Working Satellite SO-50

One aspect of amateur radio that I am enjoying lately is working the FM satellite SO-50. To do so I use my Boafeng GT-3TP dual band hand held and an Elk log periodic antenna that I have mounted on a camera tripod.

My basic satellite communications setup.

SO-50 carries several experiments, including a mode J FM amateur repeater experiment operating on 145.850 MHz uplink and 436.795 MHz downlink. The repeater is available to amateurs worldwide as power permits, using a 67.0 Hertz PL tone on the uplink, for on-demand activation. The repeater consists of a miniature VHF receiver with sensitivity of -124dBm, having an IF bandwidth of 15 KHz. The receive antenna is a 1/4 wave vertical mounted in the top corner of the spacecraft. The receive audio is filtered and conditioned then gated in the control electronics prior to feeding it to the 250mW UHF transmitter. The downlink antenna is a 1/4 wave mounted in the bottom corner of the spacecraft and canted at 45 degrees inward.

The Elk was loaned to me by Wal, VK4CBW, an avid satellite fan who lives down the road from me. The antenna is basically a held-held job but I do find it gets a bit heavy after a while, hence the tripod.

Today SO-50 was within range at 4.56pm, so I put out a call and was answered by Roy, VK4ZQ, from Nundah in Queensland. And although Roy isn’t that far from me, the satellite is. The apogee height is 665km, which means at its furthermost distance from the earth, it is 665km away. Not bad for a two-way FM contact.


Better antenna for satellite work

Having worked my fist ‘bird’ with a hand-held, it was time to take the next step and try using a better antenna. The ubiquitous ‘rubber duckie’ has been said by many to be nothing more than an eloborate ground; it’s certainly a compromise antenna designed for simplicity and basic functionality at best.

Wallace, VK4CBW, suggested I try working SO-50 with a gain antenna as it would improve transmission and reception markedly. He offered to lend me his Elk hand-held antenna.

This antenna is a log periodic cut for the 2m/70cm bands and is only two foot long – perfect for satellite work.

I assembled the antenna (it comes with the elements all colour-coded for easy assembly) and put out a call the next time the satellite was within range. Bob, VK3MQ, replied and we had a superb, short, QSO. I was delighted as the distance between us was 1,346 km (836 miles). Not bad for an FM contact on simplex.


Next I worked Cam, VK4FAAJ, who was using a hand-held coupled to a home-brew yagi he made from a tape measure! Nice copy too, even though he was in my neck of the woods.




Working the satellites

I always wanted to work the satellites as there seems to be something mystical about them. They aren’t called ‘the final frontier’ for nothing.

After talking to Wallace, VK4CBW, it became apparent that this would be quite feasible with a dual-band hand held transceiver and some satellite-tracking software on my computer.

My Boafeng GT-3TP would do fine so I downloaded and installed gpredict into my Surface Pro 4.

I proceeded to monitor my satellite of choice, SO-50, which I chose because it is an FM satellite. Wallace helped program in the receive and send frequencies into my hand-held; receive frequencies starting at 436.805 and progressing down at 5khz intervals to 436.780 would be needed to take the Doppler effect into account. Transmit frequency remains at 145.850.

screenshot-1   As the satellite came within range I headed outside and turned on my hand-held, with the squelch turned right down. Pointing the rubber-duckie antenna towards the ground, I put out a call .. and listened. Turning this way and that, I repeated the call until I heard Wallace reply.

I had made my first contact. The interesting thing about this was that his shack is only some 300m down the road from my shack, but we were communicating via a satellite in space. The pass only lasted around eight minutes or so; brevity is the name of the game here.

My next attempt would be with an Elk antenna, a specially-designed four-element log periodic antenna that Wallace will lend me.