My First 20 Contacts on LEO Satellites with Omnidirectional Antenna

My First 20 Contacts on LEO Satellites with Omnidirectional Antenna

At the outset, let me tell you that I do not intend to say that vertical omnidirectional antennas are the best way to make contacts through the transponders of Low Earth Orbit (LEO) amateur radio satellites. On the other hand, it is meant to motivate my friends, especially senior citizens, who shy away from attempting amateur radio contacts through satellites because they are unable to go out and work using portable radios and directional antennas tracking the azimuth and elevation of the fast moving satellites. Of course, there is also a way of operating from the convenience of the shack using circularly polarized dual band cross Yagi antennas with antenna rotators capable of tracking the satellite movements using computers. This coupled with automatic Doppler tracking radios and software would be the ultimate convenience, but quite expensive as well.

My dream of working amateur radio satellites remained a dream till a LEO Satellite Repeater Contact WhatsApp group was formed in August 2023. There was hectic activity on the group with many Elmers giving advice on how to work the LEO satellites and there was also some discussion on MEO satellite Green Cube and even on GEO satellite QO 100. We began tracking the satellite passes using websites and apps and many of us started posting passes of satellites with high elevation passes in our region. Intially we thought of tracking Doppler by programming three frequencies above and three frequencies below the nominal frequency of the uplink and downlink of the satellite. Later we were told about the Argentinian Amsat website which gives instantaneous values of Doppler for numerous satellites. This was useful while working from within the shack with a base station. N2YO website would give 10 day predictions of the satellite passes and also give a direction of the passes with timings in multiple locations.

When there is a reasonable elevation pass in our region, we would be informing others on the group to be ready with their setup. Some would go to the terrace with their hand held directional antennas and radio while those with better set up would be in their shack with trackable Yagi antennas and Doppler tracking software. Anyway, it was a group effort which helped many of us to have contacts through low earth orbit satellites, predominantly the International Space Station and Tevel series of satellites. Some were also lucky to work through AO 91 during occasional passes at day time when the solar panels would permit contacts through the otherwise poor battery status of the satellite. Timing of activation of Tevel series was available from the Twitter posts of David 4X1DG, which were also regularly monitored and posted to our group by members.

When we wanted to know whether a particular pass would overlap between two distant grids, we used the SatMatch website, which gives the periods of overlap between passes of the satellites in the coming 24 hours. This allowed members from the grids to be ready and look out for those who are likely to be audible during the given pass. AMSAT Live OSCAR Satellite Status Page was another useful resource for us to check whether the satellite which we are trying to work has been reported to be active. This avoids wastage of time looking for an inactive satellite. In turn, we would also submit our reports on the website of the satellites we hear, so that it will be useful for other operators globally.

LILAC Sat 2 is active for 24 hours at a time, starting around 2200 UTC on Mondays, Wednesdays, and Fridays. Some of the group members have been able to access LILAC Sat 2, though I have not been able to. Another satellite which is occasionally active is UVSQ-SAT, the schedule of which is posted on their Twitter page. PO-101, also known as Diwata 2, also posts the schedule for switching on the transponder on their Twitter page. None among our group have been able to access these two satellites yet.

Many of those in the group who have not been able to access the satellites, have still been able to hear the transmissions from others. They provide valuable data to others who are active on the satellites. Many of them have copied International Space Station with the inbuilt whip antenna of the handheld radio. Audio recordings provided by them have been a great encouragement initially when we could not complete a contact across the transponder of the LEO satellites.

Some of them are not able to access the satellites because of local restraints like no access to terrace and blocking structures nearby their homes. Even remote rare grids are being activated by the group members, with great enthusiasm.

In my personal experience with a CP22E VHF antenna and a dual bander base station, I found that I am able to access better if the passes are from the South to North along the Western side, with moderate elevation. My antenna is on a one length GI pipe on my first floor terrace, with 10 m of HLF 200 cable feedline. It is well grounded using 4 sq mm insulated copper wire and a copper plated iron rod about 4 feet long. Total height from the ground level would be about 9 m. There is a concrete water tank quite near the antenna on the Eastern side. I wonder whether the tank is blocking access on the Eastern side. On the other way, I have a remote feeling that it might also be reflecting my signals to the Western side, allowing better access for passes on that side! This is just a speculation. I had to choose this particular location of the antenna for safety concerns, as a bare low tension three phase electric line is passing along the road on the Western side. So I wanted maximum possible spacing from the electric line.

I did also construct multi-element Yagi antennas as per the advice of Elmers on the group. A seven element VHF and 5 element UHF Yagi are there with me. But adjustment of the Gamma match and fine tuning has been a bottle neck. The lowest SWR which I could achieve was 2.25 or 2.5:1. Of course, more work needs to be done on tuning the antennas, mounting them and getting a rotator. Even on a fixed azimuth and elevation, and a much lower height than than the CP22E antenna, I could receive International Space Station better than with the vertical antenna. But I am unable to transmit because of the elevated SWR. As I have only one good radio, even if I make the antennas ready for transmission, I will still need a diplexer, leave alone the cumbersome manual rotation procedure during the rapid pass of the LEO satellite.

Till these bottle necks can be over come, I will have to be satisfied with the limited number of contacts on LEO satellites. My current strategy is to listen for calls from others and answer only if I can hear them clearly.