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