I live in house on a small lot in a dense urban neighborhood with few opportunities for antennas. I decided to put up an antenna for the higher HF bands in the highest structure available, a mature maple tree. I wanted multiband coverage, which would be simple with an open-wire balanced feeders, but there is no easy way to run open wire feeders to my shack in the basement.
Inspired by the G5RV designs, I aimed for an antenna that could cover 20/17/15/12/10 meters with coax feed. Playing around with EasyNec, I came up with a design that uses 75 ohm cable, and keeps the SWR under 10:1 over the 5 bands, which keeps the cable losses reasonable.
The picture below shows the details. The antenna is made from Radio Shack stranded hard-drawn copper antenna wire. Each half is 13 feet long, for an overall length of 26 feet.
The antenna is installed 45 feed up from the ground in the tree. The feed arrangement is stapled to the trunk (on the side facing away from the street HI). The wires are each held out by sections of elastic that are in turn anchored to the branches of the tree by steel anchor shaped gadgets made from coat-hanger wire.
The wires were hung in the tree by throwing a ball with string out from the trunk. At the ground, the wire/elastic/anchor was attached, and pulled back up into the tree by the string.
The G5RV-style matching section is made from two pieces of of 75 ohm RG11/U each 7'3" long. This acts like a section of 150 ohm balanced line, but it has the advantage that it can be stapled to the tree trunk.
The matching section is fed by RG11/U 75 ohm coax that has a ferrite bead balun on it where it joins the matching section.
The coax runs 73' to my shack in the basement, where it is tuned by an EF Johnson 275 watt matchbox. The matchbox tunes it 1:1 over all the 5 bands. I did have to add an extra 6' to the feed line to achieve this behaviour. While I usually run low or moderate power, I have had no problems with my occasional use of 600 watts PEP (i.e., the tree has not yet burst into flames HI).
I have really enjoyed using this antenna, it performs about the way I would expect for a dipole at 45 feet up, which is not a bad antenna. It has the advantage of being very low profile. Even in the winter with the leaves off the tree, you need to look pretty hard to see the antanna among the branches - it is invisible from the street.