Fiberglass roof on FJ-40
 

Howdy Y'all:

I have a fiberglass roof on my Landcruiser, and I was wondering if I can use a halfwave roof mounted antenna?
For some reason, I think since the halfwave is end loaded, that it will not work on my fiberglass roof, and that
it uses a steel roof as part of the match. Am I wrong here? The only other thing I can think of is some kind of
stainless steel J pole on a mount coming off the back. And what about a dual band that will work on fiberglass?
Anybody work with this problem before?

SeeYaa:) Harbin

Fiberglass roof on FJ-40
 

On mine, I mounted a telescoping BC band replacement antenna at the top
of the metal body piece just behind the door and collapsed it down to
about a quarter wave on 2 meters. Although you could probably fiddle the
antenna length to get a fair match, I built a little highpass T network
out of an inductor on a small powdered iron core and a couple of trimmer
capacitors to do the matching. The pattern is probably pretty skewed,
but it's adequate to reach the local repeaters. You could mount a dual
band antenna at that same spot with some sort of right angle mount.

A half wave antenna at the top of the roof should work ok, but even with
a half wave antenna, there's a small amount of return current that has
to go somewhere. If I were willing to punch a hole in the top (which I'm
not -- have you seen what a replacement top costs?), I'd do something
like put a small ground plane inside the car against the top.

This might be a reasonable application for a through-glass antenna --
through one of the windows, that is, although it might be interesting to
see how one would work as a through-the-top antenna if you could rotate
it to be vertical. But having spent quite a few hours studying various
patents for their design, it looks like some might work much better than
others.

Roy Lewallen, W7EL

Harbin wrote:
Howdy Y'all:

I have a fiberglass roof on my Landcruiser, and I was wondering if I can use a halfwave roof mounted antenna?
For some reason, I think since the halfwave is end loaded, that it will not work on my fiberglass roof, and that
it uses a steel roof as part of the match. Am I wrong here? The only other thing I can think of is some kind of
stainless steel J pole on a mount coming off the back. And what about a dual band that will work on fiberglass?
Anybody work with this problem before?

SeeYaa:) Harbin

Fiberglass roof on FJ-40
 

"Roy Lewallen" wrote in message
...
... But having spent quite a few hours studying various patents for their
design, it looks like some might work much better than others.

Roy Lewallen, W7EL


Roy,

Would you share with us which ones you think would work better?

73,
Bob AD3K

Fiberglass roof on FJ-40
 

Bob Spooner wrote:
"Roy Lewallen" wrote in message
...
... But having spent quite a few hours studying various patents for their
design, it looks like some might work much better than others.

Roy Lewallen, W7EL


Roy,

Would you share with us which ones you think would work better?

73,
Bob AD3K

Sorry, it's been nearly 20 years since I went through the patents, and I
don't recall all the various modifications and innovations I came
across. And I don't have any idea which might have been included in
commercial designs. Surely someone has done some comparative
measurements of various commercial units and published the results. If
not, it sounds like a good project for someone interested in using
through-glass antennas. I'm not one of them.

Roy Lewallen, W7EL

Fiberglass roof on FJ-40
 

A half wave antenna will work just fine. Several antenna manufacturers
make them for just the type vehicle you have, corvettes,boats etc.

73
Gary K4FMX

On Mon, 20 Feb 2006 16:08:49 -0800, "Harbin"
wrote:

Howdy Y'all:

I have a fiberglass roof on my Landcruiser, and I was wondering if I can use a halfwave roof mounted antenna?
For some reason, I think since the halfwave is end loaded, that it will not work on my fiberglass roof, and that
it uses a steel roof as part of the match. Am I wrong here? The only other thing I can think of is some kind of
stainless steel J pole on a mount coming off the back. And what about a dual band that will work on fiberglass?
Anybody work with this problem before?

SeeYaa:) Harbin

Fiberglass roof on FJ-40
 

How about a ground plane kit for vehicles? It consists of a rool of
aliminum foil tape about 4 inches wide. Does the vehicle have a head liner?
If not make a big "X" with the stuhh and mount the antenna in the middle.You
can get one of these kits at buisness band radio repair shops