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

[Grant Youngman]

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