K3 NR
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I have read the discussion on K3 noise reduction with
interest. I believe the best SSB noise reduction can be found on the
Omni VII. SSB signals on the Omni VII stand out and sound very good with
no harshness while giving the appearance of reducing the background noise.
NR on my Omni VII is so good I can leave it on all the time without
compromising the quality of the signal. I find objectionable resonances
when using NR in SSB mode on my K3. The best way for me to minimize these
resonances is to use the SHIFT/LO. Apparently NR is best used in the CW
mode on the K3. Conversely, NR is somewhat mushy in the CW mode on the
Omni VII. I guess you can't have it both ways. It may be an AGC
thing. Roy Morris W4WFB
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> I have read the discussion on K3 noise
reduction with interest. I believe the best SSB noise reduction can
be found on the Omni VII"
It's interesting to hear the differing opinions on
this subject. While I found the NR on the O7 to be good, it wasn't
exceptional. I thought the NR function attenuated the desired signal, even
at the least aggressive setting.
The best DSP NR I've heard came from the Omni 6+ as
well as the LMS algorithm used in the W9GR DSP box. Both DSP NR occurs in
these devices at the AF level, rather than I.F.
Just curious, does the K3 implement a true LMS
algorithm at I.F. in one of its menu-selected NR routines? Lyle?
I've never been too impressed with some of the other "contour optimized"
NR routines like that used in the FT-1KMP series.
Paul, W9AC
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> Just curious, does the K3 implement a true LMS algorithm...?
Yes, the K3 NR implements the "Leaky" LMS algorithm. There are other NR algorithms, and each has strengths and weaknesses, proponents and detractors. 73, Lyle KK7P _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by P.B. Christensen
It's remarkable how on any list for any radio, NR is the bugaboo. Everyone expects magic. There ain't no stinkin' magic. To Bill's point, it is far less effective -- to the fact of almost being unnoticable at relatively narrow CW bandwidths.
Having used virtually every 3rd party box known to man in the search for nirvana, and been in on much of the use, discussion and some analysis of another high end radio's NR function, I find the K3 NR to be extremely effective on SSB and CW, when the conditions (be they band or radio settings) are right for NR to be effective, which they are not always. As for the conjuration of it all, it's just dynamic filtering, not something mystical (that is what at LMS algorithm does -- there's nothing mystical about LMS, either). Grant/NQ5T
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I find the K3 NR to be rather good, but what
strikes me the most is how I can't find a favorite setting, but I always have to
go through the available settings to find something that suits a given signal.
That would suggest that even more settings could be useful, if they bring
anything new to the table. I have to say that I have been rather impressed
listening to sample files from BHI LTD:
If I am not mistaken, I think some time ago I saw
some of their promotional materials boasting that they used an algorithm based
on neural networks. It would be interesting to know if such an approach can be
shown to be equivalent to the approach used by Elecraft, or if it offers a
useful variation.
Another thought: Many noise reducers including the
K3's do seem to attenuate the high frequencies, sometimes just slightly and
sometimes excessively. Much of what we perceive as irritating noise seems
to be in the higher frequencies, and just cutting those off using bandpass or
equalizer might have a similar effect. To make it easier to determine whether a
particular NR setting is useful, it might be helpful if each of the settings
would include filtering that would emphasize the highs to compensate for the
highs lost in NR. I am guessing that the effect of the NR would then
appear more subtle, but also more honest. Of course the design parameters
might not easily translate to the effect of audio frequency response, and that
response may vary with the momentaneous characteristics of the wanted signal and
the noise, but at least it should be possible to measure the signal and noise
characteristics in real time.
73,
Erik K7TV
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To be more clear: While we cannot measure the
original signal independently of the noise, the processed signal's
frequency content can be determined (I am assuming voice), and if it is lacking
in highs compared to an average human voice then the processing could be made to
crank up the highs. I think the algorithm could automatically determine the
general pitch of the voice (such as male vs female) and vary the adjustment
accordingly. Of course this would not fit every voice with a given general
pitch, and the user could be given various settings with different amounts of
high emphasis, that would be parametric based on the general pitch (not like the
existing equalizer).
73,
Erik K7TV
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