One of the cheapest add-ons for any ham radio is opening
the mono audio to binaural. Stereo headphones are standard to-day.
A small box is easy to put in between rig and phones.
Our best computer is between our own ears. This "machine " works
in molecular level.
In headphones we need phase difference to simulate free sound between ears.
A simple RC network LoPass and Hipass can give a smalla idea, and is
easy to make.
The same question was solved in TV receiver. In mono audio days a special
"Pseudo Stereo" technique was used to open mono channel to Pseudo or
Spatial Stereo.
Pseudo keeps bot L and R channel amplitudes the same, but plays with
phase difference. Low frequency difference is 0 with increasing to
600-800Hz.
Advantage; this is good for SSB, too.
A special IC TDA 3810 from Philips or Signetics is still somewhere
available.
Data sheet gives the ideas and schematics, look
www.datasheetcatalog.com
TDA is the easiest way, byt same can be done with usual OpAmps.
Google "pseudo stereo" and find how audio specialists use this to-day.
There is even a PC program to play with:
www.multitrackstudio.com/pseudostereo.php
My experience; the world is never the same thereafter.
I have used my small unit for 20 years now.
Pseudo Stereo can be built-in K2 or K1. With TDA3810 and two small 100mW
amplifiers the
current increase is not much.
Or make it outboard to leave your rig unmodified and minimalized.
The best place is after all filtering and digital noice reductions. This
means
the easiest place, phone plug.
Benny oh9nb
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