On studying my Extra Class License manual, I ran across the schematic and
description of an active RC bandpass audio filter. I was just wondering if
I could install this filter between my headphone jack and my headphones for
a quick and dirty cw filter.



--
Lee ki6azs

Hi Lee...

Why not?

Three suggestions I might make;

- Be sure that the input/output levels and impedance are those of the
headphone circuit. I would surmise that most designs you come across
would be made for lower signal levels than those found at the audio o/p.

- Delve into the bandwidth requirement for CW listening and dont
discount the brains ability to do better extracting the signal from a
wider bandwidth. ie you might think that it is worthwhile using (say) a
50Hz wide filter for CW but you'll find it harder to decode in your head
than using something wider.

- If you want to experiment with what b/w to use, record some CW on your
computer and use an audio processing program to build some LPF and HPF
filters. Audacity is a possibility. You could of course simply make an
adjustable hardware filter instead!

Cheers Bob VK2YQA

lkokot wrote:
On studying my Extra Class License manual, I ran across the schematic and
description of an active RC bandpass audio filter. I was just wondering if
I could install this filter between my headphone jack and my headphones for
a quick and dirty cw filter.

Thanks for suggestions, Bob. the design in the manual includes a
potentiometer for adusting bw. How effective it is, I don't know. I
guess I will breadboard it and see what transpires. 73.

lee ki6azs