[TenTec] Noise Reduction Setting

[Kim Elmore]

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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