One of the lessons learned from our group’s activities at the Oso mudslide was that sometimes it would be very, very, VERY handy to be able to get an antenna up in the air – say an additional 20 to 30 feet – to get over nearby obstacles and otherwise get a better and clearer signal – both in and out.
As a result, I now have a portable (loosely defined) pole/mast that in theory could get up to 40 feet high.
(Click for full size.)
The mast, pictured at right set up to 25′ (yes, it’s slightly crooked) needed to meet a couple of conditions: be stable, be able to be deployed by one person (me) and be relatively portable.
The pole itself, recommended by a friend and fellow ham, is actually a “Military 4ft Aluminum Pole camo netting support kit” consisting of several 4 foot sections that – if you put enough of them together – can reach over 40 ft. (They each actually add around 3’9″ to overall height when assembled, and the kit came with 12.)
On one segment I attached semi-permanantly a mobile-to-base station antenna mount. That allows me to take the antenna off of my vehicle (or any NMO mount antenna) and attach it as the antenna at the end of the pole. Regardless of the number of sections I use, and the height I select, I simply slap this section on the top. Since I don’t expect to go to 40 feet, ever, I can use another segment to perhaps put another mount on which I could someday put a true base antenna.
To that section I also attached three guy-wire cords at the bottom, meaning that the last section of the pole serves as both the antenna mount at the top and the guy stabilization point 4 feet lower.
To raise the antenna myself I first do a little math, calculating a 3/4/5 right triangle based on the distance of the guy wire connection to the base of the mast. I plant stakes at three roughly-equidistant points (the “3” length) around the base, and connect up two ropes at what should be approximately the appropriate distance (the “5” length). Since I’m using para-cord that stretches it’s definitely an approximation. Then I lift the antenna vertical and tie off the third guy wire. After that I spend perhaps most of my time adjusting the lengths of all three cords to try to bring the mast to roughly true vertical.
The biggest issue when raising a 25ft mast with antenna and cable is that as you raise it once you get past a certain point it wants to tip backwards. Since the poles are hollow I solved this by first planting a a metal tent-stake at the base and using that as the anchor point as I lift the mast vertical.
As I write this I’ve tested it briefly once, with my HT and easily reached repeaters that are known to be difficult to reach from my location on my mobile rig.
We have something similar for our portable SAR (Search And Rescue) repeater. The four foot sections are a much better idea than ours because it is damn difficult slogging through native forest with six foot poles to make up the collapsible mast. Usually we hope everything, including the operators, will be taken up by chopper.