NR comment and roofing filter questions

[Douglas G. Bonett]

I am still learning about all the features in my K3/10 (#1213, ordered 2/19/08,
received 7/11/08).  It has the 2.7 kHz filter and no options.

I agree with others that the K3 NR can be improved.  I resorted to using an
outboard DPS filter, the ADSP2 from SGC. The ADSP2 works great on CW but I don’t
like how it distorts voice.  The ADSP2 must use a very different algorithm than
the K3 NR because NR takes out noise the ADSP2 leaves behind and the ADSP2 takes
out noise that NR leaves behind and this seems to hold for all bands and all
band conditions. I’m still playing with different setting to get NR to sound
good with voice but so far the NR in my Omni VI seems to work a little better
with voice because the Omni NR does not distort voice as much. I do not have a
Clear Speech now, but when I did have one I liked the way it worked with voice
by reducing the noise and not distorting the voice.  The Clear Speech was not
good for CW as I recall.  Maybe Elecraft will figure out how to modify NR to
make it work more like the NR + ADPS2 combination when in CW mode and more like
the Clear Speech when in SSB mode.

Given the inability of NR to reduce noise in CW as much as I would like, I
wonder if a narrower roofing filter might knock out a certain type of noise that
NR can’t eliminate. I don’t need a narrower roofing filter to handle very strong
and very close signals, but I wonder if the narrower roofing filter cuts out
some noise that the NR leaves behind (similar questions have asked on this
reflector but I can’t find a satisfactory answer). Could someone at Elecraft
please perform a very simple experiment for me?  Have two K3s running side by
side. Put only a 2.7 kHz filter in one and put 2.7 and 1.0 kHz filters in the
other. In CW mode, set BW to about 600 Hz and engage NR. Set the volume the same
in both rigs and tune both rigs to the same unoccupied frequency of a noisy
band. Does the K3 with the 1.0 kHz filter sound less noisy and less fatiguing?

I have a second question out of pure curiosity. Can someone at Elecraft give me
a rough estimate of the 2 kHz IMD with only a 2.7 kHz filter? I would be happy
to hear Eric’s best guess subjective/conservative estimate. I realize this value
was reported in a recent RadCom article but the results reported in that article
are so unbelievable that I suspect there was serious problem with the testing
procedure.

N0HH


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[Brett Howard]

Not really...  The DSP does a VERY good job cutting out the noise in
absence of strong nearby signals.  I have the 2.8/1.8/1.0/250 Hz
filters and in a clean band I can't tell much difference at all when
they are on/off.

On Sun, Aug 24, 2008 at 4:53 PM, Douglas G. Bonett <[hidden email]> wrote:

> I am still learning about all the features in my K3/10 (#1213, ordered 2/19/08,
> received 7/11/08).  It has the 2.7 kHz filter and no options.
>
> I agree with others that the K3 NR can be improved.  I resorted to using an
> outboard DPS filter, the ADSP2 from SGC. The ADSP2 works great on CW but I don't
> like how it distorts voice.  The ADSP2 must use a very different algorithm than
> the K3 NR because NR takes out noise the ADSP2 leaves behind and the ADSP2 takes
> out noise that NR leaves behind and this seems to hold for all bands and all
> band conditions. I'm still playing with different setting to get NR to sound
> good with voice but so far the NR in my Omni VI seems to work a little better
> with voice because the Omni NR does not distort voice as much. I do not have a
> Clear Speech now, but when I did have one I liked the way it worked with voice
> by reducing the noise and not distorting the voice.  The Clear Speech was not
> good for CW as I recall.  Maybe Elecraft will figure out how to modify NR to
> make it work more like the NR + ADPS2 combination when in CW mode and more like
> the Clear Speech when in SSB mode.
>
> Given the inability of NR to reduce noise in CW as much as I would like, I
> wonder if a narrower roofing filter might knock out a certain type of noise that
> NR can't eliminate. I don't need a narrower roofing filter to handle very strong
> and very close signals, but I wonder if the narrower roofing filter cuts out
> some noise that the NR leaves behind (similar questions have asked on this
> reflector but I can't find a satisfactory answer). Could someone at Elecraft
> please perform a very simple experiment for me?  Have two K3s running side by
> side. Put only a 2.7 kHz filter in one and put 2.7 and 1.0 kHz filters in the
> other. In CW mode, set BW to about 600 Hz and engage NR. Set the volume the same
> in both rigs and tune both rigs to the same unoccupied frequency of a noisy
> band. Does the K3 with the 1.0 kHz filter sound less noisy and less fatiguing?
>
> I have a second question out of pure curiosity. Can someone at Elecraft give me
> a rough estimate of the 2 kHz IMD with only a 2.7 kHz filter? I would be happy
> to hear Eric's best guess subjective/conservative estimate. I realize this value
> was reported in a recent RadCom article but the results reported in that article
> are so unbelievable that I suspect there was serious problem with the testing
> procedure.
>
> N0HH
>
>
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> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
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>
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>

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