[amsat-bb] Re: Digital Slow Scan in space

[Trevor .]

--- On Fri, 7/9/12, g0mrf at aol.com <g0mrf at aol.com> wrote:
> An essential feature would be that whenever a 'packet' of
> data is received, that data is displayed rather than waiting
> for the complete image to be received error free.
> I couldn't find much on DRM encoding but I think it was
> originally intended for digital voice in a narrow bandwidth
> so it sounds suitable for low power satellite use.

WinDRM (and DRMDV/FDMDV) were written by Cesco Lanza HB9TLK some info at 
http://n1su.com/windrm/download.html 

To achieve a reasonable data rate it's usually run at 64QAM (with full SSB bandwidth). 64 QAM is less robust and requires a higher S/N. 

I've no idea what the practical effects of a high Doppler shift would be, although a computerized station with frequent Doppler correction should track it okay. 

Is the data rate on High Altitude Balloons about 300 bps ? I've never received any images from them but if 300 bps is correct then the images are either low res or take a long time to send ?

Analog SSTV is still going strong some 6 years after the introduction of Digital SSTV perhaps indicating that existing Digital SSTV approaches do not yet match the performance/robustness/ease of use of analog for HF working.

73 Trevor M5AKA