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

i8cvs domenico.i8cvs at tin.it
Sun Nov 30 02:34:50 PST 2008


----- Original Message -----
From: "Stan W1LE" <stanw1le at verizon.net>
To: <amsat-bb at amsat.org>
Sent: Saturday, November 29, 2008 3:33 PM
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)

Hi Stan, W1LE

Your message is very interesting and I found that the following pages
about the same matter are also very interesting

http://urgentcomm.com/mag/radio_versatile_sinad_meter/

http://www.repeater-builder.com/tech-info/receiversensitivity.html

I don't own a SINAD meter but only an Automatic Noise Figure Meter
that allow me to adjust a preamplifier or downconverter for the lovest
NF reading it in dB

Since you have both instruments I would love that you perform the
following measurement:

1) Get a low noise preamplifier and adjust it for the lovest NF using your
     HP-8970B and take note of it's value in dB

2) Put now the same preamplifier in front of a FM receiver and using
    your SINAD meter check if to get the maximum SINAD reading it is
    necessary or not to retune the preamplifier.

3) If retunig the preamplifier is necessary then reconnect the preamplifier
     to the HP-8970B and read the new value of NF

For the moment forget the problem to derive the value of the overall
NF of your receiving system from the SINAD measurement.

Tank you very much

73" de

i8CVS Domenico








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