Hello The Net:
SINAD is nice because the complete path from RF thru IF thru audio demodulation can be tested. Also a cost effective approach, Last SINAD meter I got was about 100$. It is a HELPER Instruments,Inc. model SINADDER LINEAR 5 SINAD measurements require an external signal generator, and variable attenuator.
A noise figure meter can usually test the RF path or the RF thru IF path, but NOT to audio. For my HP-8970B, the IF would have to be more than 10 MHz, the low freq end of the machine. NF meters are about 10-20X $$$ the SINAD meter purchase.
I use my NF meter in a Y factor mode, which is essentially a signal to noise ratio. SINAD is also a Signal to Noise ratio, with Distortion taken into consideration. (S+N+D)/(N+D). When noise is very low, and distortion is also low, thus a S/N.
SINAD was used by Motorola and FM radio testing with a 1000Hz test modulation. Testing can also be used for testing SSB receivers, using a clean carrier with no modulation and tuning the RX for max signal, max S/N, max SINAD reading.
Both instruments have their utility.
Stan, W1LE Cape Cod, FN41sr
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