[Elecraft] K3 filter problems

[Ron D'Eau Claire]

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: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Jim Hoge
Sent: Sunday, November 23, 2008 2:40 PM
To: elecraft at mailman.qth.net
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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