Yan wrote:
Hello,

I am looking to decode an SSB signals coming out of my SW
radio fed to my PC soundcard
.
There are many software available on the net but havent
been able to find on like this (BOF or some sideband
filter...)

I have seen stuff like DSPfilter and MIXsomething but
doesnt seem to do the trick.

I someone could help please.

Thanks

yan

I don't think you can take the audio output from an envelope detector of a
SSB suppressed carrier signal and convert it to the audio that you would
have got were the carrier not suppressed. The envelope detector generates
the difference frequencies between the predominant energy in the IF spectrum
and the weaker. When carrier is present, that would be the differences
between the carrier and the sideband energy, i.e., the desired modulation.
In the absence of carrier, it is a mish-mash between the strongest speech
spectrum and the weaker and no subsequent processing is liable to be very
capable of untangling it. That's why a BFO to provide a replacement carrier
and a product detector are used for SSB demodualtion.

What can be done is to downconvert the IF signal to another IF in the
passband of the sound card and the DSP processing could multiply the input
spectrum against a frequency, say 15 kHz, and low pass filter the output to
extract the modulation. Such a technique is described and Windows software
can be downloaded at http://www.detomasi.it/en/project.html. Here's a link
to an article about a DSP AM/FM/SSB demodulator based on the Motorola 56002:
http://thierry.leconte.chez.tiscali.fr/demod.html .

If you make this IF converter, you will also be able to experiment with DRM
reception using the DReaM software.

Tom