[Elecraft] Low Frequency Modulation of Side Tone.

[Bill Coleman]

On Jan 23, 2005, at 10:30 PM, W3FPR - Don Wilhelm wrote:

> For a source of decent audio transformers for low power applications 
> like that, look at defunct computer modem cards.  I have salvaged 
> transformers from them for computer to audio equipment isolation for 
> some time now - small and quite inexpensive (i.e. 'cheap', 'free', 
> etc.)

I'll second this. In fact, if you can find an older Hayes modem, like 
one of the 2400 bps full-sized modems -- the transformers are very high 
quality. They are physically large, about  3cm on a side and 1cm high 
(for through-hole board mounting). Hayes persisted in using these large 
transformers for years because they provided a low-distortion coupling 
to the phone line.

Some of the teeny 1cm cube transformers you find in cheap modems aren't 
nearly as nice, but will work as well.

Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr at arrl.net
Quote: "Not within a thousand years will man ever fly!"
             -- Wilbur Wright, 1901