by Klaas Robers » Sun Mar 25, 2018 3:47 am
This is indeed SSTV over short wave. The FM-signal is quite distorted due to the reflections in the ionosphere. However without those reflections there would have been no signal at all.
In the very beginning there were experiments done with the video signal modulating a tone in amplitude (AM), but that gave even more distortions in the received video signals. So Cop McD switched to Frequency Modulation of the tone. It is by accident that speech, transmitted in SSB, is not so much affected by the ionospheric reflections and imperfections. That is to say: it is affected, but we don't hear it, the speech is still understandable.
But it is good to see that in 1982 still the 120 line standard was used. 1982 was also the year of the emerging IBM compatible PC, so the computer modes of SSTV, in colour and with more lines, were just to come.