What are all all the computer controlled stations using for doppler adjust interval? I had previously tried 100ms, and was getting about 45 frames per decent pass. I just had a 50deg pass and increased the interval to 500ms, and got almost 70 frames. I wonder if there is a sweet spot?
--Roy K3RLD
Hi Roy!
I use Orbitron on Windows and the best I can do there is one refresh per second.
I've not tried FoxTelem w/ HuskySat-1 on linux, but the nice thing about GPredict is that you can get smoother doppler adjustments by using a shorter update interval. I use 1/2 second for doppler tracking w/ GPredict most of the time.
I guess use what is producing the best result for you, but I've never noticed that the update interval was a critical factor with various telemetry decoding efforts. Much more impactful with HuskySat-1's BPSK signal is to keep that audio output centered around the 1500 Hz mark. Fine-tuning your signal during a pass to keep it as close to center as possible in your 3k passband will produce best results, I think.
-Scott, K4KDR
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On Wed, Feb 5, 2020 at 6:48 PM Roy Dean via AMSAT-BB [email protected] wrote:
What are all all the computer controlled stations using for doppler adjust interval? I had previously tried 100ms, and was getting about 45 frames per decent pass. I just had a 50deg pass and increased the interval to 500ms, and got almost 70 frames. I wonder if there is a sweet spot?
--Roy K3RLD
Ah, Great Question!
With SatPC32, the decision is based on the frequency change. In my case I have it set to 30 Hz, so once there is an accumulated Doppler shift of 30 Hz or more it will update the radio.
I've watched larger step sizes, of several hundred hertz, seem to cause the decoder (DP/Dot Product in my case) to get out of sync and miss several packets regaining sync. Smaller step sizes seem not to disturb it as much.
But I suspect there is a tradeoff, and it would be wonderful to know what an optimal step would be for BPSK demodulation.
73, Bob, WB4SON
On Wed, Feb 5, 2020 at 9:42 PM Scott via AMSAT-BB [email protected] wrote:
Hi Roy!
I use Orbitron on Windows and the best I can do there is one refresh per second.
I've not tried FoxTelem w/ HuskySat-1 on linux, but the nice thing about GPredict is that you can get smoother doppler adjustments by using a shorter update interval. I use 1/2 second for doppler tracking w/ GPredict most of the time.
I guess use what is producing the best result for you, but I've never noticed that the update interval was a critical factor with various telemetry decoding efforts. Much more impactful with HuskySat-1's BPSK signal is to keep that audio output centered around the 1500 Hz mark. Fine-tuning your signal during a pass to keep it as close to center as possible in your 3k passband will produce best results, I think.
-Scott, K4KDR
=========================
On Wed, Feb 5, 2020 at 6:48 PM Roy Dean via AMSAT-BB [email protected] wrote:
What are all all the computer controlled stations using for doppler adjust interval? I had previously tried 100ms, and was getting about 45 frames per decent pass. I just had a 50deg pass and increased the interval to 500ms, and got almost 70 frames. I wonder if there is a
sweet
spot?
--Roy K3RLD
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Scott