You are here : Installing CB Into 4x4's / Fitting the Aerial & Mount / Fitting a Bullbar/Roll Cage Mount
| Our Bullbar/Rollcage mount shown here with a 5m lead |
Installing one of our Bullbar / Roll Cage mounts is very easy...
What you need to do to install a Bullbar / Roll Cage mount :
Bolt it onto whatever bar or section you want to fit it to - making sure at least one part of the mount has a metal-to-metal connection with what it's bolted to.
(There is a way of getting an earth connection without making metal-to-metal connection at the mount - see the "Installing without metal-to-metal connection" section below)
You will need an SWR meter (a basic and easy to use test meter) to make sure you have a good earth between the mount itself and whatever you have fitted it to. If you don't have a good earth, you will have a very high SWR, and this can damage the CB, so to be sure you should check it with an SWR meter.
Most of our aerials (Springers etc) are about the right length to give a good SWR reading if all other factors are ok (some suppliers call this "Pre-SWR'd" which is rather misleading as a good SWR depends on a number of factors, not just the aerials length), but using the meter to check, and fine tune (usually by adjusting the aerials length) if necessary, as well as check that you have a good earth/ground plane, is essential.
Read our SWR meter guide.
Metal-to-metal earth :
You don't have to go mad with an angle grinder or file, but you will need to get a clean metal-to-metal connection between some part of the mount (this can be either the U-bolt or the bar part) and your bullbar or rollcage.
This metal to metal contact point only needs to be a few square millimeters, but if it is this small, make sure the the mount is not going to move over time, so it no longer touches metal.
| Here the customer went a bit over the top with getting a good metal-to-metal earth, but at least it's sure to make a good contact! | Here you can just see where the paint has been scraped away to make the earth contact... just a few square mm is necessary |
Installing without metal-to-metal connection :
If you cannot make a metal-to-metal connection at the mount, there are two ways you can still get this mount to work correctly for you :
If you choose to use an earth wire or earth strap to make the ground contact then the wire should be as short and thick as possible to get the best connection, and should be attached to the mount (not the aerial) - a ring terminal on one of the nuts on the U-bolt is ideal for this.
This method of obtaining an earth connection will work ok, but you will get slightly less range than if you had made the earth connection at the actual mount because the further the aerial is away from it's earth, the higher the angle of radiation will be - so you'll be sending signal up at something like 45 degrees, instead of a much lower angle, along the ground.
Using one of these methods is ideal if you have a nice new powder coated rack and don't want to scrape the paint away, or have a heavily chromed or zinc plated bar that again you don't want to scrape, or the surface of what you want to mount to is plastic coated.
| | Another Rollcage/Bullbar mount fitted with artificial ground, this time on a plastic coated mirror arm of a tractor |
Bullbar mounting :
In many cases the bullbar itself will be a large enough piece of metal to give the aerial an earth (remember, this earth doesn't need to be a "back to battery negative" earth, just a large piece of metal - i.e. the vehicles body to give the aerial a groundplane).
Generally speaking, the larger the groundplane is, the better the aerials performance will be - this is because the angle of radiation is lower (i.e. being transmitted along the surface, rather than straight up in the air) with a larger ground or earth, so you might find it useful to make sure there is a metal-to-metal contact between the bullbar and the chassis or wherever it's bolted on, so your ground plane is not just the bullbar, but the whole vehicle's body or chassis.
One of the factors that contribute to getting a good SWR is that the aerial shouldn't have too much metal close to it, so it's no good putting this mount right at the bottom of a bullbar, and having the aerial right next to the top bar etc, as this won't work so well - best to put it on the top bar to start with.
Bullbar mounts are subject to a lot of vibration, so you should make sure the nuts are tightened well, and you should keep a check on them for tightness.
| Mount fitted to the bullbar of a Mitsubishi Shogun/Pajero | |
Rollcage mounting :
Usually a rollcage, either full or half, will be plenty large enough to provide the aerial with a ground plane, but you will need to fix the mount somewhere so the aerial does not have too much metal around it, otherwise this will alter the SWR reading.
| Rollcage mounting - above the windscreen | Another rollcage installation |
| Bullbar/Rollcage mount fixed to a rollcage - fitted "points up" because of limited clearance between rollcage and roof | A photo of the same installation from a different angle |
Other places you can use this mount
Because this mount can be used on any round tube, it can be used to mount an aerial in a whole load of different places...
For example : - On a spare wheel carrier
- On a rear ladder
- On any round tube between 30mm and 55mm in diameter
| Swing away wheel carrier fitment on a late model Hilux Surf |
A further modification you could consider...
The photo below shows a bullbar/rollcage mount which has been modified slightly by the customer - he added a part of an exhaust clamp that "fills in" the other side of the tube, doubling the clamping force and making for a slightly neater install.
He also cut off the excess length from the ends of the U-bolt.
| A customer modified bullbar/rollcage mount |
General points to remember wherever you use the bullbar/rollcage mount :
Using this mount means you have the cable on the outside of the vehicle - it's important to secure the cable (with tiewraps) so it's not going to get tugged on by stray branches etc. Also, where there often ends up a "loop" under the mount where the plug connects - make sure you keep this as small as possible, maybe close the loop with some gaffa tape or similar, so branches etc can't snag the cable or connector.
The stud (the bit where the aerial screws in the top, and the plug goes in the bottom) that comes with this mount is a top quality american item, so you can get grips on it and really tighten it up. The stud's insulator (the bit that insulates the main bolt from touching the bar as it passes through it) is very tough nylon, so make sure this is tight.
This nylon insulator has a lip to it, which is designed to sit in the hole in the bar, so that the bolt that passes through it doesnt touch the bar at all - this is important so if you take the stud apart for any reason, make sure it goes back with the lip seated properly in the hole.
Product links:
Bullbar/Rollcage mount with 5m cable
4x4 CB Radio Package Deals (all of which have the option of choosing this mount)
More photos of the Bullbar/Rollcage mount
You are here : Installing CB Into 4x4's / Fitting the Aerial & Mount / Fitting a Bullbar/Roll Cage Mount
