[TenTec] Orion II NR Performance Measurements

[Duane A Calvin]

Try something that several of us here tried over the weekend - Turn NR
off, find a weak, at the edge of the noise CW signal, zoom in him with
the BW at 100.  Now, go adjust your filter taps from 199 down to
something around 120.  Voila.  If you watch it on a spectral display, the
passband becomes "flatter" and wider, but with sharp skirts.  But the
signal now becomes more audible against the noise.  This was a surprise
to me, but it was repeatable on several signals.  (If you run the taps
any lower than 122 on our Orion I's, the bandwidth control would cause
all sorts of strangenesses, essentially opening all kinds of strange
passbands in different places.  I have to write that one up for
Ditsnbits.)

        73,  Duane


On Sat, 25 Mar 2006 22:17:44 -0600 "Grant Youngman" <nq5t at comcast.net>
writes:
> 
> 
> I won't bore you with the setup here, but will be happy to provide 
> details
> to anyone who is interested.  Consistent results were obtained by 
> two
> independent methods: (1) graphical computation of SNNR, and (2) 
> spectral
> analysis software that directly computes an estimate of SNR.
> 
> The results are as follows (LCW, 1000Hz spot tone, NR=9)  
> 
> BW=3000Hz: SNNR improves by approx 1dB with NR=9.
> 
> BW=500Hz:  SNNR degrades by approx 2dB with NR=9.
> 
> There is improvement at 3 Khz bandwidth, but it's negligible.  At 
> 500 Hz
> (and anything below that as well) you're better off without NR at 
> all.  The
> distortion created by NR at any bandwidth in both CW tone and SSB 
> voice is
> very unpleasant compared to typical noise reduction products. 
> 
> Even without having a v1 Orion to compare with I'm basically moving 
> from the
> "uncertain" bench to the "put it back the way it was" bench.
> 
> Grant/NQ5T
> 
> 
> 
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> 


--------------------------------------
Duane Calvin, AC5AA
Austin, Texas

http://home.austin.rr.com/ac5aa