TheRadioBoard

This antenna sounds nice, but would it actually work on 80m? I worry since I haven't come across this design anywhere else. Somehow it seems that the waves might cancel with the antenna folded back on itself, but I really know little about antennas.




EDIT: Shrunk pics.

Those images are big files! It looks something like two, short, phased verticals, with top loading. The text refers to low-angle radiation, so presumably there is significant vertical polarization. I think you'd want as much vertical wire as possible with this one. See the PDF article on the Bruce Array, here: http://www.antennasbyn6lf.com/2005/04/bruce_arrays.html for something similar. In the antenna you're considering, the bottom elements are probably phasing lines, the vertical elements are the main radiators, and the top elements provide capacitive loading.

73,

_________________

http://kr1s.kearman.com/
http://qrp.kearman.com/

Thanks for the info on the Bruce arrays. I can understand how this antenna would work like the Bruce arrays on 40m since the total lengths of the elements would be full wave, but on 80m I'm not quite sure. Maybe I'll try putting it up and seeing how it works.

Back in the 1990s, QST ran an article about a pair of full-wave loops that hung from a common support, but were physically 90 degrees apart. The idea was to use a DPDT relay at the base to select one or the other. An option was to use a second relay to open the loops at the top for use on other bands. I can't remember the name of the thing so I can't point to the article, but that's all the info you need to build one. They were squares, but standing on a corner.

I built one for 30 M, and used a couple of nice ceramic-based relays for switching. Fed with 450-ohm twin lead. Worked really well on 30-20-17-15 until I got an SB-220... Couldn't use the amp on 30 M (200-W limit here in the U.S.), but I drove the antenna on the other bands with the amp, using a KW Johnson Matchbox tuner. One day I noticed the SWR seemed flaky and closing the top relay didn't affect tuning on any band. Hmmmm. Yep, the open-circuit voltage on at least one band was high enough to destroy a very hefty relay. It was a gift from my late Elmer, and I was pretty bummed out!

The moral is, "one size fits all" antennas can have unpleasant anomalies. A half-wave dipole has pretty high voltage at the ends; I've observed that with a 40-M inverted vee here, driven with a kW. I zorched some shrubbery when I placed one end in the bushes to conceal the rope I was using to tie it down to the anchor (temporary installation). The Burning Bush would have taken on a whole new meaning if conditions had been drier.

Moxon, a Brit, had fun building antennas with the ends folded back. If you do an Internet search for "moxon antenna" you'll see lots of examples. I think an antenna like this would be easy to model, too, and that would give you some insight into the claims of low radiation angle, etc.

Okay, the ol' brain hasn't completely failed. The QST article was "Build the Versa Loop," and it was in the August 1989 issue (okay, I got the wrong decade....), p 22. There was a Feedback in the May 1990 issue concerning gain figures given in the article.

73,

_________________

http://kr1s.kearman.com/
http://qrp.kearman.com/

Thanks for the information!