08 September 2007

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!


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