[Elecraft] [K3] NR comment and roofing filter questions

[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 <dgbonett at iastate.edu> 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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