[amsat-bb] Unusual ISS SSTV signal

[Loren M. Lang]

During one of the SSTV transmissions today, I heard an unusual signal
overlaid on top of the regular SSTV signal. It started just after the
original SSTV signal, and was initially quite strong, but eventually
lost out to the regular SSTV signal. It sounds similar to SSTV, but
not quite the same. This started at 2020-10-06 02:54:32Z. You can hear it here:

https://www.dropbox.com/s/abcizkoly8rn1ij/funny-sstv-signal.mp3?dl=0

You can see the waterfall during the initial decode here:

https://www.dropbox.com/s/dxmy4rhruiit84v/funny-sstv-signal.png?dl=0

It does look like a separate signal on top of the original SSTV signal
and it looks more centered on 145.800 MHz than the Doppler shifted ISS
transmission which makes me thing it might be terrestrial, but I have
no idea where it would be coming from. It definitely looks like it was
targeting 145.8 and it sounds SSTV-like. The signal poped in several
more times as can be seen in this waterfall:

https://www.dropbox.com/s/gwh4h4b1d8qtnbv/funny-sstv-signal2.png?dl=0

Any ideas what this came from?

Here's the image I received during that pass:

https://www.dropbox.com/s/j11wj6yo9s2ceg9/sstv-202010060311.png?dl=0

I do have the raw baseband signal if anyone's interested.

-Loren
K7IW