[amsat-bb] [Video] HuskySat-1 decoded with manual tuning and no SDR

[John Brier]

Thanks Zach.

I noticed the spinning too, and noticed it was not what others have shown
in their videos, so figured it had to do with my manual tuning, so thanks
for verifying.

I read the first page and that doc looks like a really good primer on
digital RF. Some of those diagram might as well be art.

73, John Brier KG4AKV

On Sun, Feb 2, 2020, 20:44 Zach Metzinger via AMSAT-BB <amsat-bb at amsat.org>
wrote:

> On 02/02/20 18:50, John Brier via AMSAT-BB wrote:
> > One thing I didn't mention in the video, at the end of the pass around
> > 10 degrees elevation and lower I decoded a lot of frames because the
> > signal was still strong and by that point the frequency wasn't
> > changing much anymore, as the satellite's relative speed stopped
> > changing.
>
> The video is instructive as one can see the plotted constellation
> "spinning" before symbol lock. Even after locking, the constellation
> rotates, indicating a frequency error between the transmitter and
> receiver presenting itself as a continuous phase rotation.
>
> With an antipodal signal, the constellation diagram will tell you a lot
> about received signal quality, including SNR (fuzzy points), interfering
> signals (donuts), out-of-lock (one big circle), frequency/phase errors
> (smeared clusters of points in a radial pattern).
>
> A great technical read on vector modulation analysis:
>
> http://literature.cdn.keysight.com/litweb/pdf/5091-8687E.pdf
>
> --- Zach
> N0ZGO
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