Rig and Antenna

Well, finally downloaded the pictures out of my camera. Here's a copy of one of the images, showing the antenna in the background.

In the left foreground is a Shure 444D, which I probably will NOT be taking now, since it weighs in at a couple pounds, and the hand microphone is much lighter. The SWR meter won't likely be going either.

The rig is actually the one that will be traveling with us. In the background, you can see the antenna set up in the yard about 40 feet away. It's 10 feet tall, roughly, and about 14 feet across.

It tested very well, and I was able to tune it down to 1.1:1 SWR at the frequencies I wanted to use. I'll add a few more pictures below, giving some details of the construction of the antenna.

The next image is just of the antenna set up on Saturday, Labor Day weekend. You can see most of the antenna, tripod and a couple of wire dipoles in the background behind the portable dipole itself. The coils are clearly visible here along with the center supporting T-section. Click on any of the pictures for a larger image.


Each of the two pieces of PVC piping are roughly 4.5 feet in length, and they are cut into two pieces each. One of the bottom sections has a pvc coupling glued to it, as does one of the upper sections. The top section, of the bottom half has a set of screw-in adapters, allowing me to shove the smaller pvc piping into the coupling at the mid point. This allows for a heavier (1.25" dia.) lower section, and a lighter piece at the top. I could cut other pieces of piping to extend the height of I wised. I have no intention of taking more weight than I have to though!

Above you can see the details of the center tee-section. An SO-239 connector is mounted physically onto the center of the Tee. On each end of the Tee are bolts, attached internally with wiring that is soldered or screwed down to the SO-239. The end caps are glued on permanently. There are bolts centered on the end caps, which are held with lock washers, flat washers and a set of internal, and external hex nuts. The bolts are actually threaded-stock that is #8, 32 threads per inch. (I think.. I'm writing this from memory, but the thread size is the same thread size that fits an arrow head onto an aluminum shaft.)

The black stripe on either side is electricians tape, and if you look carefully, over the top of the Tee, you will see a couple of fiberglass rods that are connected together, and taped over the Tee, then again taped to the antenna rods (arrows) at either end to give some support to the threaded stock going through the arrows and the Tee-section.

Above you see another view of the center Tee-section, the connector and how I used electrical tape to hold the fiberglass rods to the antenna sections.



Details of the coils. This coil is made from 1.25" OD PVC, with end caps, there are 31 turns of #14 AWG stranded wire wrapped tightly around the aircore. End caps are NOT glued, but taped heavily with electrical tape (in case I needed to later modify things, or I had issues with connectors coming undone). On the ends are pieces of threaded stock matching the arrow inserts I used, held internally with lock and flat washers, and hex nuts, and on the outside as well. The coil wiring is attached internally with small spade lugs, and tightened down very tightly. Externally, arrow shafts are screwed to the end of the coils.

At some point later, I'll do a separate article on details of how to build the coils, the arrows and the antenna parts, then assemble it, but probably not until I get back.


On the left is the actual power supply we're using for the radio. It's going to make a NICE addition to my ham shack (even though JoAnne thinks she's getting it.... :)) It's an alinco, weighs in at about 5 pounds and can handle 32 AMPS! Woot, I can run a couple of rigs at once off that.

Well, that's about it for the day. Enjoy the pictures. Please, if you're reading this, make a comment so I will know and take the survey on the bottom of the page.

Thanks and 73!

Rick, NØNJY

More Antenna testing

On Thursday of last week, I pretty much finished manufacturing the parts I needed to assemble the antenna we're planning on taking with us. Thursday evening, I fired up the rig for the first time on Thursday evening and made a half dozen more contacts with it, then Friday even we did more.

Over Saturday, Sunday and Labor Day Monday, I had the rig set up in the back yard on the deck, with the power supply we were planning on using, as well as various microphones. There were no really noticeable differences on audio quality (except when I actually placed the desk mike I was using, a Shure 444D back into High Impedance mode... not sure how I switched that off) and got "Audio is 100% better with that setting".

The normal hand mic seems good enough, and of course it is very light, so it's going. A brass key will go along, but likely will not get used.

I made a couple of dozen contacts from Canada, to Florida, to Bogotá, Columbia and several other places, including Maine, Massachusetts, Texas, and a few other places I can't recall at the moment. Signal reports varied from 5/4 to 5/9 and at least two that were 5/9 +20 db. I am very happy with the testing of the antenna.

The really cool part about the weekend (ok, WARM part!), it was very warm and I had to use an umbrella every day to keep the sun off, and of course, drink a few cold beers to "get me in the mood". We also snapped a few pictures which I will insert in the next few days of the antenna, power supply and the rig. I think I got at least one of JoAnne doing some reading at the rig. Might put that up if she "approves". :)

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

As of last Friday, we hadn't really picked an antenna yet, but have looked at several things, including a purchase of a W3FF Buddipole -- at a cost of almost $400.00. While it appears to be a very cool antenna system, extremely portable and used by several DXpeditions, we decided that was a bit out of our price range. Besides, having been a communications guy for a long, long time, and setting up almost anything in a pinch as an antenna, mostly wires, zip cord and military equipment, it was decided we build one and use as much stuff from home as possible and keep the price down. This of course, didn't preclude us from purchasing a few items at a hardware store this past weekend.

After a bit of brain storming over a couple of beers at our favorite food place, and quite a bit of drawing on napkins, we came up with a design, some calculations and then tried to come up with some kind of simple hardware we could make into an effective antenna.


We decided the following:

1) Multiband homebrew dipole.

2) It had to be light, shortened and we needed to be able to stand it in a free-standing mode with a tripod or some sort.

3) Wire dipoles were out because of the previous site surveys showing little or no antenna supports available (trees!) and we wanted something sturdy enough to stand on its own with little sag.

4) The antenna had to be fairly easy to assemble.

5) It had to be reusable, and it has to actually LOOK good as well.

We tried some extendable/expendable curtain rods and some fiberglass tent poles that are held together with an elastic string through the middle. Both sagged considerably, and were weaker than we expected. The curtain rod idea was good, but we weren’t going to use the rods as radiating elements, and couldn’t come up with a good way to put coils in place. We tried inserting wooden doweling into the curtain rods, then started thinking about the interaction of the metal with the actual antenna. That wasn't going to work well.

The fiberglass poles were just a bit heavier than we wanted, and again, with not a good way to mount things. They sagged as well, more than I thought was usable. Putting a coil and some wire along the fiberglass shafts would have worked fine, and simple electrical tape to hold it would have worked well, but the antenna would have been 16 or 18 feet long, even with the loading coils and it would have sagged miserably.

Then the idea struck us to use aluminum arrows. JoAnne had already mentioned arrows once, but as is typical for me, I was thinking one thing and she was thinking something else. I was looking at SUPPORT (and thinking wooden) and she was actually thinking of the technical aspects of using ARROWS (and thinking METAL -- Duh on me!).

So, on Sunday (yesterday), we purchased a handful of $3/ea shafts, removed the plastic arrow head inserts, and cut off the fletching and nock end of the shaft. This left us with a set of hollow aluminum tubes. Next we inserted metal inserts.

At this point, I only finished a few of the shafts yesterday afternoon, and we went off to a birthday party for one of our grandchildren. (Side note: We gave her some walkie-talkies, with a Morse code button.... so we're starting her EARLY, she's four and already knows her alphabet, so we figure by next year she will be getting her Technician license!)

Today, using a program found at K7MEM’s site, I calculated a slightly shortened, loaded dipole antenna. http://www.k7mem.150m.com/Electronic_Notebook/antennas/shortant.html

The actual “design” of the antenna will be similar to the W3FF Buddipole, including a tripod to hold the antenna up.

The center feed will consist of a T-section of PVC pipe, an SO-235 connector, loading coils for 20 meters and coils made from PVC pipe, end caps and associated hardware, screws and threaded arrow shafts. As of 27 August, the antenna is partially built and we expect to do some hard testing on 1 September 2007 to see how the antenna works.

My thinking is that we will use PVC piping as the mast section, cut into shorter pieces for transport in our suitcases on the trip. We'll use some PVC couplings to connect the pieces into a longer piece. The tripod we're going to use isn't the most sturdy thing in the world, but it was an old camera tripod and should hold this antenna up with no problem.

To build the coils I will be using short pieces of PVC pipe with end caps on each side, drill holes for the wire, and run the wires to hardware inside the pipe, allowing me to screw the newly made "Arrow Elements" to either end (on the end caps) of the coil for center loading on the antenna. I'll install an SO-239 connector on the T-section, to allow easy connection of the coaxial cable and probably install, if necessary some kind of ferrite beads at the connector to prevent RF from radiating from the coax.

Having tested some of the arrows by screwing them together already, I found that this is a very STURDY antenna element and shouldn't sag very much at all. Calculations are as follows:

Total length of dipole: 16 Feet long
Element Length Before coil: 4 feet each side
Secondary Element (Coil Plus element): 4 Feet each side

Coil specs:
Inductance: 8.76 uH
Diameter: 3 - 1/4"
Length: 1 - 5/8"
Turns: 10
Wire: #12

More to follow on this antenna. When I get it assembled, I'll try to post some pictures of it all set up so you can see what it looks like. We should be able to tune the antenna more carefully once it is put together, by adding or subtracting some length off the ends of the elements.

I think I'm going to call it a "DX-Stalker" because the arrows I'm using are made by Easton, and are called "Stalker" arrows. They are camouflaged. Perhaps we'll call it "DX-Prey" since, we'll be the DX station!