Re: K2-CW-Filter-Response: is that ok?

Posted by Vic K2VCO on Apr 26, 2005; 5:25pm
URL: http://elecraft.85.s1.nabble.com/K2-CW-Filter-Response-is-that-ok-tp377646p377647.html

Karsten Eppert(DK4AS) wrote:

> I have set the wide CW-Filter (Fil1) to 1,5 and aligned the BFO to a
> pitch of 700 Hz. I applied HF of constant frequency to the
> receiver-input with a signal strength that generated S9+10 db max. and
> plotted the S-meter versus variation of the VFO from high pitch to low
> pitch in 100 hz-steps. So I could determine a filter-curve. What strikes
> me is, that even at very low pitch-frequencies there is hardly
> attenuation and even at zero beat the S-meter still shows approx. S3.
> Turning the VFO "behind" zero-beat lets the S-meter decrease but it
> takes another 300 Hz until S0 is reached. The tone of the "wrong"
> sideband remains audible at even higher frequencies.

There's probably nothing wrong with your filter.  If you wish to have a wide CW
filter setting, you should locate the BFO during the CAL FIL adjustment so that
the filter passband is higher with respect to zero beat.  If you use Spectrogram
-- see <http://www.n0ss.net/index.html#Spectrogram> -- you can see this graphically.

With correct adjustment, you should not hear any signal on the 'wrong' side of
zero beat.

--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco

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