[TenTec] Some NR Performance Measurements on the O-II

[Douglas Shock]

I think you nailed in Grant. RF gain set to 100. I agree that NR works very
well at this setting but as you reduce your RF gain, the NR begins to
distort. So, there appears to be a direct relationship between these two
settings.

Leave the rf gain alone and NR works wonders and this is the case for CW as
well.


On 3/12/06, Grant Youngman <nq5t at comcast.net> wrote:
>
> Very noisy band conditions here tonight, with storm noise in the area --
> lousy band conditions overall, and propogation seemed to be off, with many
> of the usual big gun signals not up to par.
>
> I set out to measuring the improvement in apparent (S+N)/N ratio
> attributable to NR.  What I found was an improvement of at least 10-12dB
> on
> weak SSB signals at 2.4 Khz bandwidth, RF gain wide open.  AGC was set to
> Fast -- tried it at other settings, including Off, but it didn't
> materially
> change the result.  At the Fast AGC setting, however, there was much less
> distortion on weaker signals with NR since static crashes didn't hang the
> AGC.
>
> A typical scenario went something like this -- adjust receiver output for
> roughly 0dB reading on output meter with no signal present.  The signal
> would drive output to perhaps 1-3 dB on voice peaks.  Then turn on NR (9),
> reset baseline noise-only reading to zero as above by increasing the audio
> gain. The signal would then peak to 13-16dB on output meter.  Admittedly a
> rough measurement, but the average improvement was consistent on a variety
> of signals checked.
>
> I consider this level of improvement in SNR pretty respectable on an SSB
> signal, given the noise characteristics tonight.   I plan to make some
> more
> measurements tomorrow when 20 opens up on both SSB and CW.  The noise
> conditions should certainly be better.
>
> Grant/NQ5T
>
>
>
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