[amsat-bb] Unusual ISS SSTV signal

[Loren M. Lang]

I'll give you my take on it. My initial report looks like local
terrestrial interference because the waterfall seems to show a very
strong signal centered on 145.8 over the slightly doppler shifted SSTV
signal as can be seen here:

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

I would like to think it was non-malicious as that doesn't seem
likely, but it coincided very closely to the start of the next SSTV
transmission and was nearly the same bandwidth sounding SSTV-like, but
not quite. Maybe the sound was due to some mixing of the two signals,
but I don't think that would produce the sound I heard. The second
issue started when the SSTV transmissions went silent around 15:00 UTC
on 10/6 as can be seen by all the read reports here:

https://amsat.org/status/

The first block of red reports was due to the Cygnus docking on 10/5,
but it came back later that day well before they said it would resume.
It was up for several hours and went silent on 10/6 for a reason that
I don't know yet. When it came back, the pictures were distorted for
several passes I tried. This time, it looks like the signal itself and
not interference. Maybe the audio was mis-adjusted and distorting, but
I had near perfect condition and even did some post-processing and
doppler shift correction with the raw, baseband signal after the fact
and it still produced an ugly image. I could even see the ISS during
the pass and visually track it with my handheld Yagi. This was 02:00
10/7 UTC. Here's the best I could get out of that pass:

https://www.dropbox.com/s/a3ibnks6ionwwt2/bad-sstv-202010071920.jpg?dl=0

The next day (for me) at 18:30 10/7 UTC, It was much improved and I
captured this on my phone directly without any post-processing or
doppler shift correction:

https://www.dropbox.com/s/39feej142tn9gcd/20201007_133152.png?dl=0

I've captured multiple images on several passes since with similar clarity.

-Loren
K7IW

On Wed, Oct 7, 2020 at 6:26 PM Greg D via AMSAT-BB <amsat-bb at amsat.org> wrote:
>
> Good passes here, too.
>
> So, with the dust settling on this little adventure, do we know what
> happened?  What rigs were in use for what roles? Where was the
> interference coming from?
>
> Greg  KO6TH
>
>
> John Brier via AMSAT-BB wrote:
> > Any chance you had dual VFOs and one tuned to 437.800 as well as 145.800?
> >
> > On Wed, Oct 7, 2020 at 1:36 PM Vince Fiscus, KB7ADL via AMSAT-BB
> > <amsat-bb at amsat.org> wrote:
> >> At 11:57 AM 10/7/2020 -0400, you wrote:
> >>> Was it a female russian voice? They have a system that announces the
> >>> locations they are passing over and it gets into SSTV transmissions
> >>> somehow/sometimes.
> >>
> >> No,
> >> Just a number of english speaking U.S. OM's making fm contacts. The sstv
> >> was louder than they were.
> >> KB7ADL
> >>
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> _______________________________________________
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