[Video] HuskySat-1 decoded with manual tuning and no SDR
After some difficulty, I was able to decode HuskySat-1 on my second attempt.
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.
Thank you again to University of Washington for launching this satellite and putting the AMSAT linear transponder on it! I wish you luck in all your missions!
Check out the UW video about their satellite: https://youtu.be/U57sES6oFgw
73, John Brier KG4AKV
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
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@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 _______________________________________________ Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
Nice video. Thanks for posting. As Zach said, the spinning phasor tells us that the frequency is not locked, but that is OK as long as it is a line. The "Dot Product" decoder is not a coherent decoder so it is not in phase lock with the original carrier. The phasor is allowed to rotate and we will still get 100% decode. It can't be a circle or a cloud though :).
If you use the Costas loop decoder then it will freeze the phasor horizontally when locked because it is a coherent decoder. The two decoders have pros and cons with their ability to decode. Enjoy exploring that.
73 Chris
On Sun, Feb 2, 2020 at 9:10 PM John Brier via AMSAT-BB amsat-bb@amsat.org wrote:
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@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 _______________________________________________ Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership.
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Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
participants (3)
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Chris Thompson -
John Brier -
Zach Metzinger