[Lowfer] Phasing exciters

[Stewart Nelson]

Hi all,

Generating a 90 degree phase shift (mathematically) is easy.
Google for "Hilbert transformers" and you'll see lots of
examples.  The first hit,
http://www-users.cs.york.ac.uk/~fisher/mkfilter/hilbert.html
has a form that will generate the code for you.

However, getting the phase shifted samples to the sound card
is very hard (for me, because I'm not a Windows wizard).

Three options:

If your application is not real time, e.g. a beacon, and the
Tx software can write a .wav file, you can process that file
with simple code to generate a stereo file, which you can
then play repeatedly with Cool Edit or similar.

If it is real time, but you have access to the source code,
add the phase shift code to the sound output routine.

If the software can only output to the sound card, and
is not open source, it should be possible to create a
virtual driver that looks like a sound card at one end,
processes the samples, and outputs stereo to the real
sound card.  This is way beyond my programming ability,
but perhaps someone on this list knows how to write drivers
for Windows, and could help with this task.

73,

Stewart KK7KA