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

[Zach Metzinger]

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