Shape
 

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

Shape
 

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

Shape
 

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

Shape
 

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

Shape
 

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."