Thread: Does a UHF antenna base need to be earthed?

If you are using a ground independent antenna its not a problem but if not then you need a good earth

How do I know if I have a ground independent antenna. They just long black rods to me.

Google ground independent antenna - select images. You'll be able to figure out what you've got.

For instance, when fitting a antenna onto a fibreglass structure ( like a boat ) with a antenna base that requires it to be grounded to work, a ground can be made by using counterpoise wires.





These wires are generally tuned to the highest frequency of the transmitter, using a device called a dip meter.



A ground independent antenna has the function that a counterpoise offers already built into it.

UHF ground independent antenna picture - Google Search
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A ground plane independent antenna still needs its base earthed properly .
but Dosent require a bonnet or roof to act as a ground reference plane for the RF signal .

I was having range issues with my AM CB (ground plane independant) and UHF PRS ( ground plane dependent ) due to the poor electrical conductivity of the Aluminium body panels .
I ran an separate earth from the battery and earthed both the head units and antennas to it , which resulted in a massive increase in range.

Originally Posted by Ferret

How do I know if I have a ground independent antenna. They just long black rods to me.

If it still has the shrink wrap/sticker around the bottom see if gives you a model number or it may say if it is ground independent

Originally Posted by UBZ

I ran an separate earth from the battery and earthed both the head units and antennas to it , which resulted in a massive increase in range.

Ideally the earth for radio equipment where the antenna is also grounded should be appropriately fused so that if the vehicle's main earth fails, the radio equipment doesn't try provide the earth path which could result in a fire.

The main reason to earth the antenna end of the outer shield of the coax antenna cable is to reduce RF interference.

If the antenna is on a bullbar and the antenna cable passes through the engine compartment , then for sure both ends of the shield must be earthed .

If however the antenna is on the roof or gutter and there are no RF interference sources close by the route of the cable, then the earth to the radio, which then should have a good earth may suffice. The outer shield of the antenna cable has to earthed to the base of the antenna.

My gutter mounted ground plane dependent antenna does not have an earth and works fine with good range and no RF noise to speak of.I just didn't want to break the paint layer again.
Regards Philip A