Archive for the ‘Antenna Ideas’ Category

Capacitance Hat Pedestrian Mobile Antenna

Friday, September 21st, 2007

This idea stemmed from the coming HFPack gathering at Hamvention this year. Their calling frequency is 18.157.5usb. I have never really done any /PM operating before so I figured I would give it a shot. The radio I am probably going to use is my IC-718. I know, it isn’t a very compact radio, but it is fairly light and will get me on the air.

Another note before I describe the idea is all of this occurred in the course of about 6 hours – from the initial idea stimulation to the construction and getting on the air (tuned up, no contacts though).

My first idea for the antenna was a whip/mast that is 6′ tall with a cap hat on top. The mast was to consist of a PVC pipe supporting a wire. The cap hat would be made out of tape measure pieces secured to a PVC cross connector.

Once I started getting materials together I realized I had some aluminum pipe that I could use for the mast instead. It is the center section and one outer section of the separation boom for two Cushcraft 13B2 antennas. I bought 1 antenna and this boom used from a guy. The pipes
have come in handy for all kinds of things! Anyway, the pipe works very well for this project because the two sections telescope. That means I can adjust the height of the antenna to tune it.

So, now my idea has taken a new form – from the original PVC pipe mast with the cap hat to a telescoping aluminum pipe with a cap hat. The cap hat is still made out of tape measures, 30″ of 1″ wide tape for each spoke.

One big question I should address with this antenna is how it actually mounts to the pack. Well, my back pack has a pocket right against my back that is supposed to be for a water bladder. So it has a zipper right on the top of the pack. It is on the pack side of the back plate/frame. So, I made an H-frame out of PVC. It uses a T connector on the bottom with two equal pieces of pipe
pushing out





Edit: 8/24/07

Its been a long time since I posted anything new here. I figured I would update this first.

The antenna works. I ended up using my TS-2000 at Hamvention /PM. Yep, it was heavy. The rig and my lawnmower battery for power were just under 50lbs. With my pack and all loaded for Hamvention I was toting around 60lbs. Not fun.

The H-frame was poking my tailbone the whole time, so I got a nice rash there. However, that was due to the battery pushing against the H-frame. This setup probably wont be too bad with a lighter rig/battery (such as the FT-857D and a 12 or 18AH AGM/SLA battery.