[TenTec] Questions about NR i.e. Orion

Thu Mar 23 21:07:45 EST 2006

Gary,
I'm interested in learning more about this technique. Can you recommend any 
reference material on the subject?

Thanks,
Lin
WB1AIW

Gary Hoffman wrote:

> 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
>>>
>>>
>>>_______________________________________________
>>>TenTec mailing list
>>>TenTec at contesting.com
>>>http://lists.contesting.com/mailman/listinfo/tentec
>>>
>>>
>>
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>>
>>
> 
> 
> 
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