Amateur radio is an expansive hobby with all kinds of niches hidden throughout it. One of the ones I’ve been drawn to since I was licensed but never worked up the nerve to try is satellite communications. There are about 22 active amateur radio satellite (AmSat) repeaters orbiting the Earth, available for use. All one needs to do is find a 25cm cube over 600km away that’s speeding around the planet at 27,000 km/hr in hopes of talking to someone else able to do the same thing. It sounds a bit daunting, but that was always part of the draw.

If you’re more interested in how to reach satellite than my experience of figuring it out, I’ve put my advice at the top for ease of access.

Advice

Before the pass

  • Start with FM birds, especially SO-50.
  • Focus on listening before worrying about transmitting.
  • Double-check the downlink frequency.
  • Mark out where the antenna will be and the direction of the start, middle, and end of the pass.
  • Consider using a satellite tracking app or mark the times of the locations above.
  • Check the uplink frequency.
  • Check your satellite’s transmitting tone (SO-50’s is 67 kHz).
  • Check the range of your satellite’s doppler shift (SO-50’s is +/- 10 kHz).
  • Know your maidenhead gridsquare or write it down.

During the pass

  • Start on the high end of your satellite’s doppler shift.
  • Set your squelch to 0 or hold the monitor button.
  • Focus more on polarization than direction. Slowly twist the antenna as even ten degrees can matter a lot. Narrow in when you hear traces of voices.
  • Remember to change the downlink frequency throughout the pass. Be in the middle of the range at peak elevation.

After the pass

  • If you didn’t hear anything, check the frequencies.
  • Listen to your recording to write out callsigns or listen for moments when you thought you heard something.

Satellite Communications

I’ve had a directional antenna for this purpose for years, but never learned how to find them. When I started my college radio club, I thought it would be a good activity for us to try. After some basic research of what satellites would be in the sky and when, we went out hunting for them. We tried five different passes, but the closest we came to success was some different sounding static for a single second.

This June, I went to the Youth on the Air camp in Huntsville, AL, with the intention of building different radio skills I could pass on to my club. At the camp, I participated in satellite communications where I was not only able to hear people talking on the satellite, but also make a dozen contacts through it.

With this success behind me, I figured I should be able to do it solo. Well . . . not completely solo. For one of the satellite passes at camp, we had four people working. One to aim the antenna, one to tune the uplink and downlink, one to talk, and one to log callsigns. This was for a linear satellite, which uses HF and has doppler shift on the up and downlink. I was recommended to start with the FM birds that require simpler handhelds and you don’t have to mess with the uplink. Four jobs were still more than my two hands allowed. I considered building something to help me with one or more of the functions, but I wasn’t sure what the best setup would be as I had only done this a few times before. As I needed experience to design something*, I recruited another set of hands to help me practice.

My practice began on Field Day, a horrible day for trying to make a contact on an AmSat, but a good day to listen for one. I wanted everything to be in favor of finding one and I figured the higher up and further away from obstacles we were, the better. So we found a spot in a park overlooking the San Francisco Bay and so began the first attempt.

Attempts

Attempt I SO-50

I was too confident and so left my antenna pointer at home. We used a compass, protractor, and pass information from AmSat.org to map its path. After the first minute of the pass, it felt like guesswork as to where it was. We had two other known points, the peak and loss of signal (LOS), but were not able to find it at these locations and times.

I did find an interesting effect of listening for voices in static for too long. You start to think you hear traces of voices that aren’t there. You want there to be something so you create one. It reminds me of the ideomotor effect with ouija boards, so we started calling these instances “ghosts”.

Attempt II ISS

This attempt was directly after the first, so we had the same equipment. It was unclear how fast the satellite moved across the sky, so it was again guesswork after the first minutes. At the reset points of peak elevation and LOS, we heard “ghosts”. At the very end of the pass, both of us heard the same one, suggesting we may have been close to the satellite the whole time.

Attempt III SO-50

I thought the first two passes would be more successful, but it became clear I was not going to make a contact as quickly as I thought. I removed the 2 meter elements from my antenna as my goal changed to simply hearing one. I invested in a satellite tracking app and pointed straight at it the whole time. We heard nothing, not even “ghosts”, but a post-mortem showed we were listening to the uplink frequency instead of downlink. This gave us confidence the ghost voices from before might have been real.

Attempt IV SO-50

I had been told SO-50 was the easiest AmSat to reach, so I decided to narrow in on it. This pass introduced the side sweep instead of completely trusting the tracking app. Ghosts were heard at the very end, this time enough to make out part of a callsign.

Attempt V SO-50

This pass focused on polarization and a much slower twisting motion than I had been doing. Clear voices were heard at the right angle, but became ghosts at ten degrees and were lost by fifteen. We lost it quickly, but were able to find it two more times before the end of the pass now that I knew how sensitive the polarization was.

Attempt VI SO-50

We kept everything the same as with Attempt V, but added the 2m elements back to adjust to the heavier antenna. We lost it several times during the pass, but were able to find it quicker than the previous attempt.

Attempt VII SO-50

We added the uplink radio to our setup, but did not try to transmit. I put more focus into twisting the satellite to fine tune it while still being able to hear the voices. We only lost it once. We implemented a recorder so we did not have to write down callsigns.

Attempt VIII SO-50

This was a last minute attempt done outside my house. We found the satellite quickly and were on it the whole time. The location did not seem to matter too much, so we conducted all future passes in the same location.

Attempt IX SO-50

We attempted uplink, but were not heard. I was transmitting while holding the antenna which led to it drifting away from the satellite. I learned the downlink signal was not affected by grasping the antenna in the middle instead of the handle, which was significantly easier to do.

Attempt X SO-50

We heard my voice come back on the downlink, but the battery in my transmitter died during the contact. Holding the antenna in the middle and resting the handle against my body ensured I did not lose the satellite while transmitting.

Attempt XI SO-50

I was able to make two contacts without losing the satellite.

Attempt XII through XVI SO-50

Once I was able to make contacts, I was hooked. I made several contacts over the next few passes and was able to find the satellite faster, within two minutes of it first clearing the horizon. I also had my first encounter with bystanders wondering what I could possibly be doing. Another reason it helps to have two people is one can field questions while I’m in the middle of making a contact.

Attempt XVII ISS

The ISS has a much shorter pass I was not prepared enough for. I managed to find and listen to it, but was unable to transmit until it was too low for me to be able to make a full contact.

Attempt XVIII ISS

I was able to find the satellite quickly and began transmitting. I did not come back through the downlink. After talking with more experienced AmSat operators, I was told the ISS has a higher squelch and I would need more power. I did a post-mortem and saw my transmitter was only set to 1 watt.

Attempt XIX ISS

This was a bizarre pass. I could not find the satellite. I used AmSat.org’s pass prediction tool and had a satellite tracking app open when I couldn’t find it. I went through the whole pass hearing nothing. When my antenna was pointing at 15 degrees, I decided to end the attempt as there were houses in the way. Right after we stopped the recorder, we heard the satellite. I had it pointed at the horizon and continued to hear the AmSat for another few minutes, after the pass should have ended. I believe it is because the keplerian elements need to be updated, but it should be automatically updated in the app I have. I never figured this one out, but it never happened again.

Attempt XX ISS

I managed to find it within the first few minutes and had my transmitter set to 5 watts. I still could not get through.

Next Steps

The next step would be getting a more powerful UHF/VHF radio. I have one I use as a base station, but I would need to get a portable power source for it or find a very long extension cable. Though I still need to figure out those logistics, I feel I can say I now do satellite communications. I’ve made several contacts and can find AmSats easily and pretty reliably. I suppose my success rate is only 75% when including the attempts where I didn’t know what I was doing, but I believe in amateur radio you need a 74% to pass, so I’m good.

This was a fun niche to explore. I met some great people, my voice was heard in space, I used my radio outside in some interesting locations, and I triumphed over a challenge I had thought about for years. FM birds have been triumphed over. Once I find out how to duplicate my hands, it’s on to linears.