----- Original Message ----- From: "Stan W1LE" [email protected] To: [email protected] 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
- 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
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