Rob Roschewsk wrote:
The sleeve idea sounds interesting.

Could I build it out of say aluminum tubing, run the coax up the center
of the tube to some sort of insulator, shield connected to the braid and
center connected to a wire extending upwards? Could I build the top half
out of tubing as well or does the radiator need to be significantly
smaller than the sleeve?

Cut two 1/4WL sections of tubing. Slip one over the coax and
connect it to the coax braid where the coax enters the
tubing. Leave the outer insulation on the coax. Don't connect
the bottom tube or the coax braid to anything where the coax
comes out. Install an insulator/support to hold the two pieces
of tubing together in a straight line dipole-like configuration.
Tie the coax inner conductor to the upper tubing. With this
configuration, you won't need additional choking on the feedline.

*******************+ ********************+
| ====================+========
1/4WL +--------------------------------- coax
| ====================+========
*******************+ ********************+

*** is the tubing, + is a connection.
--
73, Cecil http://www.qsl.net/w5dxp

Cecil Moore wrote:

Cut two 1/4WL sections of tubing. Slip one over the coax and
connect it to the coax braid where the coax enters the
tubing. Leave the outer insulation on the coax. Don't connect
the bottom tube or the coax braid to anything where the coax
comes out. Install an insulator/support to hold the two pieces
of tubing together in a straight line dipole-like configuration.
Tie the coax inner conductor to the upper tubing. With this
configuration, you won't need additional choking on the feedline.

*******************+ ********************+
| ====================+========
1/4WL +--------------------------------- coax
| ====================+========
*******************+ ********************+

*** is the tubing, + is a connection.

I don't understand how this would work. The tube to coax connection
on the right seems to extend the 1/4 wave tube indefinitely, down the
line. I think I would connect the coax shield to the right tube at
that tube's left end, and add a ferrite current balun around the coax
where it exits at the right end of that tube.

John Popelish wrote:
Cecil Moore wrote:
*******************+ ********************+
| ====================+========
1/4WL +--------------------------------- coax
| ====================+========
*******************+ ********************+


I don't understand how this would work.

Now that you mention it, neither do I. I just copied it from
the 1993 ARRL Handbook, Fig. 3, on page 14-4. I do know how it
works when feeding a balanced antenna. Let me redraw it with
one that I know works.

*******************+ +******************** choke
| +=================================
1/4WL +--------------------------------- coax
| +=================================
*******************+ +******************** choke
--
73, Cecil http://www.qsl.net/w5dxp

Yea that's what I was expecting you to say. I can remember seeing
descriptions of this "as if the ground plane is folded down around the coax"

I think I might try this ;-)

Thanks again all!

de ka2pbt


Cecil Moore wrote:
John Popelish wrote:
Cecil Moore wrote:
*******************+ ********************+
| ====================+========
1/4WL +--------------------------------- coax
| ====================+========
*******************+ ********************+


I don't understand how this would work.

Now that you mention it, neither do I. I just copied it from
the 1993 ARRL Handbook, Fig. 3, on page 14-4. I do know how it
works when feeding a balanced antenna. Let me redraw it with
one that I know works.

*******************+ +******************** choke
| +=================================
1/4WL +--------------------------------- coax
| +=================================
*******************+ +******************** choke

Cecil Moore wrote:
John Popelish wrote:
(snip)
I don't understand how this would work.


Now that you mention it, neither do I. I just copied it from
the 1993 ARRL Handbook, Fig. 3, on page 14-4. I do know how it
works when feeding a balanced antenna. Let me redraw it with
one that I know works.

*******************+ +******************** choke
| +=================================
1/4WL +--------------------------------- coax
| +=================================
*******************+ +******************** choke

That is what i was trying to describe, and makes sense to me.
Thanks for drawing it.