[Lowfer] Phasing exciters

[Ed Phillips]

Stewart Nelson wrote:
> 
> 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


	I just looked at your reference for a "Hilbert Transformer" but the
Introduction and Design "are yet to be written).  The arithmetic for a
Hilbert transform is straightforward (maybe with a little help from
Bracewell) even for a dilbert like me but I have never understood the
hardware/software implementation.  

	I'm nowhere near up to modifying any of the code (the only languages I
speak are Basic and a little bit of ancient Fortran), but I certainly
can build the hardware.  For the immediate time I'm begging the issue by
firing up an old tube-type transverter which converts 80 meter signals
down to the 160-190 kHz region.  I've traced out the schematic and will
try to apply power to it over the weekend.

Ed