Re: 2.8kHz roofing filter

Posted by N5GE on Oct 23, 2010; 8:14pm
URL: http://elecraft.85.s1.nabble.com/2-8kHz-roofing-filter-tp5665995p5666301.html

On Sat, 23 Oct 2010 10:52:40 -0700 (PDT), ab2tc <[hidden email]>
wrote:

Hi Knut,

That adjustment should be made by adjusting for the offset of the
center frequency of the filter.  Even the 8 pole filters can be off by
a little and it's the most noticeable when switching sidebands.

Adjust the center frequency of the filter until you hear the same
pitch with both filters.

BT 73 ES GUD LUK
DE N5GE,
QCWA LIFE MEMBER 35102,
LICENSED SINCE 1976 AR SK

[hidden email]
http://www.n5ge.com

>
>Hello all,
>
>I recently replaced the 5-pole 2.7kHz roofing filter in my K3 with the
>8-pole 2.8kHz hoping to get rid of the difference in tonality between USB
>and LSB. But the difference is still there. These two links show the noise
>spectrum of the receiver in USB and LSB.
>
>http://ab2tc.getmyip.com:8000/pictures/usb.png
>http://ab2tc.getmyip.com:8000/pictures/lsb.png
>
>In USB there is a definite upward tilt of the passband and the opposite for
>LSB. This is quite audible. Is this normal and is there anything I can do
>about it (other than asking Elecraft to add by mode equalizer)?
>
>AB2TC - Knut

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