31 March 2018
Following the first 160m challenge in 2017 I had been considering various antenna options for the 2018 event. Back in 2017 I used a low doublet antenna that was really not designed for the 160m band and although I did make 3 contacts with it, its performance left much to be desired. The question was (and is) what sort of antenna is both efficient and portable enough to be used in a SOTA activation? It had to be relatively lightweight, simple to assemble and deploy, and reasonably efficient to make the most effective use of the low transmit power.
I considered a helical vertical with a capacity hat and a network of ground radials but discarded that idea as it didn’t meet at least two of my criteria. The only thing that looked promising was a kite-borne long-wire. I hadn’t used a kite before but I knew a few people who had and remembered them saying how impressive their results had been on the lower HF bands, so I decided to give it a try.
I did a bit of reading to see what I would need to make that work and found quite a lot of information on the web, some of it useful and some of it frankly hilarious (e.g. Peter/VK3YE at https://www.youtube.com/watch?v=39sA4e-hfeg) and some very helpful (e.g. David/VK3IL at http://vk3il.net/projects/experiments-with-160m-antennas/). Received wisdom seemed to indicate that a lifting kite would be the best option, known in the kite-flying business as a “parafoil” or “sled”.
A little more reading (Google is your friend!) showed me that there is a huge variety of parafoils out there. They come in all sorts of sizes up to and including really big ones that will lift a human, though why anyone would want to do that is beyond me. What I needed was one that would lift a wire antenna without any drama and that would be very stable in flight so that once it was airborne and doing its job as a skyhook I could forget about it and get on with making contacts. Eventually I settled on the LS30 from Skydog Kites, available from various suppliers including Kitesmart in Melbourne. This is a relatively small (approx 1.2 square metres) lifting kite which will fly in a range of wind conditions from 10-35 kph and is well capable of lifting the relatively light weight of a wire antenna.
Warren, VK3BYD and I had for some time been talking about doing a joint activation and this expedition looked like the perfect opportunity to do that. I knew that it would take at least two of us to get the kite and antenna airborne and securely tethered, and Warren seemed keen to join in with the experiment, so we agreed that we’d do this one together. Mt Hotham fit the bill since it’s (1) an easily accessible, 10 point Summit and (2) it has plenty of space unobstructed by trees or other objects that might become entangled with the kite line. On the day Warren brought his XYL Robyn and their family as well, so we had plenty of assistance with piloting the kite, keeping it in the air and out of trouble.
I had intended to go out for a test flight before heading to the Summit but, as is so often the case, events conspired against me and so the first time the kite came out of its bag was when we were ready to launch it on Mt Hotham. The first job was to unpack it, disentangle its rigging and work out which way round everything went. Then clip on the flying line, run it out for 30 metres or so along the ground, hold the kite up so that the wind inflates it and let it go. I could not have done all that on my own, but with faultless teamwork by Warren and family we got the kite airborne without any drama at all. Fortunately we found a nice, solid wooden post which we could use to tether the kite line to, so that we didn’t need to have someone continually holding on to it.
We found that despite its small size this kite pulls like a train and would obviously have no trouble lifting the 31 metres of wire that I was going to use for the antenna.
The next task was to bring the kite back down, attach the antenna and then launch it again. Having done my homework I knew how to get the kite down – slip a carabiner onto the kite line and walk down it, pulling the kite down as you go. This avoids getting rope burns from the kite line. The parafoil, having no frame, collapses easily when its geometry is disturbed so having got it down to the point where you can grab it, you don’t have to fight with it to finally bring it to the ground.
We were very pleased to find that with the antenna attached, the kite launched and flew just as easily as it had without it. I attached it with a swivelling spring clip acquired from a fishing tackle shop, with a short length of shock cord below that. At the ground end, the wire was tethered to a metal tent peg again via a short length of shock cord. The wire was then plugged in to a 4:1 balun, the opposite side of which was grounded to the tent peg to provide a path to earth for any static built up on the antenna. Finally, a long counterpoise wire was plugged in to the earthy side of the balun and run along the ground.
With the antenna in place the kite was reasonably stable in flight, though to begin with the wind was a bit gusty and the kite did move around a bit in the turbulence. It crashed once or twice in the lulls between gusts and had to be relaunched. Robyn discovered that if the kite appeared to be heading for a crash, a good strong tug on the line would often cause it to recover so she then became the designated pilot and kept us airborne. Later, towards sunset, the wind became a little stronger and steadier and the kite became much more stable as a result.
The Barrett 940’s auto ATU tuned the system to a good match on all the bands we tried, including 160m. We started out in chaser mode and made the first contact of the day with John VK6NU on 18MHz. A string of contacts followed on 7MHz SSB and CW including several European stations. We took a break for dinner before going onto 160m, where the results were very pleasing with a string of contacts including three Summit-to-Summit QSOs.
When the sun went down the temperature went down with it, reminding us that we were at 1800 metres altitude. When the battery ran flat we were not disappointed to call it a day at that point. Getting the kite down in the dark posed fewer challenges than I had expected and we were packed up and off the hill inside half an hour.
My thanks to Warren, Robyn and family for making this such an enjoyable SOTA outing. We all learned a lot as well as having a lot of fun. No doubt we will be back to do it again some time!
Note: this is the list of stations worked by me, VK2IB/3. Warren, VK3BYD/P also worked most of these but his list will be a little different as we didn’t always hand over the key/mic on every contact.
Stations worked on 1.8MHz CW:
VK3ARH/P (S2S VK3/VG-010), VK5IS, VK4TJ, VK3PF/P (S2S VK3/VT-049), VK3CAT, VK3IL/P, VK3APC, VK2EIK, VK2IO/P (S2S VK2/SY-002),
Stations worked on 7MHz CW:
VK2IO/P (S2S VK2/SY-002), EA2LU, ZL1BYZ, HB9DQM/P (S2S HB/ZH-014), EA2LU, ZL1TM,
Stations worked on 7MHz SSB:
VK3PF/P (S2S VK3/VT-049),
Stations worked on 18MHz SSB:
VK6NU/P (S2S VK6/SW-039),