Installing CB into a 4x4

The aim of this section is to give you the information you will need to be able to install a vehicle mounted CB set-up in your 4x4. If you have any questions or queries please just get in touch for individual advice.

Performance is dependent on many factors, but when fitted correctly, your CB set-up should give you a vehicle-to-vehicle range of up to 3-6 miles in open country, less in densely wooded or built-up areas, but considerably more from a high position. Obstacles in the way of the signal make all the difference on CB.

With nothing in the way, i.e. two vehicles on hills with nothing between them, some incredible distances can be achieved, 30-40 miles or more !

Below is our installation advice, but if you have not already read our Frequently Asked Questions, there is lots of other useful information there - please click here to read them

Before you start, you should decide on where you want to put the rig (CB unit) & aerial, and how you will route the cables between them. By the time you have finished reading this section, you should have a fair idea of where you will put everything, but if you’re unsure - give us a call.

If you order from us, we will make sure the aerial cable you buy is going to be long enough for your vehicle & chosen location, but you will need to make sure you have any other bits you might need, grommets, cable ties, insulation tape, and any tools required, i.e. drill, metal file and screwdriver.

If you buy a new set, it will come with approx 3’- 5’ of red & black 12v power cable, a bracket for mounting the rig, and a smaller bracket for the mic, along with suitable screws, washers etc.

I’ve always found it easiest to install a CB in the following order...

1 Install the rig in your chosen location, and check that it switches on.:
2 Fit the mount and aerial and run the cable to where your rig is located
3 Tune the aerial

You will need to put the rig somewhere where it will not get in your way. If you have the rig some distance from you, it may pay to use an extension lead for your microphone so that the lead is not tight across your steering wheel or selectors.

Depending on your choice of location for the set, you may find the internal speaker (on the underside of the unit) is obscured, or too far away to be heard in a noisy vehicle, so an extension speaker facing towards you, or behind your head is a definite advantage.

The rig will need connection to 12v power - if you have a 24v vehicle, you can use a 24v to 12v dropper. Many of these are enough to power a car stereo & other bits, so why not put in some extra power connections around the vehicle for other 12v items in the future?

If you will only be using the CB occasionally, and will be taking it in and out of the vehicle, and don’t want to fully install it, you can use the cigarette lighter socket (if you have one), but wiring direct to the battery is easy enough, and saves having wires dangling around.

(Pictured here is a Midland 48 Excel in a late model Range Rover Classic)

If you want to remove the CB when not being used, it is still worth properly installing it as you can quite easily remove the set from its bracket, and un-plug the aerial & power leads when you want to take it out, and from a safety point of view - it should be properly secured when off-roading. It’s tempting to jam it next to your seat with a jumper round it, or have it loose in a glove compartment or cubby box, but it’s a sharp metal box that you don’t want flying around, should something nasty happen!! It’s really not worth the risk.

Another advantage with wiring direct to the battery is that you will be less likely to get interference from the vehicles’ electrics, i.e ignition, alternator, fans, pumps, etc, although if you do suffer this, you may still need to use a filter to stop all ignition & alternator noise. (See our product pages for the interference filter and cigar lighter plugs & leads, connectors and extra power cable.)

When making the electrical connections, keep the rig switched off, or - even better - unplug the power lead from the CB (if you have a detachable type) until connection is complete.

(Pictured here is a Maycom EM27 in a much earlier Range Rover... mine!)

As a general rule, the higher up the aerial is mounted, the better it will work.

You should have the aerial in a position where there is nothing too close to it, as close proximity of other objects will have an effect on the SWR reading - more on SWR later.

Most mounts will require a hole to be drilled somewhere on the vehicle, although magnetic mounts will stick to steel roofs and bonnets.

With “through hole” mounting, you also have the advantages of having the connection & cables inside the vehicle, away from any branches that might snag, and avoiding the hassle of bringing the cable back into the passenger compartment.

If you decide to mount the aerial so the cable is outside the vehicle - use tie-wraps with short spacings to make sure you don’t rip the cable off with a passing branch. If you’re talking to someone very close, you might not immediately notice, but damage will be done to the set.

You have a number of places to fit an aerial on a 4x4 vehicle...

1 Through the roof : You can drill a hole in the roof to mount an aerial. Use a “dome” or “stud” mount for this. If fitting into a Land / Range Rover with an aluminium roof, care must be taken to make a good earth connection. You may need to add a strengthening plate for very large aerials.

(Pictured here is a full-size Springer on a dome mount on the roof of a Range Rover Classic)

2 Rear of the vehicle : This is often the best place to mount an aerial, as you can get the mount high up on the back of the vehicle, but with the aerial mount just below the roof line. This means the aerial will work well - being high, and give it some protection from branches.

Pictured here is a full-size Springer, mounted onto the back of a Land Rover 90, using a PSM-1 mount.

3 Roof rack : If you have a roof rack fitted, this can be a good place to have the aerial. Our mirror mounts will clamp around the bars of a roof rack - you will need to file a small area back to shiny metal (i.e past galvanised layer, or paint) to make a good earth connection. This doesn’t need to be a large area, just so that a part of the mount is making good metal-to-metal contact. The rack itself will act as a “ground plane” or earth - see below.

(Pictured here is a Sirio Hi-Power 4000 on a PL dome mount, bolted to a roofrack with a standard "mirror mount")

4 Rollcage : If you have a roll-cage fitted, this is another good place for an aerial - some already have lamp brackets on them, or if you can fabricate a small metal plate and weld it on or use exhaust clamps to secure it. Never try to drill through the rollcage to fit a mount - this will destroy it’s structural strength.

5 Front wing : You can put an aerial on the front wing, as long as it is not too close to the windscreen and rest of the body. At least 2 feet away is best. Again, a “dome” mount is ideal.

6 Gutter mount : Gutter mounts work well on steel roofed vehicles although they are on the side of the vehicle so they can be prone to damage from passing branches and their cables can easily get snagged on things. They are held on by two screws that tighten down into the trough of the gutter - they need to make metal-to-metal contact.

With aluminium vehicles you will need to protect this earth connection. The normal way to prevent alluminium from oxidsing is to use a zinc based paint like "Red Oxide" or similar rust inhibiting paints. Obviously, red paint on the outside of the car is less than ideal, so a spray-on (aerosol) plastic sealant will do the trick and not be so visible to the eye.

(Pictured here is a Sirio Hi-Power 4000 on a Sirio KF gutter mount)

7 Front bumper / bullbar : On the top of a bullbar is a common place for mounting an aerial - especially in Australia, in fact many ARB products have aerial mounting plates designed in. There is no longer a specific mount designed for bullbars, but I have seen exhaust clamps and plates put together to good use.

Do bear in mind that theft from this position might be a problem. Mounting on a standard bumper can work, although the amount of metal around the aerial can cause tuning and performance problems.

Also, having a flexible aerial down this low can be dangerous - getting whipped in the face is an off-road site marshals’ nightmare... and it has happened!

This is the most important part of installing a CB, and it's the bit that can have the most effect on how well your CB system works...

You need to use an SWR meter, an inexpensive and simple to use piece of kit - but please make sure you are familiar with how to use it... Click here to view our SWR meter users guide

The aerials we sell are the right length, this means that as long as your earth is good, and the actual aerial (in particular the coil) is not too close to any metal around it, you should get a reasonable SWR straight away.

You may need to adjust or cut the whip for the lowest reading.

If you do need to adjust the aerial, there is usually a grub screw to loosen at the top of the coil, to allow you to move the whip in and out . Where this is the case, you are acting on the wire “coiled” up inside the coil, so moving the whip in or out by half an inch may actually alter the length by several inches, so small adjustments are needed. It’s often easiest to cut the whip as you will normally need to make it shorter if anything.

Most aerials will tune in fairly well across 80 channels, but in order to get a very low SWR across all 80 you will need an aerial with a wide bandwidth - most of the Sirio range would be suitable. Aerials with wide bandwidths are usually very good performers although often more expensive than the more basic aerials.

You will probably find that most CB activity in this country, both off-road users and general users, will be on the UK band, so if you have problems SWR tuning over all 80 channels, try to get the best reading you can on the UK band.

This should ensure that at least the top channels of the EU band don’t have too high a reading. You may have to do this with small (3’ and under) aerials.

You may find that in some circumstances, often with aerials made in Europe, you will need to cut the whip. Do this with some caution. If possible try to find another piece of rigid wire that’s the same length as the whip of the aerial (fencing wire is ideal but a straightened coat-hanger or similar will often do the trick).

Use this as the whip and cut it down to size until you find the right length to give you a good reading, then cut the actual aerial down to this size and re-fit. This will prevent you cutting too much off the aerial by mistake, and the wire will probably be a lot easier to cut than the aerial’s steel whip, saving you time.

You may need to take anything from 1-5 inches off some aerials to obtain a very low SWR on the UK band.

Aerials made in Europe are tuned for the EU band and below, and we want to tune them for the EU band and above, hence why you often need to cut them. Luckily it’s this way around, as it’s much easier to cut a whip down than it is to add anything to it!

Making sure the aerial is correctly tuned is very important, as the power that does not get transmitted due to a bad SWR comes back down into your rig and can cause damage. Not only will this eventually lead to the death of your rig, but the performance of it while it does still work will be very much worse than if the SWR was good.

Although all new CB sets that we supply have a 12 month guarantee, this does not cover the output transistors, as they can be damaged by using an incorrectly tuned aerial. On older CB sets that have been around for years it is quite possible that the components are no longer available and if the set fails due to bad-SWR damage, the unit will be un-repairable.

If your SWR is very high, it's likely that your earth connection (groundplane) is not good - we have more information about groundplanes and curing earthing problems here. Following the advice in this section should mean that you have very few problems installing and tuning a CB set-up. However, if you do get stuck, just give us a call. For all the information we’ve tried to give here - there’s no substitute for individual advice when it comes to solving problems.