My main HF antenna is a multiple 1/4 wave vertical stealth antenna supported by a tree in my back garden. This is the ideal stealth antenna for HF as it is almost invisible and does not require an ATU. The PDF attachment shows how it was originally constructed and the diagrams on this page show its latest stage of development.
Click on drawings for a better view
Teminal box wiring
The drawing above shows the terminal box comprising RF socket, loudspeaker spring connector and wire tuning loop. The loop is optional but does make tuning easier, as the loop is easier to trim than the antenna elements. When the minimum SWR is detected through adjustment of the tuning loop length, the radiating element length can be set accordingly.
I have added a loading coil to my antenna (as shown above) to enable operation on 40m. This can connect onto the loudspeaker spring terminals in place of the tuning loop.
Greg K3ANG has suggested a modification to the design which will allow it to be used when there are no suitably spaced branches on the supporting tree.
See the link at the bottom of this page for more details.
Here are some links to other antenna designs that operate using similar principles:
ON3JT has built an antenna following similar principles. Click here for details.
http://techdoc.kvindesland.no/radio/antennas/20061010171407551.pdf - from LA9ZV not in English but the pictures speak for themselves.
http://sites.google.com/site/trapantenna/about-the-antenna - This one from VE3HKY adds an inverted L for the low bands.
http://www.hamuniverse.com/hc4w4bwsgroundplane.html - Another variation from HC4/W4BNS on the Ham Universe web site.
I have also been experimenting with a magnetic loop design using Heliax coaxial cable for the main loop. This is still at the experimental stage but most of my ideas are based on the excellent magnetic loop site created by KI6GD. You can see the antenna on my QRSS beacon page.