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Two-way traffic!

Magazine Clipping Article; How to Install a CB 'rig'

CB Radio Fitting

It's essential to use an SWR meter (on right of picture) for setting up your CB & Aerial</b></p>
	<p ALIGN=In Part I of this guide (see LRO April 2002, pages 58-59), we highlighted the best buys in CB radios and explained why CB is best form of transmission for greenlaning.

Unlike Personal Mobile Radio (PMR) two-way radio, which by law cannot use an external aerial, most CB rigs are actually designed for connection to a vehicle aerial -even hand-held rigs can be connected to them. This means that the CB can be used inside the metal body of your Land Rover without loss of signal strength.

And there's no need to start drilling holes in your Land Rover to mount the aerial, though this is the most common method. Nor do CB aerials need to be ridiculously long or ugly, they can be no more obtrusive than a conventional radio antenna and they're simple and cheap to install.

What type of aerial?

Springer-type aerials, like this one, are a popular choice for off-roaders. They're durable, effective, and cheapDespite their length, springers are flexible enough to deal with overhead foliage

Before deciding which aerial to buy, you need to think what you're going to use CB for. Put simply, the longer the aerial, the better it will ultimately perform. So if you're planning to just use CB for greenlaning where all other vehicles are close by, a short rubber aerial is more than adequate.

If you're using CB to communicate with other road users over increased distances, say for traffic reports, then a longer one is a better bet.

 The next decision is whether to go for a rigid, or flexible aerial. Sprung-type aerial mounts allow rigid antennas to bend round obstructions, but they are still not the best choice off-road.

A dome mount is bolted through the panel and connected on the underside, keeping cables inside the vehicleMany road-use aerials use a coil of wire wound around the outside of the antennae, which is susceptible to being hit. If it gets damaged and the wire is broken, the aerial is useless.

an electronic ground plane (shown here with aerial attached) eliminates the need for a conventional earth connectionOne of the most popular off-road choices is the Springer, which gets its name from a coil spring on the bottom. These are completely flexible, almost impossible to wreck, cost little more than a tenner, yet are long enough for good performance.

Some keen CB users have two aerials; a rigid one for optimum on-road use, and a short 15-inch 'Rubber Duck' for off-roading. Swapping them is easy, as most aerials have a standard 3/8-inch UNF thread on their base, which screws into practically all mounts. If that seems longwinded, you can even get some quick-release bayonet fittings for the cable.

Mounting your aerial

Generally, you should put the aerial as high up on the bodywork as possible for best results. But that increases the risk of damage from trees, especially in the case of a long rigid type during off-roading. On hardtop Land Rovers, a good position is on the rear panel, just below the roofline.

Magnetic mounts provide great performance with no paint damage or permanent fixingImported US rubber aerials, available from Communication Eleven, are ideal off-roadDon't want to drill a panel to mount your CB aerial? Then use a gutter mount to secure it to your vehicle

Next choice is what aerial mount to use. The most temporary types have magnetic mounts. They make a good earth through magnetism and don't require any paint to be scraped away.

Roof Rack mounts are a good alternative to gutter mountsThey come with a large rubber boot to avoid paintwork damage. But, of course, a magnet won't stick to aluminium Land Rover panels. One way round this problem, if you can get to the underside of the panel, is to use a complimentary magnet to attract and hold the one on top in position.

For a more permanent solution there are a variety of different mounts that fit through holes in panels, on bullbars, roof racks, and even on roof gutters.

Bear in mind they must have a good earth connection, which usually means scraping paint away or running an earth lead down to a suitable earthing point elsewhere on the vehicle.

an electronic ground plane (shown here with aerial attached) eliminates the need for a conventional earth connectionAgain, aluminium has its own problems here because it oxidises when exposed to the atmosphere. So paint over the connection between the panel and the earthing point on the mount with red oxide paint, or spray electrical sealer on afterwards to slow the process down.putting sealer spray around the mount slows down the problem of oxidisation and helps maintain earth (or ground)

Another solution is to use an Electronic Ground Plane. This electronic aerial mount does away with the need for the aerial to be earthed to the vehicle, so you can mount it anywhere and to any panel material without damaging your paintwork.

 

Positioning your rig

There are few hard and fast rules about where the rig is positioned, but always remember that it should be securely fastened down. Ultimately, this tough and rather heavy unit could cause a nasty injury if it flew across the cabin in an accident. Obviously you should have the microphone close to hand and the rig needs to be visible and reachable.

Mounting a rig on the dashboard is ideal for sound and accessibility, but security may be a problemOne factor to consider here is how many controls the microphone has on it. On some models practically everything's on there, so it doesn't matter if the rig's fairly inaccessible. Also check the rig's audible volume when installed in the vehicle. If it's quiet, either have it as close to the driver as possible or invest in extra speakers.

Once you've chosen a site for your rig, you need to consider where to power it from. Some units come with a cigarette lighter plug for power, though they can be permanently wired, too. According to our expert, wiring direct to the battery minimises the risk of electrical interference, and it's simpler. If there s still interference, use an inline noise filter or replace the power lead with CB co-axial cable, which properly shields the supply against interference.

Finally, before using the CB for any time, do a Standing Wave Ratio (SWR) check on the aerial using an SWR meter which costs from under 10 and comes with full instructions. This shows how much power is being reflected back into the set from the aerial - a low reading means most of the power is being transmitted, as it should be.

High SWR may be due to incorrect aerial length or a poor earth. If you find that the SWR is high then your transmission range will be reduced, and you could wreck the rig too.

You're almost there

Before using your CB, call the Radio Licensing Agency (tel: 0117 9258333) and get an application form for your CB licence. This costs 15 a year, and is free for under 21s. While many CB users don't bother with it, the fact remains that it's the only certain way the Radiocommunications Agency can monitor CB usage. If they suspect the system is hardly used, they could all too easily pull the plug.
 

WE WOULD LIKE TO THANK...

Range Rover owner and CB specialist, Jim Aitken is the ideal contact for off-road communicationsJim Aitken of Communication Eleven (tel: 01737 245840), for his help with this feature. Jim founded Communication Eleven six years ago and reckons that it's still the only firm to specialise in CB for 4x4s.
As well as stocking all the CBs that were shown in our earlier test, he also supplies all the mounts, aerials, and accessories you could need for setting up a CB system. Call Communication Eleven for a 4x4 CB Radio catalogue, which also contains loads of buying, installation and general advice on all matters CB, including a CB beginners1 section.

 

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