A Hentenna calculator.

I found a description of this antenna many years ago, a couple of days before our annual field day. So  one for 6m was made, using the dimensions shown in the picture below.

The antenna was made of 1.5 mm diameter enammelled copper wire, and the upper and lower horizontal elements was routed through two lengths of plastic tubing, of the kind electricians use for feeding power cables through a wall. A third tube was used for the feed section, with the antenna element routed through two small holes in each end of the tube. This arrangement made the antenna very stable also when the wind increased.

The upper tube hanging from the top of a 6m long fishing rod, and the lowest tube was guyed to the ground to avoid twisting. The feed section was taped to the outside of the middle tube section, and fed with RG-58 coaxial cable at the center.

They say that the phrase "Hen" means "strange" in Japanese, but maybe they should rename the antenna to Funtenna, since it was really fun to build and use. The antenna was used for portable use, a couple of years, and was finally given away to an italian radio amateur visiting Norway in a camper.

Last winter I found one of my old logbooks, where this antenna was scetched on the back. So decided to obtain  the needed formulas, and make this calculator software. The original scetch indicated the antenna dimensions for 50.1 MHz to be 1m wide and 3m high, which coincides well with the dimensions given by the calculator below.