[A-DX] Slow Scan Radio #029 storyboard / sonogram

[Roger]

Am 09.03.2019 um 21:54 schrieb John Piek (ICT-translations):
> ....it is really amazing how good you got even the MFSK images. 
> ........there I had QRM from the SSTV on the MFSK images, but I don't 
> see anything of that in your page.
> In fact, last afternoon with me only 50 - 60% of the data was 
> undamaged, and I had some reports that were the same.
> I have sent your URL's to Hans of WINB, for the managers of the 
> station wanted to see what I was doing, and this was the easiest way 
> to let them know :)
>
>

First I had the problem - that despite perfectly decoded image preamble 
- FLDIGI did not change to the image mode.
Presumably, the set AF frequency (512 Hz) for a more than a 1kHz wide 
mode is just too low, the gap is definitely too narrow.
So I created an offset of 1 kHz at the subsequent decoding of the second 
reduced track. (that was my "trick")
Thus, the MFSK-64 track appeared at 1512 Hz, within the "expected range" 
of FLDIGI.
FLDIGI obviously has problems with MFSK64 when:
- 10% of the required bandwidth is missing
- the sounds of the digital modes are partially in the low bass range of 
the AF



> Next Saturday the show will also be on 9265 kHz at 1730-1800 UTC in AM 
> (not DMR this time). At the moment I don't know for sue whether we do 
> another test on 13755 on Friday in DRM next Friday.

SSTV via AM, yes that sounds reasonable.

An analogue or digital modes via bubbling DRM audio is just plain nonsense.
With such a miserable audio one can only test the robustness of digital 
procedures and their error protection, but do not expect grandiose pictures.


roger