Antenna

We couldn't really come up with a good antenna to use, and buying one like I wanted to take was really cost prohibitive. I've tried to keep spending very low for this trip, so we decided to design and build an antenna ourselves. I think I mentioned that we had several ideas, including curtain hangers and similar ideas.

What we finally decided to do was a coil-loaded dipole. It had to be lightweight, short when transported, and easy to put together, and work on basically one band. If you're not dealing with multiple bands, that makes it much easier.

Wire antennas are out because we don't have a place to string them at the hotel where we're headed. Besides, we wanted to do our operating at on near the beach and not in the room. Otherwise, we'd just have asked the hotel to let us string a wire antenna.

So, what we came up with was a tuned dipole, made from aluminum arrows, PVC piping, some screws, washers, arrow inserts, an SO-239 connector and some wire for coils.

I spent the last few days reworking some cheap aluminum arrows into ordinary tubes, cutting off the nock end, removing the plastic insert that you screw the arrow head into and cutting them to the proper lengths based on calculations I did.

Last night I assembled the whole set up after finishing some short pieces of tubing for tuning, and placed the antenna assembly up on a short, 5 foot pole, on top of the trippod we'll be using, connected a 30 foot piece of coax, and fired up the rig as it will be carried, including the microphone and power supply.

It took me rougly 2.5 hours to get the antenna arms the right length and I kept showing high SWR of 1:3 or so and I couldn't seem to get it down. Finally I took the end tubing off from the coils outward, and placed a 30 inch piece in place. The SWR dropped down to 1.25:1, so I replaced that tube with a set of extension antennas from some old handheld CB radios and started slowly increasing and decreasing the length of the arms by first 1/4" then by 1/8".

After another flurry of jumping down off the deck, moving antenna robs, jumping back up on the deck, and setting the meters, checking SWR (I repeated this process at least ten times) I was down to 1.2:1 and I stopped there. I chopped a bit off of a couple of arrow-rods, and replaced the whole thing, then responded to a fella in PA calling CQ. He gave me a 5 and 4, then a 5 and 9 report. I was happy.

Here I was pushing 35 watts, on a home brew dipole practically sitting on the ground and I was getting a 5 and 4 report. Then I turned the antenna slightly and both his signal and mine went up.

A bit later, I called CQ and was answered by a Ham in New Jersey. I'm sorry I didn't write down the first call, but the second one was WW2QQ and he gave me a 5-4 then a 5-7. I think I can call that a successful antenna. The real test will come sitting on a beach in Jamaica, with a cold beer next to me, on the beach.

I'm happy. Except for one thing. The antenna isn't as "sturdy" as I'd like. I had to reinforce the center piece (PVC T-section) and the arms on either side with a fiberglass rod extending on both sides.

I'm concerned that the thread-stock I used is too small, but 8-32 screws are prettu much what fits into then end of arrow, so, I am stuck with that. They will probably hold, and I might be able to make the threaded portion a little longer to give it a bit more support, but the inserts aren't very long to begin with. I'll work something out, even if it is a string-eyelet type set up to give a little suspension to the arms of the antenna.

This weekend I'll set up the rig and operate from the back yard for a few hours each day and see what this antenna will do... or maybe we will climb Pikes Peak and set up there for a few hours!

73,

Rick Donaldson, NØNJY