An adequate antenna is a requirement for a successful activation. In this month’s column we’ll look at some popular options for SOTA antennas.
- Lightweight - You’ll have to carry it to the summit.
- Rapid deploy - You’ll not have time to wait for concrete to cure!
- Adequate signal - You need to reach 4+ chasers.
Down in the flatlands, you want a really good antenna and you can afford to put a lot of effort into achieving optimum signal. When you’re on a mountain, there’s a different set of trade-offs. There may be a limited weather window or darkness may be closing in and a rapid deploy can make the difference between a successful activation and a scrub.
If you set off with a 5 watt HT and a rubber duck, you’ll need chasers nearby. Most of the time, you’ll need something better.
You don’t need a 7-element Yagi-Uda atop a 30’ mast for a SOTA activation, although that is certainly an option if you have one and can carry it. A quarter-wave whip will make some contacts. It can be improved with the addition of a “tiger tail.” A tiger tail is just a 1/4 length of light, insulated wire with a ring terminal on the end. You put it over the antenna connector on your HT, screw on the antenna, and you convert your 1/4 wave antenna into a vertical dipole. I work contacts at 100+ miles with 5 watts using one of these. A roll-up slim jim is another popular option.
Line of sight is much, much better from the top of a summit than around town. A rubber duck will work just fine to reach metro Atlanta from Stone Mountain or Kennesaw Mountain. With a quarter wave vertical dipole, you can reach Atlanta from many summits in north Georgia. (Be sure to line up some local chasers in advance, and don’t forget that only simplex contacts count.)
Due to the light weight, most SOTA activators use wire antennas. You can hang your wire vertically from a tree, string your wire horizontally through branches you can reach, or use a lightweight mast. Many activators tie a string to a found rock, throw it over a branch, and hoist up a wire. I’ve got a terrible throwing arm and I like a consistent deploy process, so I carry a carbon fiber mast.
The classic dipole gets good results, and some activators swear by it. This antenna is particularly popular with activators who do not carry an antenna tuner, due to the ability to rig it for low SWR. The most common configuration is an inverted V. If you suspend the center from a mast, you’ll need to carry a mast stiff enough to support it, and that’s generally somewhat heavy. If there are trees on the summit, you can suspend the center and the ends from the trees, but setting up three support points takes longer than I generally like. If the center is up high, you’ll also need to carry a long feed line, which increases your pack weight.
An end-fed is generally the most popular antenna for most activators due to the ease with which it can be deployed. If your radio has an ATU, you can throw one end of a 35.5’ wire over a tree, attach the other end directly to your radio, string a similar length counterpoise through the bushes, and you’re on the air in minutes.
My personal favorite is to zip tie 32’ of wire to a 35’ carbon fiber fishing pole, and to lean the pole against a suitable tree branch. If it’s windy, you’ll need to guy it or to tie it off to the tree. On a treeless summit, three aluminum stakes and three lengths of string will guy it with a few minutes of effort. If you run it through a ‘matchbox’, it’s an end-fed half-wave for 20 meters. (I routinely work the UK and Spain with this.) To switch to 40 meters, run 32’ of wire through the bushes and attach it to the ground terminal on your radio and you have a dipole (or you can think of it as a single-radial vertical, if you prefer).
- Start with what you have. If you can get it to the summit, it is good enough to get started. You’ve got elevation working in your favor, and many summits are free of RFI. RF in the shack is not something you have to worry about. (There’s no shack and you’re running low power.) Keep in mind that you only need it to stay up for about an hour; this is not a 20-year antenna!
See you on the summits!
73 DE K4KPK / Kevin
Where can I find out more?
- A popular EFHW: http://www.lnrprecision.com/endfedz/trail-friendly/
- EFHW Central: http://www.aa5tb.com/efha.html
- K4KPK’s site: http://k4kpk.com/content/sota-menu
- Email me (K4KPK). My email address is available via http://www.qrz.com/db/K4KPK.
K4KPK, Kevin Kleinfelter is Georgia’s first SOTA Mountain Goat. He has completed more than 150 activations.
This story is Copyright 2015 Kevin P. Kleinfelter. A non-exclusive right to redistribute in electronic or printed form is granted to amateur radio clubs operating in the metro Atlanta area. All other rights reserved.