Thanks for sharing the pix.

The device I had in mind was built in a similar sheath folded back way -
but with more fiddling:
the shield is disconnected at the fold back point. The center conductor
goes to one quarter wave leg: the INNER shield goes to the other
quarter wave leg. The OUTER shield is left open at its end, but a
quarter wave back, it is connected to the regular shield.

This arrangement is intended to provide a quarter wave match to coax
over the band of interest. Stoppers might well help at the junction of
the two sheaths. Getting the lengths right is the name of the game.

Brian W

Wayne Paul wrote:
Here is an antenna I built last year for a friend's PIK-20 sailplane. The glider is one of the early fiberglass designs. (http://www.soaridaho.com/Antenna/index.html)

Later when doing a minor repair the owner was surprised to find an antenna of the same design inside the vertical stabilizer. It was also is a 1/2 wave length center fed; however, made out of two sections of 3/4 inch aluminum tubing. The coax was routed up through the lower tube to the feed point. The coax only extended about 6 inches below the bottom antenna section and was terminated by a BNC fitting.. There wasn't any indication that the antenna had ever been used.

Wayne
HP14 N990
http://tinyurl.com/N990-6F



"brian whatcott" wrote in message ...
RST Engineering wrote:
But since we aren't trying to squeeze the last fraction of a dB out of
the arrangement, and even though a balun still guarantees SOME
reflected power except at the precise center frequency of the antenna,
then simply connecting the dipole ears to the coax and stripping the
reflected power from the sheath with single-turn chokes in the form of
ferrite beads slipped over the coax right at the antenna does a
credible job of making a simple, lightweight, and nearly bulletproof
antenna.

Jim
Which reminds me, one old time method of matching a balanced antenna to
a co ax feed was with an extra coax matching section so the center
conductors connected to each half of the dipole, then the coaxes were
joined appropriately.

Probably too mutch fiddle factor, but rather than stoppering the base of
the dipole with ferrites, what would happen if you placed the stoppers a
quarter wave back on the coax? I never tried this out, but it's just
possible some of that extra gain might get into the coax?
Did you ever try this arrangement?

Brian W