After listening to the wave file, I would tend to believe that what you described (swapping "subbands" around) is exactly what they are doing. I definitely couldn't find any way to make any sense out of it with any of the PowerSDR demodulators.
Eric Wachsmann FlexRadio Systems > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] > radio.biz] On Behalf Of Jim, W4ATK > Sent: Tuesday, December 19, 2006 8:30 PM > To: Flex-radio Reflector > Subject: Re: [Flexradio] SSB Voice inversion > > > Just tuned 3700 - 3750 and heard nothing strange. > Inverted speech is a rather primitive method of speech privacy. You > can > beat the signal with a signal generator and recover the speech quite > easily. > A more sophisticated method, yet also antiquated to a degree, is > splitting > the audio spectrum into "subbands" and then shifting these subbands > arround. > Quite often they would change dynamically on a sync pulse perhaps on > another > signal altogether. Again these methods date to the WWII era or slightly > thereafter. If you have a copy of Spectrogram on your PC, you can examine > this type of privacy and get some idea of the signals spectral components. > Amazing in this digital age that there still might be some utilizing > this > rater primitive, by todays standsards, technology. > > 73 Jim, W4ATK > > > _______________________________________________ > FlexRadio mailing list > FlexRadio@flex-radio.biz > http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz > Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ > FlexRadio Homepage: http://www.flex-radio.com _______________________________________________ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
