collinear antenna + ground plane?

[pogbobo]

check out this antenna ...

http://www.radiooutfitter.com/b4505c/antenex/p98387.html

does it need a ground plane if it were to be used as a base antenna? and if so, what length should the radials be?

if you put a 1/4 wave uhf antenna on a ground plane you would use roughly 6" radials, b/c the 1/4 wave would be roughly 6" also ... but this thing is like 32" tall ... would you just use 1/4 wave radials anyway?

shed some light on me

 

[fredg]

Yes you want a ground plane... I am doing the same thing with a Larsen 2/70 mobile antenna, much like the one you are looking at, mine has a 33" vertical element.

I used the Atenex Mobile-to-Base converter for VHF/UHF.

http://www.monstermarketplace.com/Electronics/Landing1154a719.html

The picture on the website is a 800MHz converter, the VHF/UHF ground plane radials are 22" long and stick straight out. Here is a bad pic of my setup:

 

[pogbobo]

thanks for the info and pic

 

[prcguy]

Mount it in the center of a pie tin and it should be fine for UHF.
prcguy

 

[pogbobo]

sweet! gives me an excuse to eat a whole pie! haha

 

[N1BHH]

I made a quarter wave UHF ground plane out of a PL259 and #10 wire for the vertical and mounted it on a scrap metal plate and it worked fine. That's long ago and gone. An effective ground plane should be minimum of a quarter wave in radius, at UHF at least 6 inches.

 

[fredg]

thanks for the info and pic

The instructions that came with the ground plane kit indicated that you could cut the ground plane radials down to 6" for UHF only.

EDIT:
I actually looked at the instructions again... here is what it says:

Note: For 406-512 MHz cut radials to 8 inches.

 

[pogbobo]

but, I'm wondering if longer (longer than 1/4 wave) ground radials would work better with a collinear antenna ...... hmmm