mounting a ground dependant uhf aerial

[odarprado Lurker Find all posts View Profile Close odarprado]

I've recently purchased a small ground dependant 3db UHF aerial suitable for fitting to a gutter mount. I'm new to the whole UHF radio game and would appreciate some advice on the simplest and mostt effective way of earthing it effectively to the car body without upsetting paint, bodywork, sanity?

[samo Addicted PP Member Find all posts View Profile Close samo]

Re: mounting a ground dependant uhf aerial

run a seperate earth wire along side your antenna cable back to an earth in the engine bay or under the dash, some where it is easy to get to. cheers samo

[odarprado Lurker Find all posts View Profile Close odarprado]

Re: mounting a ground dependant uhf aerial

Thanks Samo, that makes sense. Regards Chris

[ozwapet2 Advanced Member Find all posts View Profile Close ozwapet2]

Re: mounting a ground dependant uhf aerial

The correct term is actually ground-plane dependant which means it needs to be mounted in the centre of a horizontal metal plate ( or grid ) to work effectively . A flat sheet of metal 0.5 to 1 metre square is the most effective ground plane at UHF ( that's why ground plane dependants are commonly mounted in the centre of the roof. )

If you mount it somewhere where it is not on sheet metal it won't work ( radiate ) properly. Adding a seperate ground wire isn't really going to make any difference to how it works at RF, as it is already electrically gorunded through the coax sheath anyway.

A ground plane dependant is normally just the small base with a whip. Are you sure you didn't mean you have a ground plane "independant" ? If that's the case, then the ground plane is built in to the antenna base in the form of a metal tube ( imagine the flat plate coiled up into a tube and you get the picture ). You can mount these anywhere.

[Bushbasher Out of control poster! Find all posts View Profile Close Bushbasher]

Re: mounting a ground dependant uhf aerial

Ahh, reminds me of my old army days and Radio Telephone Procedure and Antenna Wave Theory.

[odarprado Lurker Find all posts View Profile Close odarprado]

Re: mounting a ground dependant uhf aerial

Just to close this off - following the comments from ozwapet2 - I revisited my source of information on 'ground dependant' - a recent issue of 4wd Monthly where they reviewed a group of UHF radios. That's where I got the term from - however - it seems clear in hindsight (why always in hindsight?) that they mean ground plane dependant even though they don't say so. I took the cute little 3db aerial back and purchased a ground plane independant aerial and a bonnet mount and fitted that up instead. Regards Chris