Howdy Dan:
Thanks for the info on "Mobile Vhf Ant.pdf", very interesting stuff.
I was checking out the rest of your site, and found an interesting pdf on the "Skeleton Sleeve Antenna",
and it's similarity of the J-pole, and you state that the distance from the 1/4 wave elements, and the 1/2 wave
element is not that critical. I have heard this before about the elements on the J-pole too, but what I don't understand
is why this dimension is not critical, it is an electrical path that should be subtracted from both elements, right?
Is it correct to shorten both elements by 1/2 of the dimension between the elements?

--
SeeYaa Harbin Osteen KG6URO

!sdohtem noitpyrcne devorppa-tnemnrevog troppus I




"Dan Richardson" wrote in message ...
On Thu, 2 Mar 2006 10:56:15 -0600, (Richard
Harrison) wrote:

Action of a common ground plane is different. When its balanced radials
are perpendicular to its whip, radiation from its radials zeros out
leaving the whip to do all the radiation. Ideally, a whip mounted on a
vehicle or directly on the earth behaves the same. It is the whip which
radiates.

Boy Richard, you sure missed the boat on that one!

Roy is quite correct in stating that a vehicle's body behaves as one
side of a dipole. A lopsided dipole to be sure, but one half the
antenna just the same.

A number of years ago I did a study using NEC modeling comparing VHF
mobile whips (1/4, 1/2 and 5/8-wavelength) mounted on different
vehicles. I created wire frame vehicles models for a full and mid-size
passenger cars, a small pickup truck and an SUV. The results for the
same antenna mounted top-dead-center on the different vehicles was
quite noticeable sometimes substantial.

An article I wrote on the subject can be viewed at:
http://k6mhe.com/files/mobile_vhf_ant.pdf

73,
Danny, k6MHE







email: k6mheatarrldotnet
http://www.k6mhe.com/