[HBR] El-Cheapo (and El-SIMPLO!) CW Filter

[Tim Shoppa]

K5MO writes
>> (Eddy writes of 88mH toroids)
> Eddy....where do you find the toroids!?

22, 44, 88 mH toroids used to be extremely common telco surplus things.
They were used to compensate for loading on long telephone lines.

Most modern audio-filter designers who need similar range toroids today
(look at the fancy stuff that folks do with single-signal direct conversion
receivers, for example!) use ferrite bobbin-core inductors, look up Digikey
RL622-823K-RC for example. They do not have spectacular high Q's
but I for one much prefer a not-high-Q audio filter over a high-Q with
its horrible horrible ringing.

Some folks combine simple electronic audio filters with a tuned speaker
for very good and very listenable CW, e.g.:

  http://www.io.com/~n5fc/res_spkr.htm

The writer there has a lot of the same feelings I do about
super-high Q filters and how they can easily decrease the
listenability of CW (personally I feel his 35Hz bandwidth is way
too narrow for my ears, though!)

Tim N3QE