Re KH7T's post on NB vs. NR reproduced below:
If John's informative discussion results from my post and following
discussion, I want to specify: There is no confusion at K6XT regarding
the difference between these 2 functions. On my O1 the NB works just
fine when I have the rare occasion to need it at my rural, largely
vertically-polarized-impulse-noise-quiet location with the occasional
electric fence pulses.
The NR so far leaves much to be desired and, I say again, is
significantly less effective than my Timewave DSP59+ (which has no NB
function at all). The Orion NR function inhibits good copy on weak
signal narrowband filter settings. I refer only to CW as I have no
experience tuning fone. Oddly, on my O1, even strong signal fidelity is
reduced because noise is somehow "added" to the signal with NR turned on
whereas the "added" noise is absent with NR turned off. Most intriguing.
I continue to experiment with AGC settings to see if AGC has something
to do with this. I want to thank K7HP for his information and
measurements. Hank implied that apparently there are 2 AGC loops, one of
which is not disabled when we users set AGC OFF. Listening to strong EU
stations on 40 CW this evening I confirmed that turning AGC off seems to
have little effect on the quality and quantity of volume. This is an
unexpected result. Traditionally, turning AGC off in the presence of
strong signals will overload either the ears or the receiver. But it had
no effect on the strong signals I was tuning, implying that the AGC OFF
setting isn't.
73 Art
k6xt at arrl dot net
tentec-request@contesting.com wrote:
> Today's Topics:
>
> 1. 285, 288 Filters FS (PaulKB8N@aol.com)
> 2. Wanted: Orion II (Ed Cummins)
> 3. Re: Orion NB vs NR (John Buck)
> 4. Re: Wanted: Orion II (ron)
> 5. Re: Wanted: Orion II (EI6DL)
> 6. Re: Orion NB vs NR (Gregory J. Knapp)
> 7. Re: [Orion] Orion NB vs NR (Pfizenmayer)
> 8. SOLD = Idiom SCAF (W.D. (Doc) Lindsey)
> 9. encoder for Omni VI (Paul DeWitte K9OT)
> 10. FS or Trade, Model 238, 229 tuners (George R. Griesbach W5GRG)
> 11. Re: 301 remote tuning knob (Dave Edwards)
> 12. TenTec Orion I V2 (Bernhard Hoidn)
> 13. V2.056 (jalankfor@linxure.net)
>
>
> ----------------------------------------------------------------------
> [Snip]
> ------------------------------
>
> Message: 3
> Date: Thu, 05 Oct 2006 08:44:26 -1000
> From: John Buck <kh7t@arrl.net>
> Subject: Re: [TenTec] Orion NB vs NR
> To: Zenvrim@aol.com
> Cc: Orion@contesting.com, tentec@contesting.com
> Message-ID: <4525528A.4040001@arrl.net>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> It seems that a lot of people confuse noise Blanking and Noise Rejection.
>
> NOISE BLANKER (NB)
> My NB is extremely effective on ignition noise and my neighbor's weed
> eating electric fence. The S9+ fence disappears and with not much
> distortion.
>
> I am not sure what the difference between the so called Hardware and the
> Software options are, but sometimes one seems to work better than the
> other. NB is effective against very short impulse type noise that can
> be somewhat irregular. NB does not work on band noise but does
> sometimes help static crashes.
>
> Usually older hardware implementations have a separate wide bandwidth
> detector near the front of the receiver and if an impulse is detected, a
> switch shuts off the signal path near the front end for a short period
> of time. In effect, it puts a hole in the signal reception to prevent
> the pulse from getting spread by the narrow band filters and detectors.
> If a system has sufficient dynamic range to not be saturated by the
> impulse then the impulse can be identified in one signal path and used
> to blank a second delayed signal that you then use for detection. This
> approach can completely remove the short impulse from the signal you hear.
>
> It works very well. Sometimes my electric fence is S9+. The NB makes
> it disappear into the S1 to 3 background. I often have to set it at 8
> or 9. The Orion V2.059d is better than my K2 and that is pretty good.
>
> NOISE REJECTION
> The Noise Rejection is an attempt to remove background noise and
> everything else that is not signal. There are many different algorithms
> for this. It works better if the bandwidth is set larger than the
> signal bandwidth so the algorithm can get a grip on the noise in order
> to remove it.
>
> It is not just a BW reduction approach although sometimes it sounds that
> way. TT has tried several different schemes. I am not sure how the
> current approach works on cw. It works quite well on weak SSB and often
> makes an unreadable signal pop out of the noise, although it sounds a
> bit distorted. I am not sure that it works that much better than
> adjusting the threshold and Bandwidth just right but it is a lot quicker.
>
> NR does not work on impulse noise and other stuff that may saturate the
> filters or detectors.
>
> I like the idea of identifying the noise and subtracting it from the
> signal. I think it works and will work better in the future. I thought
> it worked better on a earlier version but it worked poorly on some of
> the interim versions. It is better now in V2.059d but more distortion
> than I like on SSB.
>
> Aloha,
> John KH7T
>
> [Snip]
>
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