Comment about Variations in the SNR Estimate
The user needs to be aware that the SNR estimate has an inherent statistical variation due to the effects
of random noise, especially when no emission is actually present. If a test is performed with the
instrument’s probe placed in a test cavity, it can be shown theoretically that the SNR will be greater
than 6 dB approximately 7 times out of 100. This is not a limitation of the instrument, but a
fundamental property of the method used to estimate the SNR in all emission testing. In order to reduce
the occurrence of this “false” emission, the instrument limits the minimum value of NF, which has the
effect of reducing the SNR for tests that have a low noise floor. As the noise level of the test increases,
the user will notice that more “false” emissions will appear, which is to be expected.
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