[Lowfer] Phasing exciters

[WE0H]

The smoke test hey Ed???

Mike>WE0H


-----Original Message-----
From: lowfer-admin@mailman.qth.net [mailto:lowfer-admin@mailman.qth.net]
On Behalf Of Ed Phillips
Sent: Friday, November 14, 2003 6:13 PM
To: lowfer@mailman.qth.net
Subject: Re: [Lowfer] Phasing exciters

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
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