first heard about Full Wave Loop antennas about 1984, when a friend of mine in Seattle commented favorably on a pair of them that he'd hung.  He described the setup he used as a full wavelength of wire hung in a Delta (triangular) configuration, and using an electrical quarter wavelength of 75-Ohm coax at the feed point to match the nominally 100-Ohm impedance at resonance with 50-Ohm cable.  His 80-meter loop was fed at the top, and his 40-meter version at the bottom.

When I decided I needed to replace my failing 80/40-meter trap dipole for everything above 80 meters (because the trap capacitors had failed), I decided to try what he'd done with the 40-meter loop.  That went up on my tower in the Spring of 1986, and per-formed fairly well on 40, 20 and 15 meters.  Loading it on 10 was tricky and probably not entirely successful, and it wouldn't play at all on any of the WARC-79 bands (30, 17 and 12 meters).  It did get up an honk on 6 meters, where it was a 7-wavelength loop, however.

That antenna lasted for about 15 years, plus or minus repairs to compensate for tree surgery and corroded wire.  By the end of its service life it was apparent that some things needed to be done differently in order to make it truly functional on everything between 40 and 10 meters.

The inspiration for the next step came at SeaPac 2002 where we hung a 40-meter loop from the flagpole at the beach house we were renting, with an SGC auto-tuner at the feed point.  I didn't have the means to purchase one of those gems (still don't), so I looked at less-expensive alternatives.  Until we replaced it with the ZL Special 20-meter beam on Field Day, we'd been using an 80-meter loop fed with ladder line as the 20-meter CW antenna.  Therein lay the solution:  450-Ohm ladder line is much less expensive than coax, and is almost loss-free at HF.  I have an old MFJ-941B tuner, which while it is not optimal, will work.  Getting the feeders out of my basement and up to the antenna was not a really big deal:  I bored a couple of holes an inch or so apart through the outside wall, cut the webbing out of some ladder line, and sealed the holes around the wires with Coax-Seal.  Splicing ladder line is a lot easier than doing it with coax.  This was a whole lot easier than some things I've tried over the years.

My current loop is strung as a tilted,  almost symmetrical Delta, with the ladder line feed at its apex, about 40 feet up.  It tunes everything between 40 and 10 meters with ease, and I have gotten it to load at less than 2:1 SWR on 80 (although I have a low dipole for that band).  Unfortunately, it won't load at all on 160.

Construction is dirt-simple:  The active wire length in feet is figured nominally as with a standard quad loop:  1005/f, where f is the center frequency of interest on the lowest band, expressed in MHz.  Insulators can be anything that will block the flow of current, although ceramic or plastic end insulators are preferable to egg types which are for strain relief.  The feed point should be as high as you can get it:  I have a 44-foot tower (the top of which has never been graced by a beam), but tall trees work very well, too.  The antenna can be hung as a delta or a rectangular loop or a diamond, it matters little.  Equally uncritical is the plane in which it is suspended.  Feeding it at the top or bottom gives horizontal polarization, and mid-side would make it a vertical.  The nice thing is that dimensions are pretty uncritical... a non-resonant length of wire will work almost as well (and in the case of mine, does quite well on the WARC-79 bands).

In these recent times of sunspot maximum, 50 watts of PSK-31 or RTTY can usually make itself heard throughout the world, wherever the band is open.  It also holds its own in CW contesting at 100 watts and probably would also on SSB or SSTV.

-AL7W