Understanding SINAD

[@3sierra15]

This was the clearest explanation I have yet to find anywhere. Thank you.

[@egbertgroot2737]

Absolute excellent explanation!

[@W1RMD]

Thank you! I've always wondered what this was.

[@g0fvt]

Thank you for the upload!

[@zynthos9]

The harmonics and noise are generated by the receiver in this case?

[@pauldenisowski]

Good question. Since we're using SINAD to measure receiver sensitivity, we're measuring distortion created within the receiver. So it's really important that our test signal be as spectrally pure as possible with a good SNR.

[@adrian_sp6def]

question to calculation of D part (distortion). Should I sum all SNR-s for harmonics? for example D = SNR(h_1) + SNR(h_2) + ... ?

[@acestudioscouk-Ace-G0ACE]

Very clearly an well explained, thak-you.

[@pauldenisowski]

Thanks for the feedback!

[@howardhiggins9641]

Clear explanation but how sharp does the notch filter have to be to make a good SINAD meter, or equivalently a good SINAD measurement ?

[@g0fvt]

I am not an authority on this but there is an ETSI definition. It defines a notch filter (ETR 027). With the standard tone frequency of 1 kHz, it states that a filter used for SINAD measurements shall be such that the output the 1000 Hz tone shall be attenuated by at least 40 dB and at 2000 Hz the attenuation shall not exceed 0.6 dB. The filter characteristic shall be flat within 0.6 dB over the ranges 20 Hz to 500 Hz and 2000 Hz to 4000 Hz. In the absence of modulation the filter shall not cause more than 1 dB attenuation of the total noise power of the audio frequency output of the receiver under test.

[@themouas]

After watching to this video I guess there is no standard way of measuring sinad, the way we measure sinad is we should get 12dB Sinad at .2uV not .3uV.

[@pauldenisowski]

Most manufacturers specify SINAD at 12 dB, so this is a the de facto "standard" used. But generally speaking, there's no "passing" or "failing" value for SINAD -- lower voltage values simply mean "better" sensitivity. In my experience, SINAD is most useful as a comparative measurement: a receiver with a lower 12 dB voltage value is more "sensitive" than one with a higher value. Hope that helps!