Chapter 5
Test and Measurement Functions
CX300 Meters
Rev. 001
CX300 ComXpert Operation Manual
22130634
5 - 40
February, 2022
5.6.9.3 Audio Signal to Noise Ratio Meter
Signal-to-Noise Ratio (SNR) is a measurement that compares the level of a desired signal
to the level of background noise. SNR is used to evaluate the receive performance of the
Unit Under Test (UUT) by identifying how well signal frequency components stand out from
noise interference in the signal.
supports limits which are described in
meter scales which are described in
. The SNR meter also
contains the following controls and settings:
Table 5-20 Demod SNR Meter Controls and Settings
Parameter
Description
Type
Selects the type of SNR measurement to be performed.
Hum & Noise
The Audio SNR Hum & Noise reading measures the
receiver of the radio under test. Audio SNR Hum & Noise is
a measurement of the level of the audio signal that is
demodulated by the radio when the test set sends a
modulated signal versus when the signal is not modulated.
Normal
When the Normal Audio SNR meter is selected the test set
transmits a user defined, modulated RF signal to a radio
under test. The test set transmits the signal, cycling the
modulation ON and OFF while the signal is being
transmitted. The radio under test demodulates the signal it
receives from the test set and sends an audio signal back to
the test set (via the Audio In connectors). The SNR reading
is the ratio of the level of the audio in the modulated signal
versus the level of audio in the demodulated signal.
Notch BW
This field sets the notch filter bandwidth used when performing
Hum & Noise SNR Measurements.
Notch Frequency
This field defines the frequency that is being measured when
performing noise measurements.
Notch Enable
Selects whether or not a notch filter is used for performing Hum
and Noise & SNR Measurements. When
Hum & Noise SNR
Notch Filter Mode
is enabled, the notch filter removes the sub
audible CTCSS or CDCSS tone.