Groundplanes

[BlackDragon]

Hi all,

This may have been discussed previously, although I'm struggling to find info. I decided to get creative and set up a mobile cb in my shed. Really happy, made a bracket for the side of the shed and receiving lovely signal. SWR through the roof. Of course I didn't think about the fact my shed is wooden. Is there a way to create a good enough ground plane for my antenna to work. I have tried making one of those ground plane extenders (with three rods that stick out) which seems to have dropped me to an SWR of around 2.5 on channel 1 and 40, however I'm not sure how these work, so relay I have 2 questions;

Firstly, the ground plane extender, do they connect to the antenna, or are they connected to the ground and isolated from touching the antenna?

Secondly, is there another way of making the ground better? It's a peaked roof so I can't really bolt on a sheet of metal.

Sorry for the long and gramatically inaccurate post, appreciate any help
Cheers

[Hair Bear]

Hi,
You don't say what antenna/mount system you're using.
A folded sheet of metal sat on the peak of the roof would help but not knowing what you have it's difficult to suggest.

[BlackDragon]

My apologies

I have used a piece of flat bar bent to 90° and mounted the antenna to that (coax centre to antenna and earth to the bracket. I have several basic whippy antenna but the one I have to is a twin coil thunderpole no longer on there website.

Does the metal plate not need to be flat? As I said I have got it down to around 2.5 by making the funny ninja star thing, but would like it lower if possible.

Thank you

[Hair Bear]

So the way I'm reading this is that you have a mobile type antenna, 3/8 stud base, with a stud mount into the gp. I don't see any reason why the gp would need to be flat, if you were to take a 6' x3' sheet, fold it down the middle and sit it on the roof with a screw in each corner it should work well. With a bit of jiggery pokery, you could put the metal on the inside of the roof and the antenna through a hole at the apex.
Alternatively, if you were to use something like an Antron99, it could be mounted at ground level beside the shed, give you 12' of gp then 6' of antenna on top as a single pole without horizontal elements and almost no tuning.