What is SINAD?
 

Is it only valid for AM and FM measurements?

I know its receiver sensitivity.

Is it Signal divided by Noise with distortion??

12 dB SINAD means what? The signal is 12 dB greater than noise and
distortion or
is it more complicated than that?

On Thu, 13 Oct 2005 17:27:14 -0700, crb wrote:

Is it only valid for AM and FM measurements?

I know its receiver sensitivity.

Is it Signal divided by Noise with distortion??

12 dB SINAD means what? The signal is 12 dB greater than noise and
distortion or
is it more complicated than that?

Thats about it.

It is the ratio of signal to noise and distortion, and it is measured
by setting up a test where the receiver produces output from a SSG
(typically for a 1KHz audio output) and notching out the 1KHz output
to measure the noise and distortion wrt the filtered 1KHz output.

I wrote a handy little calculator for converting rx senstivity
metrics, it is at http://www.vk1od.net/sc/RxSensitivityCalc.htm . The
conversions assume that the signal distortion component of the
Noise+Distortion is zero, in other words that the demodulation and
amplification process is linear.

SINAD is used widely to express the sensitivity of AM, FM and SSB
receivers. It is a much better method of measuring FM receivers than
the older "quieting" measurement.

Owen
--

Does anyone happen to know where there is a circuit diagram for a home
brew SINAD meter ?

Owen Duffy wrote:
On Thu, 13 Oct 2005 17:27:14 -0700, crb wrote:


Is it only valid for AM and FM measurements?

I know its receiver sensitivity.

Is it Signal divided by Noise with distortion??

12 dB SINAD means what? The signal is 12 dB greater than noise and
distortion or
is it more complicated than that?


Thats about it.

It is the ratio of signal to noise and distortion, and it is measured
by setting up a test where the receiver produces output from a SSG
(typically for a 1KHz audio output) and notching out the 1KHz output
to measure the noise and distortion wrt the filtered 1KHz output.

I wrote a handy little calculator for converting rx senstivity
metrics, it is at http://www.vk1od.net/sc/RxSensitivityCalc.htm . The
conversions assume that the signal distortion component of the
Noise+Distortion is zero, in other words that the demodulation and
amplification process is linear.

SINAD is used widely to express the sensitivity of AM, FM and SSB
receivers. It is a much better method of measuring FM receivers than
the older "quieting" measurement.

Owen
--

On Fri, 14 Oct 2005 01:03:00 GMT, David wrote:

Does anyone happen to know where there is a circuit diagram for a home
brew SINAD meter ?

You should also consider searching the net for software that will use
the PC sound card to make a SINAD measurement.

Owen
--

"David" wrote in message
...
Does anyone happen to know where there is a circuit diagram for a home
brew SINAD meter ?


While not homebrew , here is where you can find a manual and schematic for a
sinad meter.

http://www.repeater-builder.com/other-mfrs/sinadd.pdf

Thanks, that's what I was after.

Ralph Mowery wrote:
"David" wrote in message
...

Does anyone happen to know where there is a circuit diagram for a home
brew SINAD meter ?



While not homebrew , here is where you can find a manual and schematic for a
sinad meter.

http://www.repeater-builder.com/other-mfrs/sinadd.pdf

It is the ratio of (Signal + Noise+Distortion) to (Noise+Distortion) as
measured at the receiver audio output. It is measured using an RMS-reading
AC voltmeter , typically with a 1Khz modulation tone on the signal applied
to the receiver under test.

First you measure the audio signal out of the receiver using the AC RMS
meter. Then you apply a notch filter at the modulation frequency and measure
the residual noise+distortion, again using the RMS AC voltmeter. SINAD is
the ratio of the two measurements.

Joe
W3JDR



"crb" wrote in message ...
Is it only valid for AM and FM measurements?

I know its receiver sensitivity.

Is it Signal divided by Noise with distortion??

12 dB SINAD means what? The signal is 12 dB greater than noise and
distortion or
is it more complicated than that?

On Fri, 14 Oct 2005 00:58:35 GMT, Owen Duffy wrote:


It is the ratio of signal to noise and distortion, and it is measured
by setting up a test where the receiver produces output from a SSG
(typically for a 1KHz audio output) and notching out the 1KHz output
to measure the noise and distortion wrt the filtered 1KHz output.


That should be:
It is the ratio of signal and noise and distortion to noise and
distortion, and it is measured by setting up a test where the receiver
produces output from a SSG (typically for a 1KHz audio output) and
notching out the 1KHz output to measure the unfiltered output wrt the
noise and distortion.

I should also have mentioned the EIA test requires the receiver be set
to rated output with 1mV RF input at 60% of rated modulation, then the
RF output reduced to find the input level for 12dB SINAD.

You could measure it with soething like a HP334A Distortion Analyser,
but it is pretty tedious if you are trying to find the RF input for a
particular SINAD. Hence you see boxes that have an AGC controlled
amplifier deliving a constant voltage to the filter block. I have a
Motorola one (R1013A) that works ok, there were also Sinadders. Even
more convenient are the ones integrated into a communications monitor.
I don't believe these boxes do true RMS measurements.

An alternative if you have a standalone SSG and want to do SINAD
measurement is to use a PC sound card and software that does an FFT
and calculates the SINAD (using true RMS measurement). Spectrum Lab
does it, its free, but it is such a flexible / general tool, it may be
a bit daunting to get it working. The SpectrumLab menu "Quick Settings
/ Rx Equipment Tests / SINAD test" is a quick path to setup... but it
is still a quite complex package. A whole lot better than the style of
a HP334A though! SL is at http://www.qsl.net/dl4yhf/spectra1.html .

Owen
--

I use Baudline (http://www.baudline.com - Linux) for doing measurements
like that. Works well.

One should calibrate the soundcard first though.

There are a host of others..

Cheers Bob VK2YQA

Owen Duffy wrote:

On Fri, 14 Oct 2005 01:03:00 GMT, David wrote:


Does anyone happen to know where there is a circuit diagram for a home
brew SINAD meter ?


You should also consider searching the net for software that will use
the PC sound card to make a SINAD measurement.

Owen
--

Good info, Owen. I think the EIA test procedures really have FM or AM in
mind, rather than SSB or, what is exactly the same for SINAD purposes,
CW. The 60% figure just doesn't apply to SSB or CW. You would simply use
an unmodulated signal generator with the frequency offset to produce a 1
kHz tone in the receiver's audio output, preferrably centered in the
receiver's passband. Then a measure of rms af voltage at the receiver's
output with and without the 1 kHz filter would be made.

We don't hear much about SINAD testing procedures for SSB and CW. Even
the ARRL's test procedure manual glosses over the procedure for other
than FM.

Chuck
NT3G

Owen Duffy wrote:
On Fri, 14 Oct 2005 00:58:35 GMT, Owen Duffy wrote:



It is the ratio of signal to noise and distortion, and it is measured
by setting up a test where the receiver produces output from a SSG
(typically for a 1KHz audio output) and notching out the 1KHz output
to measure the noise and distortion wrt the filtered 1KHz output.



That should be:
It is the ratio of signal and noise and distortion to noise and
distortion, and it is measured by setting up a test where the receiver
produces output from a SSG (typically for a 1KHz audio output) and
notching out the 1KHz output to measure the unfiltered output wrt the
noise and distortion.

I should also have mentioned the EIA test requires the receiver be set
to rated output with 1mV RF input at 60% of rated modulation, then the
RF output reduced to find the input level for 12dB SINAD.

You could measure it with soething like a HP334A Distortion Analyser,
but it is pretty tedious if you are trying to find the RF input for a
particular SINAD. Hence you see boxes that have an AGC controlled
amplifier deliving a constant voltage to the filter block. I have a
Motorola one (R1013A) that works ok, there were also Sinadders. Even
more convenient are the ones integrated into a communications monitor.
I don't believe these boxes do true RMS measurements.

An alternative if you have a standalone SSG and want to do SINAD
measurement is to use a PC sound card and software that does an FFT
and calculates the SINAD (using true RMS measurement). Spectrum Lab
does it, its free, but it is such a flexible / general tool, it may be
a bit daunting to get it working. The SpectrumLab menu "Quick Settings
/ Rx Equipment Tests / SINAD test" is a quick path to setup... but it
is still a quite complex package. A whole lot better than the style of
a HP334A though! SL is at http://www.qsl.net/dl4yhf/spectra1.html .

Owen
--