[TenTec] Questions about NR i.e. Orion

[Gary Hoffman]

Incidentally, I also have professional experience with adaptive noise
elimination.

I agree completely with the comments below.  Has nothing to do with
bandwidth as measured on a scope.

Obviously, we all know narrow filters help - a lot !

But in software, with enough processor, one can simply delete bits which are
noise bits, and leave in bits which are signal bits.  Then go through D to A
and one reconstructs the original signal, minus the noise.   Bandwidth
having nothing to do with it.

This works exceptionally well.

73 de Gary, AA2IZ


----- Original Message ----- 
From: <k6kdk at k6kdk.net>
To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
Sent: Thursday, March 23, 2006 5:22 PM
Subject: Re: [TenTec] Questions about NR i.e. Orion


> Ahhhh   Hummm... I agree w/ "Buck".. (speaking as a software-type here..)
a
> true NR system implemented in software is capable of "intelligently
> manipulating" noise and signal in a way that can not be detected on a
scope.
> It is fully possible (in software) to make determinations about which bits
> are noise which are information, pass and reject the bits on the fly,
> interpolate the intelligence through (create it artificially and insert it
> into the bit stream for later D/A) and a whole host of other "tricks" to
> improve intelligence throughput for a human user. You will never see this
> manipulatiuon on a scope no matter how hard you try.
>
> For some more informatiuon on these type of schemes see Flex Radio
> documentation on their site about what they call "NB2".  I mentioned
before
> on a previous post that I thought TT should outsource the NR to NCT
> Technologies who developed many such audio/ human listener NR codes under
> military contract. They now will license it out for a price.
>
> I don't want to bore you with recounts of my past victories in this realm.
> Nothing is worse than listenting to some retired software guy tell you how
> he could do it with one hand tied behind his back, but I once got paid a
> bunch to write just such code for a customer of ours that had severe noise
> (from RF interference) into a SMPTE time code track on his very expensive
> little black boxes. His boxes could no longer "hear" the information
stream.
> We cleaned that right up for him, no problem !
>
> 73s -Dan  K6KDK
>
> ==================snip=========================
> I submit the only way to check the NR function is by listening.  It
either
> works or it doesn't.
>
> It hasn't worked since version 1.371.
>
> K4ia  "Buck"
> Fredericksburg, Virginia USA
> ----- Original Message -----
> From: "Grant Youngman" <nq5t at comcast.net>
> To: "'Discussion of Ten-Tec Equipment'" <tentec at contesting.com>
> Sent: Thursday, March 23, 2006 9:36 AM
> Subject: Re: [TenTec] Questions about NR i.e. Orion
>
>
> > > MDS, S/N and similar measurements with NR on must be peformed
> > > completely with the signal present, and not by switching the
> > > signal on and off.
> >
> > > This means that the only way to do it is by spectral
> > > analysis, with due care paid to subtle issuses like windowing
> > > functions, bin size, etc.
> >
> >
> > I've been poking at NR on and off for a couple of days now on 2.032.
> Using
> > an Elecraft N-gen noise generator to a Daven RF attenuator (to control
the
> > fixed output of the N-gen), with an 8640B providing the signal, and both
> fed
> > to the radio through a TT 651 hybrid.  And watching the whole thing on
> > Spectrum Lab.  AGC off (really very fast), and the RF gain reduced
enough
> to
> > keep the signal out of the AGC range.
> >
> > With no signal present, NR drops the noise output to about -30dB
> (relative).
> > But the baseline noise level increases with the application of a signal
to
> > about -18dB.  NR drops both signal and noise level when turned on
relative
> > to the levels without.  The noise component in the passband is rolled
off
> > fairly gently by what appears to be a a very broad filter effect, so
it's
> > most likely that SNNR is increased, but I'm not sure how to measure it
> from
> > what appears on the display.  The signal peak actually seems to decrease
> by
> > 2-3 dBu relative to the noise at the baseline right in the vacinity of
the
> > signal, but there is noise rolloff above and I think below the signal
> > (although the lower side is harder to ascertain).  It shows up best if
> SPOT
> > is set relatively high, such as around 1 Khz.
> >
> > There is no indication of any very narrow or steep-sided bandpass filter
> > being applied, so the filter itself looks relatively simple and quite
> broad.
> > Actually, it looks much like what I see from a couple of external
> > audio-based DSP gizmos.
> >
> > My recollection of pre-1.372 NR performance, on SSB signals, is that the
> > high frequency rolloff in particular was possibly more pronounced.
> >
> > Grant/NQ5T
> >
> >
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> >
> >
>
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