TopBand: RX AID FROM THE PAST

[Bob Eldridge]

>stereo headphones (or two speakers) with the "lowpass" audio feeding
>one ear and the "highpass" audio feeding the other.  Supposedly, ...

Not just supposedly! The idea works. The Hildreth filter does exactly that,
and is very useful. It also has variable gain on each channel, and a control
to 'mark' the crossover frequency (the one in the middle of your head) with
a 90Hz buzz, and a control to introduce a variable level of white noise.
Used on SSB it can compensate for excessive bass or treble, remove some of
the effects of overcompression, noise below between and above the voice
formants....

Unfortunately Don Hildreth ceased production several years ago, but
published full details of the designs in Ham Radio Magazine Sept 1985 (CW),
January 1980 (SSB) and there are relevant articles in November 1976,
November 1975, December 1986, June 1983.

G's will recognize it as the concept of G6CJ's 'Stereocoder' and updates
explored in RadCom.

Bob VE7BS



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