[amsat-bb] Re: AMSAT-BB Digest, Vol 3, Issue 619 SINAD Testing

[Stan W1LE]

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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