[CW] Audio "System" for CW notes?

[David Ring]

I have always found that speakers such as the ones in the following
links are excellent.  They are like a pipe organ pipe - resonant and
the signals just pop out of the noise even with wide (2.1 kHz or more)
selectivity.

This one is just text - but has the formulas for frequency resonance.
http://www.qsl.net/we6w/projects/Res_spkr.txt

http://kd1jv.qrpradio.com/resonatespkr/CWSPKR.HTM
http://www.io.com/~n5fc/res_spkr.htm
http://www.qsl.net/n5iw/RESONANT.htm
http://www.qsl.net/kd7rem/resospkr.htm

73

David, N1EA
-30-