"chuck" wrote in message
ink.net...
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.

The old Canadian Department of Communications Document RSS 125 Issue 1,
Released August 1st, 1976, precisely describes the method of SINAD
measurements for SSB equipment. In the past 25 years or so, HP's distortion
analyzers (such as the HP8903B) were used for this measurement. In the late
60s and early 70s I have seen Heathkit distortion analyzers used for SINAD
measurements. The latest versions of RSS125 seem to be more in line with
FCC standards, where receiver specifications are not required for
certification purposes (See
http://www.agiletestgroup.com/ICCertifications.html).

73,

Frank

Thanks for the info, Frank.

Actually, the RSS125 on the site doesn't contain the procedure, but
RSS181, also available at that site, does.

FWIW, the procedure is basically what has been discussed, except that
the signal generator output to be recorded as the receiver's sensitivity
is that level which produces a 12 dB SINAD at 50% of rated audio output!
Probably a more realistic test than allowing the AF stage to operate at
a low-distortion level of something like 1% of rated output.

73,

Chuck
NT3G


Frank wrote:


The old Canadian Department of Communications Document RSS 125 Issue 1,
Released August 1st, 1976, precisely describes the method of SINAD
measurements for SSB equipment. In the past 25 years or so, HP's distortion
analyzers (such as the HP8903B) were used for this measurement. In the late
60s and early 70s I have seen Heathkit distortion analyzers used for SINAD
measurements. The latest versions of RSS125 seem to be more in line with
FCC standards, where receiver specifications are not required for
certification purposes (See
http://www.agiletestgroup.com/ICCertifications.html).

73,

Frank

"chuck" wrote in message
link.net...
Thanks for the info, Frank.

Actually, the RSS125 on the site doesn't contain the procedure, but
RSS181, also available at that site, does.

FWIW, the procedure is basically what has been discussed, except that
the signal generator output to be recorded as the receiver's sensitivity
is that level which produces a 12 dB SINAD at 50% of rated audio output!
Probably a more realistic test than allowing the AF stage to operate at
a low-distortion level of something like 1% of rated output.

73,

Chuck
NT3G

Thanks Chuck, forgot all about RSS 181, even though I have type approval
tested countless SSB transceivers to that specification. Interesting that
it has not been updated since 1971. Note that he sensitivity is defined as
that input that will produce 12 dB SINAD or that input which will produce at
least 50% of the rated audio output. The fact is that most of the testing
that I did was measured at full audio output, just below the threshold of
audio clipping. I do not recall any unit where the receiver gain was a
factor in sensitivity. Also note they still refer to "A3j", and not J3E,
etc. All these old specifications are based on tube designs. With TDA2002
type audio chips, you could typically get 5W out at 1% distortion. It was
so easy to drop in an extra IF stage if you could not meet the 50% min audio
output at threshold sensitivity.

73,

Frank