FROM: http://web.telia.com/~u85920178/use/filt2.htm

FROM: http://www.appliedphysicstech.com/CWF.html
CWF-001 Active CW Filter

FROM: http://www.morsex.com/misc/filter.htm
Vectronics CW Filter Kit with 1W Audio Amp

FROM: http://www.hanssummers.com/radio/cwfilter/index.htm
http://downloads.hanssummers.com/cwfilter.pdf
Phase-Shifting CW Filter by Radio Society of Great Britain


FROM: http://midnightscience.com/kits.html

HI-PER Audio Filter: 200 Hz wide; centered at 700 Hz Gausian active filter
with minimal group delay...no ringing... I have used this filter for over a decade
and it is very good with qrq cw. It is to be placed just before the final audio amp.
Please see the attached PDF file for the full article about it.

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If you would like to share your favorite cw filter please feel free to upload some images and descriptions by clicking on the 'Reply to This' tab underneath the CW FILTER SHOWCASE ARTICLE. (The green rectangle in the "REPLY" menu bar will add pictures.)
http://newenglandqrp.org/nescaf

see eHAM reviews of this filter HERE

DELUXE COMMUNICATIONS AUDIO BOARD by David Curry wd4pli

This is one of the best external Audio filters with a very clean amp and lots of excellent features:
Q-mulitplier
notch filter
cw regeneration
variable bandpass


see PDF file for full article

Attachments:
PASSIVE CW FILTER KIT from Xtal Set Society, Inc

This filter was easy to build from a kit, and has a very effective bandpass design for cw.
Please click on the attchment WAVE FILE to hear this filter in action.

Attachments:

THE NEW HI-PER-MITE CW BANDPASS FILTER 

 UPGRADED DESIGN   -  SEE WEBSITE FOR MORE INFO  

http://www.4sqrp.com/HiPerMite.php

Here is a spectrum view of the bandpass of this filter for 700 hertz center frequency

Here is the view of the waveform sweep in AUDACITY

Here is what it sounds like sending cw dits from 300 hertz to 1200 hertz

Here is an audio example of how well the HI-PER-MITE filters a harsh square wave sidetone

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