[TenTec] Questions about NR i.e. Orion

Fri Mar 24 23:31:37 EST 2006

Much obliged,
73,
Lin

Gary Hoffman wrote:
> Lin,
> 
> There are many excellent references available, but some of them make for
> very dense reading.  Some of the more basic stuff can be found in Technical
> notes published by Bruel and Kjaer Instruments some years ago.  Although
> they specialized in audio work, it is the same principle, and the Orion's IF
> is low enough to apply these same techniques obviously.  I will try and see
> if I have these on the shelf someplace, and can either cite them, or perhaps
> scan them into the computer.
> 
> 73 de Gary
> 
> ----- Original Message ----- 
> From: "Lin Davis" <linbdavis at earthlink.net>
> To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
> Sent: Thursday, March 23, 2006 9:07 PM
> Subject: Re: [TenTec] Questions about NR i.e. Orion
> 
> 
> 
>>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
>>>>>
>>>>>
>>>>>_______________________________________________
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>>>>>TenTec at contesting.com
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>>>>>
>>>>>
>>>>
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>>>>
>>>
>>>
>>>
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>>>
>>
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> 
> 
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