. This
measurement method is common with amplitude-modulated TV signals.
• CW Tx
In the CW Tx operating mode, the power of an unmodulated carrier is measured.
• Manual entry of a reference power or reference level
The R&S FSH also allows you to manually enter the reference power or the reference level which
will then be used for the carrier/noise calculation.
Noise power and carrier-to-noise power ratios C/N and C/N
0
For noise power measurements, the R&S FSH is set to an unoccupied transmission channel where it
measures the noise power in accordance with the selected noise channel bandwidth.
The R&S FSH defines the carrier-to-noise ratio by determining the ratio of the previously determined
reference to the measured noise power of the unoccupied transmission channel (C/N). The R&S FSH
displays the ratio logarithmically.
C/N = reference level – noise level in the channel
If required, the R&S FSH determines the ratio with reference to the noise power density of the
unoccupied transmission channel (C/N
0
).
C/N
0
= C/N + 10 lg (noise channel bandwidth/Hz)
Operating sequence:
¾ Press the MEAS key.
¾ Press the MEASURE softkey.
The menu for measurement functions opens.
¾ Using the cursor keys or the rotary knob, select
CARRIER / NOISE from the menu and confirm your
choice with the ENTER key or the MEASURE
softkey.
The R&S FSH activates the carrier/noise mode and
starts the reference measurement that was selected
last.