Sending this again.. I think I used wrong address before.
The venerable Ten-Tec audio CW filter is based on 741 op amps, I believe and
has two widths.
The version of this I saw in a QRP Projects book (ARRL) has 4 widths as I
remember. I cannot find that exact book on the shelf right now. In my
mind/memory it was distinguished by the larger number of available widths.
The MFJ CWF filters had 3 widths available switchable - 180, 110 and 80 (seems
narrow to me) - so it says on the front of the filter box.
This is also outlined on Page 82 of Solid State Design for the Radio Amateur.
This is a version of same, or pretty darn close:
http://www.k4icy.com/cwfilter.htm
I suppose at one time I would have liked more widths.. probably now I would be
happy with two and just a way to switch in/out for full or filtered sound.
Brian VE3VAW
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