Remote control of the W2MMD Satellite Station
This is really cool... Thanks to the contributions of K2QA and K2ZA we have the beginning of remote access to the W2MMD satellite station. There's a lot more to do, and use of the station requires the user to have almost all of the required software installed on their local computer, but for the true satellite experimenters this isn't a problem. This setup essentially lets the user use the antennas and radio at the W2MMD site, but everything else runs locally at their home QTH. For hams like me (WB2MNF) who are in HRO-restricted locations it's the best of both worlds.
Here's the overall concept - the remote user connects via VPN to the GCARC clubhouse network. The satellite computer needs to be running (can't remotely turn it on - yet). The SDR Console program has a server component that must be running, and the user connects to that server from a local copy of SDR console and selects one of the radios attached to the W2MMD satellite computer (currently there's only one FunCube Dongle there). Once connected to that SDR radio the remote user's copy of SDR console is now using the radio and antennas at the W2MMD site, but controlling the radio freq, mode and everything else from the remote copy at the user's QTH. Importantly, this means that the radio audio is on the remote computer, which means that the user can pipe the audio into modem, SSTV, fax and other software at his local site.
That's half of the issue. The other half is how to point the antennas at W2MMD to the satellite that you want to work. Fortunately the PST Rotator software has a client/server component that will let the remote user run the client version at the remote QTH and command the antennas at W2MMD. This lets the remote user run PST Rotator locally to control the Doppler shift on the local SDR radio (which is using the IQ feed from the W2MMD SDR server) and also to control the rotators at the W2MMD site.
With this setup users can receive any of the satellites using their local satellite computers connecting to the W2MMD antennas and needing no local antennas. Pretty cool, eh?
There are a few issues still to work out. The astute reader is already asking "OK, but how about transmitting?". That's working too, but not entirely smoothly and it hasn't really been tested thoroughly. See the Remote Audio blog for info on that implementation. Another solution is for the user to use a local transmitter if he has one - I'm planning to try using my FT-991a with my attic-mounted eggbeater antennas and see if additional power will substitute for lack of gain.
Also - what about multiple users? Well, that will work if all of the users want to work the same satellite. There are two caveats - first, each user ties up a SDR receiver at W2MMD, of which there's only one now. That can be remedied by adding additional SDR radios if demand gets higher.
Also - the PST Rotator server will respond to each rotation command. If 2 users are working 2 different satellites, the rotor will be moving back and forth based on which command was received more recently. This obviously won't work. If multiple users want to work the same spacecraft (copying the SSTV telemetry from the ISS, for example) that would work, but working multiple satellites simultaneously won't work. However, overlapping satellite passes aren't frequent and working out a schedule should be possible if this issue becomes problematic.
Finally - the antenna switches are manual, so how does the remote user switch antennas? We're still working on that - an automatic antenna switcher is under development, but it uses the transmit freq to set the antennas, and we don't have a solution for setting the remote freq yet. At the moment the antennas are selected at the W2MMD station site with no option for change by the remote user. Figuring that out will be a high priority.
Here's the overall concept - the remote user connects via VPN to the GCARC clubhouse network. The satellite computer needs to be running (can't remotely turn it on - yet). The SDR Console program has a server component that must be running, and the user connects to that server from a local copy of SDR console and selects one of the radios attached to the W2MMD satellite computer (currently there's only one FunCube Dongle there). Once connected to that SDR radio the remote user's copy of SDR console is now using the radio and antennas at the W2MMD site, but controlling the radio freq, mode and everything else from the remote copy at the user's QTH. Importantly, this means that the radio audio is on the remote computer, which means that the user can pipe the audio into modem, SSTV, fax and other software at his local site.
That's half of the issue. The other half is how to point the antennas at W2MMD to the satellite that you want to work. Fortunately the PST Rotator software has a client/server component that will let the remote user run the client version at the remote QTH and command the antennas at W2MMD. This lets the remote user run PST Rotator locally to control the Doppler shift on the local SDR radio (which is using the IQ feed from the W2MMD SDR server) and also to control the rotators at the W2MMD site.
With this setup users can receive any of the satellites using their local satellite computers connecting to the W2MMD antennas and needing no local antennas. Pretty cool, eh?
There are a few issues still to work out. The astute reader is already asking "OK, but how about transmitting?". That's working too, but not entirely smoothly and it hasn't really been tested thoroughly. See the Remote Audio blog for info on that implementation. Another solution is for the user to use a local transmitter if he has one - I'm planning to try using my FT-991a with my attic-mounted eggbeater antennas and see if additional power will substitute for lack of gain.
Also - what about multiple users? Well, that will work if all of the users want to work the same satellite. There are two caveats - first, each user ties up a SDR receiver at W2MMD, of which there's only one now. That can be remedied by adding additional SDR radios if demand gets higher.
Also - the PST Rotator server will respond to each rotation command. If 2 users are working 2 different satellites, the rotor will be moving back and forth based on which command was received more recently. This obviously won't work. If multiple users want to work the same spacecraft (copying the SSTV telemetry from the ISS, for example) that would work, but working multiple satellites simultaneously won't work. However, overlapping satellite passes aren't frequent and working out a schedule should be possible if this issue becomes problematic.
Finally - the antenna switches are manual, so how does the remote user switch antennas? We're still working on that - an automatic antenna switcher is under development, but it uses the transmit freq to set the antennas, and we don't have a solution for setting the remote freq yet. At the moment the antennas are selected at the W2MMD station site with no option for change by the remote user. Figuring that out will be a high priority.
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