wrote:
Cecil Moore wrote:
Lots of hams use vertical coaxial-sleeve dipoles
with the coax feedline running up through the sleeve.
Lots of hams prefer end-fed antennas. Does anyone run
his coaxial-sleeve dipole horizontally?
--
73, Cecil http://www.w5dxp.com

Those antennas have poor decoupling from the feedline,
unless you use decoupling devices of some type. I once
made one of those for 2m. In general, it was horrible when
using it with no decoupling. If I run a vertical half wave, I
actually prefer to base feed it, if I'm going to run it with no
additional decoupling sections. I would never end feed a
horizontal wire antenna unless it was a last resort. If I did,
I probably wouldn't even bother with trying to center feed
it like the coax sleeve antenna.
A vertical coax sleeve antenna needs cones, radials, chokes,
etc at the proper points on the feedline. Usually two sections
if you want good decoupling. The sleeves are probably the
most popular of the commercial versions.
If I ran an end fed half wave, I don't think there would be a
drastic difference between feeding from the end, or feeding
from the center with the coax sleeve version. Both have
their problems. If I run a dipole, I feed it normally from the
center, and the line runs away perpendicular to the wire.
IE: normal config.. The average 1/4 wave ground plane will
usually outdo a coax sleeve 1/2 wave, if the 1/2 has severe
common mode problems. This was the case on 2m for sure,
and it's most critical there. I never ended up using that coax
sleeve halfwave. My 1/4 GP smoked it on 2m.
MK

I have good performance out of a sleeve antenna on vhf where the
sleeve was quite a bit larger tahn the coax running up the middle. RG
58 inside 1-1/4 inch sleeve. This was on a vertical antenna. Ferrite
beads aided in decoupling the coax, small bits of styrofoam were used
to keep the coax centered in the sleeve. Antenna was supporte by
placing it in a fiberglass tube. I could see how this could be a real
PITA to do horizontally.

JIMMIE wrote:


I have good performance out of a sleeve antenna on vhf where the
sleeve was quite a bit larger tahn the coax running up the middle. RG
58 inside 1-1/4 inch sleeve. This was on a vertical antenna.

They are good antennas if decoupled. Many have been used for
commercial/public service systems. A company called "Dodge" ??
used to sell a lot of them. Real heavy duty construction.. Their
version used two stacked sleeves. You could also use stacked
radial sets.
MK

Hi Cecil

If I have understood well your question, I think that the "Resonant
Feed dipole" (ARRL Handbook. 1996, page 20-17) is so much similar to
the clasical sleeve antenna. See in http://www.io.com/~n5fc/rfd.htm a
description.

Decoupling with his approach (choke) to the transmission line is poor
due high end Z.

I have modified it replacing coaxial choke transforming it in a coil
(less turns) made with the same coaxial but parallel tuned with a
condenser making these turns resonate (both terminals of condenser are
connected on the braid).

It is a good kite antennna (I am flying today with a Rokaku kite), and
a good solution for a good "windows in" dipole, without any tunner
neither earth connection...

Best Regards

Miguel Ghezzi (LU 6ETJ)