"RST Engineering" wrote in message ...
One big problem right off the crack of the bat. "Folded" dipoles have a characteristic feedpoint impedance of
something on the order of 300 ohms. A standard dipole at the center of resonance will have a characteristic feed
point impedance of something on the order of 72 ohms.

The mismatch for a 50 ohm radio (without some sort of a transformer) to 300 ohms is a hell of a lot more than 72 ohms.

Somebody posted that a folded dipole has a broader bandwidth than a straight dipole. I do not believe that to be
true. The main use for folded dipoles without transformers was in the 1950s when we made them out of twinlead and fed
a TV set with them. TV sets in those days were designed for 300 ohm antennas.

Get yourself a 3/8" diameter wooden dowel 48" long. Get two pieces of copper tape 21.5 inches long. Glue the tape to
the dowels so that there is a 1/4" gap in the center of the dowel between the pieces of tape. Run the tape out as far
as it will go towards the end of the dowel. You should have about 2" of bare dowel at each end of the dowel.

Drill an 1/8" hole into each of the pieces of tape right at the center ends of the tape. Take a piece of 50 ohm coax
cable (RG-58 from the spool in the back of the Radio Shack store) and peel back the black outer jacket for an inch.
Now fish the center white/clear insulator through the braid by means of an icepick or similar tool. Twist the braid
tightly and poke it through one of the 1/8" holes. Solder the braid to the copper foil. Strip the white/clear
insulation from the center conductor for about 1/4". Poke the center conductor/insulation through the remaining 1/8"
hole. Solder the center conductor to the copper tape as it exits the hole.

As close to the braid as possible, run a tie-wrap around the black outer sheath of the coax and fasten it securely to
the dowel. Now run that coax at right angles for at least a foot or two before snaking it around through the
airframe.

You've got two inches on either end of the dowel to nail, screw, glue, or otherwise fasten your dipole antenna to one
of the fuselage formers aft of the baggage compartment. Keep the TIPS of the antenna as far away as you can from any
metal.

Some refinements: A balun is always a good idea when connecting a BAL anced antenna (dipole) to UN balanced coax
cable. You can do this with little tiny chunks of powdered ferrite called toroids, or you can do this with a coax
"split-tube" design. Both are a little beyond the scope of a newsgroup article.

Since I absolutely refuse to use the newsgroups to pimp my own goods, will somebody else please tell this fellow where
he can get copper tape, toroids, and the illustrated book that shows how this all works?


Jim




I've seen all this stuff he
http://www.rst-engr.com/rst/catalog/...e_antenna.html

;-)