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dernasherbrezon / r2cloud

Decode satellite signals on Raspberry PI or any other 64-bit CPU.
Apache License 2.0
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Observations overlaping with two SDR's #122

Closed ArgoNavi closed 2 years ago

ArgoNavi commented 2 years ago

My ground station consists of a rotator with two antennas (UHF+VHF) connected to separate SDR's, everything is working great except the station will occasionally schedule two overlapping observations on the separate receivers and then attempt to record both at the same time.

dernasherbrezon commented 2 years ago

This is actually expected. Each rtl-sdr device is independent. r2cloud creates 2 separate schedules and load balance satellite observations between them. Most probably some observations can be scheduled in parallel.

Hmmm. Can you give more details about your hardware/software setup? What were your expectations?

ArgoNavi commented 2 years ago

My setup is a satnogs rotator with two cross yagi antennas connected to their own set of amplifiers, filters, and sdr's which are then plugged into a raspberry pi 3B+ with the rotator configured for both. Originally I planned to use a diplexer with one sdr but found it gave me very poor results and cost more than a second sdr.

My expectation was that r2cloud would work the same as with just one sdr connected choosing only one observation if they overlapped completely, if the overlap was small schedule both but either end one early to start the next if it has a higher priority or if the first satellite has a higher priority start the next observation later.

Screen Shot 2022-06-13 at 3 37 24 AM
ArgoNavi commented 2 years ago

Just realized that r2cloud with one sdr connected doesn't end an observation early or start one later when the overlap is small, it simply chooses the higher priority satellite of the two and ignores the other.

This approach would also work fine for my two sdr setup.

dernasherbrezon commented 2 years ago

I see. Essentially you want to re-use rotator for 2 different feeds.

I fear this setup is not supported yet. In this case I have to introduce some kind of logical pair of physical devices. Or create exclusive sdr devices. In that case satellites from 2 physical devices will be scheduled without overlap.

I guess the rotator with 2 different feeds is quite common. Right?

ArgoNavi commented 2 years ago

Yes that's exactly what I want, hopefully its possible to implement and not too difficult for you.

Most people with a rotator have 2 different feeds if not more. However they use a single sdr with a complicated setup involving coax switches and scrips to select the proper antenna before an observation.

https://wiki.satnogs.org/Antenna_switching

I couldn't figure out how to do this which is why I switched from using satnogs to r2cloud since it supports using multiple sdrs which is easier for me to understand.

dernasherbrezon commented 2 years ago

I implemented this feature using a shared schedule. I.e. if any 2 or more devices have the same rotator configuration (host + port), then they will share the same schedule. https://github.com/dernasherbrezon/r2cloud/blob/master/src/test/java/ru/r2cloud/it/SharedRotatorTest.java