Can anyone tell me if you change the shape of a given antenna, will it
change the chararistics?

I.E.:

I have a 3 element 50 Mhz yagi on a 6 foot boom.

I want to mount the antenna in the back of my pickup-truck and if I bend the
elements down the antenna will fit within the confines of the truck (in
other words not stick out into the other traffic lanes). Therefore I can
still mount the antenna about 8ft off the bed of the trk and to keep it from
falling off I can guy it to the trk.

73's

yes, it will. how much is hard to guess, but i would say probably not as
much as mounting it a few feet off a metal truck bed with a cab in front of
it.

"Howard W3CQH" wrote in message
...
Can anyone tell me if you change the shape of a given antenna, will it
change the chararistics?

I.E.:

I have a 3 element 50 Mhz yagi on a 6 foot boom.

I want to mount the antenna in the back of my pickup-truck and if I bend
the elements down the antenna will fit within the confines of the truck
(in other words not stick out into the other traffic lanes). Therefore I
can still mount the antenna about 8ft off the bed of the trk and to keep
it from falling off I can guy it to the trk.

73's

On Mon, 10 Mar 2008 17:49:56 -0400, "Howard W3CQH"
wrote:

I have a 3 element 50 Mhz yagi on a 6 foot boom.

Hi Howard,

Model it with the free version of EZNEC.

(The easy answer is "of course it will affect it.")

73's
Richard Clark, KB7QHC

Howard W3CQH wrote:
Can anyone tell me if you change the shape of a given antenna, will it
change the chararistics?

I.E.:

I have a 3 element 50 Mhz yagi on a 6 foot boom.

I want to mount the antenna in the back of my pickup-truck and if I bend the
elements down the antenna will fit within the confines of the truck (in
other words not stick out into the other traffic lanes). Therefore I can
still mount the antenna about 8ft off the bed of the trk and to keep it from
falling off I can guy it to the trk.


yes, it will change the characteristics (potentially a lot)

You can model it in EZNEC, NEC, etc. and get a feel for how much.

However, gut feel... the elements are about 3 meters long, right? (1/2
of 6 meters. that's about 10 feet? And you want to make the antenna
have elements that are, say, 7-8 feet long?

Assuming you can load the elements appropriately so that electrical
properties work out, the performance of the 3 element yagi with 8 foot
elements in a truck bed will be pretty comparable to the 3 element yagi
with 10 foot elements in a truck bed. If it were 3 dB different, I'd be
surprised. If it were 0.5 dB different, I wouldn't.

either way, the truck body is going to significantly interact, and
that's going to be a big factor.



73's

On Mon, 10 Mar 2008 17:49:56 -0400, "Howard W3CQH"
wrote:

Can anyone tell me if you change the shape of a given antenna, will it
change the chararistics?

I.E.:

I have a 3 element 50 Mhz yagi on a 6 foot boom.

I want to mount the antenna in the back of my pickup-truck and if I bend the
elements down the antenna will fit within the confines of the truck (in
other words not stick out into the other traffic lanes). Therefore I can
still mount the antenna about 8ft off the bed of the trk and to keep it from
falling off I can guy it to the trk.

73's


http://www.moxonantennaproject.com/

http://www.cebik.com/fdim/fdim7.html

This doesn't answer your question, but it may give you some
alternative ideas. I think the top link, the Moxon antenna, may
relate somewhat to what you are looking for. The lower link may give
you some "shortened beam" ideas.

I hope you find a solution.
Buck
N4PGW
--
73 for now
Buck, N4PGW

www.lumpuckeroo.com

"Small - broadband - efficient: pick any two."