UHF Aerial mounting on bullbars

hi mepvic

I have a D-MAX with ARB steel winch bar. Same mounting holes as you.

When I had TWO antennae fitted (UHF and 3G) they mounted both on the nearside - one in the ARB hole and the other with a U clamp. The reason they said was so I didn't have antennae in my face whilst driving.

First trip SWMBO complained about the antennae wobbling (TSV to CNS trip) so I cut some 25mm black poly pipe and slid over the spring base then some black tape to stop water collecting inside. It seems to be OK now but with hindsight I think I would have used two U clamps right over to the left side.

mal

We had an aerial mounted on a GME bracket fixed with U - bolts to the bar on a Prado with ARB bar. After about 1000km on outback corrugations the bracket broke apart (stainless steel plate snapped right at the 90 degree bend).

The aerial is now mounted on the LHS on the pre-drilled holes. No bracket - one less thing which can break.

With the pre-drilled hole at the bottom you lose signal as it's being shielded by the bullbar, bonnet, car bady etc. With being mounted up higher you should get slightly better reception.

AFAIK it's illegal to mount aerials on the RHS due to visbility. I could be wrong though.

If you mount your antenna on the bottom part of your bullbar you will increase the SWR ( standing wave ratio) of your antenna set up. This is very bad.

I have a SWR meter and tried it with the antenna on the base of the bull bar. I got a SWR of 2.8. Then I moved it to the top rail and the SWR went down to 1.1

On the SWR scale for UHF's, 1 is fantastic, 1.2 - 1.5 is ok, 1.8-2.0 is getting to be a problem, 2.5-2.9 is a big problem and at 3 or more you should not transmit as it may cause harm to your CB.

To give you an idea, at SWR 2.8, of the 5 watts, 3 watts bounce back to the UHF and only 2 watts are transmitted to the air. Ie it's like you have a 1 - 2 watt CB or less.

So the con's are that you will reduce your range by up to 60% and could you wreck your UHF. Apart from that it is fine ;-)

Hi

Need to be careful with aerials on the bullbars of Prado's. Because of the way the suspension is fitted, there is more movement in the BB and many "normal" antenna can't hack it. Ours snapped off on the GRR. The worst ones seem to be the single spring at the bottom type. When we spoke with a dealer in Broome he said to use a double spring model. Did this and all is OK to date. Moral of the story Make sure you talk to a auto electrician that knows how hard these things will work on rough roads

I originally had a Toyota bullbar on my Prado with the UHF aerial mounted on the top loop. When I changed to an ARB bullbar I mounted the aerial in the predrileld hole on the bar.
I have had no noticable change in UHF performance.

Leachy

I've heard it's a good idea to scrape a bit of the paint away from the pre-drilled holes on the bull bar antenna brackets, to ensure a good ground/connectivity.

Getting the antenna as high as possible is a plus. Getting it off the bullbar, and perhaps mounted on a gutter or roofrack even better, but then ya need to keep an eye on the overhanging branches.

Hi Mepvic,

Ive got a ground independent aerial and I mount mine on the bar tubing. Mine has gone down some rough corrugated tracks and has never once broken. It has been installed for at least 11 years.

Cheers Wilko

One thing I was told years ago, so not sure if correct today, is that the brackets can give you more choice in mounting aerial wire away from any electricals under the bonnet that may cause interference.

I reckon there are often better solutions than bullbar mounting such as gutter, roof or roofrack mounting.

In my limited experience of these things I have found my short gutter mounted antenna gives better and more consistent transmission and reception than most bullbar mounted antennas. On the CSR I noticed many vehicles, with bullbar mounted antennas, were more or less radio blind to the rear. They could only copy at quite a close distance. Others with bullbar mounted antennas had good coverage. What made the difference I don't know. Many times I was the lead vehicle and could communicate with other groups a long way to the rear when closer vehicles could not even hear them.

A short roof or gutter mounted antenna is also likely to be more trouble free than a bullbar mounted antenna.

Flynnie

Thanks to all for your replies. Interesting cross section. Think I will reuse my spring loaded base on the tubing. Have had it there on other vehicles and not had any problems with reception. Done some rough tracks and trips without any damage. Have noticed that the bullbar on the Prado does move a bit so will be interested to see how the aerial vibrates on the bar. Heading over to WA in a week or so. Should be a good test. Thanks again.