K3 filter problems

[Jim Hoge]

Greetings,

 

I seem to have a problem with either how I set up my K3 or with the filters. When first built  the radio, I had only the stock 2.7 filter in it. I noticed that the receive audio began to ring and sound hollow when the bandwidth was reduced to about 1K. I now have the 1K filter in position 3 and the 400Hz filter in position 4. (I may add a narrow phone filter in the future in position 2.) Filter widths are configured at 1K and 400 respectively. All filters are enabled for both cw and digital. I note that the filter in use does coincide with selected bandwidth but again, as I narrow down to 1K or tighter, the received sound is still hollow and ringy. BTW, only the 400 Hz filter has gain added in the configure menu to offset its loss. Have I done something wrong?

 

Tnx,

Jim W5QM

#1816

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[Don Wilhelm-4]

Jim,

I am not certain what you are calling "ring and sound hollow", but on my
K3 I can hear what I believe is audio limiting on strong signals - it
happens on both SSB and CW and has nothing to do with the filters (I
have only the 2.7kHz).  I believe the cure in my case is the AF mod, but
I have not yet installed it.  You might want to consider that mod to see
if it makes any difference.

73,
Don W3FPR

Jim Hoge wrote:

> Greetings,
>  
> I seem to have a problem with either how I set up my K3 or with the
> filters. When first built  the radio, I had only the stock 2.7 filter
> in it. I noticed that the receive audio began to ring and sound hollow
> when the bandwidth was reduced to about 1K. I now have the 1K filter
> in position 3 and the 400Hz filter in position 4. (I may add a narrow
> phone filter in the future in position 2.) Filter widths are
> configured at 1K and 400 respectively. All filters are enabled for
> both cw and digital. I note that the filter in use does coincide with
> selected bandwidth but again, as I narrow down to 1K or tighter, the
> received sound is still hollow and ringy. BTW, only the 400 Hz filter
> has gain added in the configure menu to offset its loss. Have I done
> something wrong?
>  
> Tnx,
> Jim W5QM
> #1816
>
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[AC7AC]

CONTENTS DELETED

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[Matt Zilmer]

All,

The 400 Hz and 1 KHz filters are 8 pole.  The offsets (should) be
zero.

matt

On Sun, 23 Nov 2008 18:23:12 -0800, you wrote:

>Whenever you reduce the bandwidth, you restrict all the audio you hear to
>that bandwidth. Make the filter narrow enough, and the only sound you hear
>will be one tone, and it won't go on and off any more  than the tone of a
>bell does (i.e. it rings  like crazy).
>
>
>
>There is no "magic" solution to that - restrict the bandwidth and you
>stretch the dits and dahs of CW out over time. It's all a matter of filter
>sharpness or "Q".
>
>

>Okay, with that background (forgive me if it's very old news to you, Jim), 1
>kHz isn't very narrow. So what could be producing a narrower bandwidth? My
>first thought is that you're crystal filter (the roofing filter) is not
>centered on the DSP filter bandwidth, so the effective bandwidth is much
>narrower than 1 kHz.
>
>
>
>If you used the 5-pole filters, did you input the offsets for the 1K and 400
>Hz filers correctly (including the minus sign ahead of the offset)? If not,
>you might have just part of the filter bandpass reaching the DSP, producing
>a total bandpass only a fraction of 1 kHz.
>
>
>
>Ron AC7AC
>
>
>
>From: [hidden email]
>[mailto:[hidden email]] On Behalf Of Jim Hoge
>Sent: Sunday, November 23, 2008 2:40 PM
>To: [hidden email]
>Subject: [Elecraft] K3 filter problems
>
>
>
>
>Greetings,
>
>
>
>I seem to have a problem with either how I set up my K3 or with the filters.
>When first built  the radio, I had only the stock 2.7 filter in it. I
>noticed that the receive audio began to ring and sound hollow when the
>bandwidth was reduced to about 1K. I now have the 1K filter in position 3
>and the 400Hz filter in position 4. (I may add a narrow phone filter in the
>future in position 2.) Filter widths are configured at 1K and 400
>respectively. All filters are enabled for both cw and digital. I note that
>the filter in use does coincide with selected bandwidth but again, as I
>narrow down to 1K or tighter, the received sound is still hollow and ringy.
>BTW, only the 400 Hz filter has gain added in the configure menu to offset
>its loss. Have I done something wrong?
>
>
>
>Tnx,
>
>Jim W5QM
>
>#1816
>
>

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