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

[Art McBride]

To All,
If you are using a LNA and you intend to perform a noise calculation,
knowing the noise figure of the LNA is important. 
LNA gain can shift the IF pass band in a receiver providing false indication
of noise contribution. In FM receivers it can shift the noise center of the
FM detector.
A noise figure measurement gives you the performance over the bandwidth of
the LNA not the bandwidth of the receiver. Noise tuning using the y factor
and a wide band receiver gives you the best performance of the LNA you have
as well as a means of comparing different LNAs independent of gain.

Art, KC6UQH 


-----Original Message-----
From: amsat-bb-bounces at amsat.org [mailto:amsat-bb-bounces at amsat.org] On
Behalf Of Stan W1LE
Sent: Saturday, November 29, 2008 6:34 AM
To: amsat-bb at amsat.org
Subject: [amsat-bb] Re: AMSAT-BB Digest, Vol 3, Issue 619 SINAD Testing

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
>    2.   Re: MMIC for LEO preamp? (RFI-EMI-GUY)
>
>   
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