Vinnie S. wrote:
On 22 Dec 2005 18:45:44 -0800, wrote:


Hi, I am looking to build an antenna for CB band... It will be going up
in my attic with about a 19 foot ceiling. I would like to have it free
standing as I have no way to get to the top to hang a wire type
antenna...

here is what I was thinking of doing:

I was going to biuld a 1/2 dipole but out of 1/2" copper pipe using PVC
pipe as insulators for the center and bottom and building some kind of
wood base for it.

will this work the same as a 12g wire dipole? do I still make each
side 8' 5" long or will this change? Does it matter what side is up?
any tips or ideas?

thanks
Jim



Jim,

Here is the site for the homemade 1/4 ground plane. The pipe would work better
here. So would rigid solid copper wire. I think this is a better option for
local talking. The dipole would work better for DX.

Whatever you do, keep it the hell away from any kind of romex or AC wiring. It
will induce some noise. I had a similar problem because of that. But you are
better off with a 19 foot attic. Get the antenna tip to the top of the roof.

Vinnie S.

The unbalanced 1/4 wave GP will match to the CB better then a balanced dipole.

Coax is unbalanced. It's a hot and a shield. Dipoles need equal and opposite feed.

You need about 8.6 feet per element.

http://www.monsterfm.com/engineering/antcalc.htm

I built the yagi at arrl.org, 7db for 7 bucks.
Works damn good for being made of coat hangers and a 1x2!

I tried to build CB antennas. They are BIG. 2 meter antennas are much smaller.
VHF-FM has much better local range then 11 meters. I use part 95 and 97 all the time.

I may have to try one of these for 2 meters and another for 430 MHz ATV.
http://www.softcom.net/users/kd6dks/quad.html

Yagis are simpler to build, but I'm told quads have better gain.
Quagis have quad feeds and yagi elements. I need to bug Jay for
some good matches for coax to balanced feed units.

Another ham mentioned that the shorter director is capacitive
and the longer reflector is inductive. The lead/lag of the
elements causes the waves to constructively add in one direction
more then others.