Hi Kim,
Back in the spring, many of us posted here regarding the NR. As Grant
suggested,
you can check out the archives. There's good (historical?) information there.
The manual section regarding NR usage describes how to use the original NR
filter that was implemented by Doug Smith. That implementation is long gone, so
the text is non-applicable, for the most part.
Charles said:
> Under the same conditions when the NR is on
> in any position I have raspy CW reception. Do
> you experience the same with your Orion II NR?
>
> Charles, K0CW
Charles, tighten up the BW around the signal, especially if it is weak. I
believe the raspiness is the NR-created intermodulation product of the signal
and noise within the passband. The less noise power in the passband (smaller
bandwidth), the less intermod power produced.
Kim noted how keeping the BW below 1240 Hz helps for CW. I go to 500hz by
default and the weaker the signal, the narrower I make it.
Kim said:
> When I turn down the RF gain and crank the audio gain wide open
> (essentially using the RF Gain as the volume control) I can detect
> the superimposed noise at NR settings above about 5 at 600 Hz
> bandwidth. This effect vanishes when the bandwidth is set to ~400 Hz
> or less. That said, at such RF Gain settings I see no reason to use
> any NR because everything is pretty quiet.
The more aggressive the NR setting, the more non-linear it is, which increases
the intermodulation product power, so a narrower BW is needed.
In my opinion, the best way to use the NR for weak signals is to keep the BW
tight, as mentioned, (less than 600hz for CW and 2400 for SSB) and decrease RF
gain until the noise becomes noticeably attenuated. This is the point where the
NR creates the most difference between the signal and the noise. It is a
threshold area of sorts.
Good luck,
Lin
WB1AIW
Kim Elmore wrote:
> Honestly, I don't think there is a significant problem.
>
> Having fancied myself very picky about audio (I'm an amateur
> violinist and was a borderline audiophile -- or audiophool -- in the
> distant past), I just did a careful listen on some 40 m CW with both
> the speaker and good headphones.
>
> I have all the roofing filters installed, set for auto selection and
> my CW pitch is 600 Hz. RF Gain is 100, preamp off, binaural rx
> disabled, and sweep display both on and off. At bandwidths of less
> than about 1240 Hz, all CW signals are silky smooth. At bandwidths
> greater than 1240 Hz, I begin to detect some filter-imposed
> artifacts. The effect is dependent upon the filter setting: the more
> aggressive the filter setting, the more apparent the effect. Even so,
> I consider it minor. What I hear sounds a bit like the noise around
> the signal, but superimposed on the signal.
>
> However, at bandwidths less than about 1240 Hz, everything is simply
> silky smooth. I tend to run my bandwidth at 600 Hz. Yes, yes, I know:
> the 1000 Hz filter may be a better choice from a rx performance
> standpoint, but I like the "sound" at 600 Hz bandwidth.
>
> I tried everything again with binaural rx enabled and found myself a
> bit more able to detect the DSP artifacts, but I also became
> convinced that at higher RF gain settings, the effect seemed to
> disappear (I find myself more able to hear noise in stereo than in
> mono. For me, stereo noise tends to have the aural effect of physical
> width -- this may not be true for everyone).
>
> When I turn down the RF gain and crank the audio gain wide open
> (essentially using the RF Gain as the volume control) I can detect
> the superimposed noise at NR settings above about 5 at 600 Hz
> bandwidth. This effect vanishes when the bandwidth is set to ~400 Hz
> or less. That said, at such RF Gain settings I see no reason to use
> any NR because everything is pretty quiet.
>
> So there you have it: while I could detect some DSP NR artifacts
> under certain conditions, those conditions are currently outside of
> my operating envelope. I don't think the "problem" is significant.
>
> Kim Elmore, N5OP
>
> At 12:19 PM 12/4/2006, you wrote:
>
>>Charles and Kim,
>>I have a new O II, current firmware, purchased from TenTec about a month
>>ago. I also have experienced the same phenomenon with the DSP NR.
>>Regardless of signal levels, Atten, RF Gain, and Audio settings.. even with
>>DSP at 1.. a CW signal becomes distorted when enabling DSP NR.
>>
>>Seeing that CW is virtually my only mode of operation, it is somewhat
>>disquieting, pun intended, that an advertised feature doesn't function. I
>>called TenTec and spoke, briefly, to someone in their 'service' department,
>>about the malfunction. I received a rather gruff and abrupt, "There's
>>nothing wrong with the Orion, read the owner's manual, goodbye."
>>
>>If you gentlemen come up with a set of control parameters that allow the use
>>of DSP NR with CW, please post your solution.
>>
>>Thanks and 73,
>>Emil
>>W9NM
>>
>>
>>
>>Kim,
>>
>> Under the same conditions when the NR is on in any position I have raspy
>>CW reception. Do you experience the same with your Orion II NR?
>>
>>Charles, K0CW
>>
>>Kim Elmore <cw_de_n5op at sbcglobal.net
>><http://lists.contesting.com/mailman/listinfo/tentec> > wrote:
>> I have the O II, 2.037J firmware. The manual says that different
>>noise reduction settings affect how long the DSP takes to decide
>>what's nose and what's signal, but that the end result is the same. I
>>thought this odd, because it seems there's no point in using anything
>>but the "fastest" setting.
>>
>>In playing with it on CW, this doesn't appear to be the case:
>>different settings definitely result in different amounts of noise
>>reduction, and the lower settings seem to do their job immediately,
>>but not as aggressive as the higher settings. Intuitively, this is
>>what I'd expect.
>>
>>Has the NR changed in later firmware versions and the manual failed
>>to keep? Or, has the manual always been in error?
>>
>>Cheers,
>>
>>Kim Elmore, N5OP
>><<<<
>>
>>
>>
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>
>
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