Oct 10/98 - After reading numerous CB radio discussions on the Toyota 4x4 Mailing List, I have written the following article in non-technical terms in the hope of assisting those with questions about CB radios. I have worked in the radio-communications industry in the past, both managing the two-way radio division of a communications company, and selling and installing commercial two-way radio equipment. As a hobbiest, I am an Advanced-class amateur radio operator. I don't pretend to know everything, and some people may disagree with some of my ideas, but this is based on my own experience.

A CB radio is an essential piece of equipment for a 4wd. It can be used to disseminate time-sensitive information to multiple trucks while enroute to a destination, it can be used for trail recon purposes, and it can be used to keep everyone in touch while they are spread out over several km's on a dusty road.

Mobile radios can be purchased for as little as $50 or less, and fancier radios can exceed $500. Hand-held CB's are also available; they are useful for short distances only, and usually lack some of the desirable features of their higher-powered brothers. You can expect to pay between $150-$250 for a decent mobile CB (all prices are $Cdn). Desirable features include:

RF Gain - allows you to adjust the sensitivity of your receiver. This is useful when the vehicles you are communicating with are in very close proximity; turning the sensitivity down will eliminate the distortion that occurs when their radios overload your receiver.

NB or ANL - noise blanker or automatic noise limiter. Helps to reduce ignition and atmospheric noise, and is usually left in the "on" position.

The radios that I personally like the best are made by Uniden, which include Uniden, Cobra, President, some Realistic (RadioShack), and numerous other off-brands. The decent models have excellent filtering and a nice audio section. Current models that I recommend are the Cobra 148GTL (aka President Grant) AM/SSB mobile, and the Cobra 29LTD Classic AM-only mobile. Some models have "VHF weather radio receive"; however, the sensitivity of a CB on VHF frequencies with a CB antenna is not all that great, so I don't recommend paying extra for this feature if you have a choice. Also, while a fancy "SSB" (single-side-band) radio is nice, most 'wheelers have AM-only radios; if the main purpose of purchasing a CB is to talk to them, then save your money and buy an AM-only radio. If everyone in your group has SSB, then you can switch over and enjoy the increased range and quieter operation that SSB offers.

There are many small-sized CBs on the market; while they fit nicely into tight spaces, they generally have less filtering (against ignition noise, atmospheric noise, and adjacent channel interference) than the larger units. As well, these smaller radios rarely put out the full legal 4w RF output power, and are usually set somewhere between 3w and 3.5w. Finally, most smaller radios use a smaller speaker due to the case size, making the received audio sound a bit tinny; this can be improved with the use of an external speaker (4" diameter type).

Some CBs use LCDs (liquid crystal displays) instead of LEDs (light emitting diodes) to display the channel number; I prefer LEDs to LCDs as I have had LCDs freeze up in cold weather.

A good deal can sometimes be found on used radios, although the usual caveats apply. Models to watch for include the Cobra 138XLR, President Grant (old board), Realistic TRC-449, TRC-450, TRC-451, and pretty much any 28-series and 29-series Cobra radios. Beware of buying a used radio from an unqualified individual who thinks he's a CB technician; these radios are frequently "screwdrivered" in an attempt to gain increased power, which frequently results in detuning the radio.

In some countries, "export CB's" are available; these have added features such as as FM, more channels, higher power, etc. Many of these radios are marketed as 10-meter ham radios, easily modified for CB. Some models include Cobra 148GTL-DX, RCI-2950, President Lincoln, President Jackson, Uniden HR-2510, and others sold under the "Galaxy" and "Superstar" brand names. Almost all of these radios are manufactured by Uniden, and are the same size as the Cobra 148GTL.

You will also require an antenna; there are three popular styles; the 102" whip, the fibreglass antenna, and the base-loaded antenna.

The most efficient antenna is the 102" whip (1/4 wave); however its long length makes it impractical for many trails. Two models are available; a steel whip and a fibreglass whip. If you are going to the 102" whip, get the steel version; the fibreglass version will crack after repeatedly slamming into overhead branches. This may not be an issue in some areas, such as sand dunes.

I do not recommend the fibreglass antennas such as the Firestik or any of its clones; the fibreglass will eventually crack from the impacts with branches, and the longer antennas are quite heavy and will flex the sheetmetal where it is mounted. They are also not as flexible as the tapered-steel whips found on the base-loaded antennas.

The base-loaded antenna is my recommendation; most function as a loaded 1/4-wave antenna, with a "loading coil" in the base making up for the shorter physical length. Reputable brands include Larsen, Sinclabs, Wilson, K40, and Antenna Specialists. For off-road use, you should make sure your antenna has a "shock spring" to allow the antenna to flex easier when branches are being dragged over it; until I added a spring, my Larsen whip would end up bent back into a near-horizontal position after a day on an overgrown trail. Expect to pay around $100 for a good antenna, with coax, connector, and mounting bracket.

I do not recommend installing "dual" antennas; the two antennas are difficult to tune properly, and they require a special coax harness for optimum efficiency (50-ohm impedance from the radio to the "Y", and 100-ohm impedance from the "Y" to each antenna; most manufacturers use readily-available 75-ohm coax instead of 100-ohm coax, which is a compromise at best). At CB frequencies, this setup requires the antennas to be located 102" apart.

Do not ever buy a "cheapie" antenna, such as the two-foot-long type with a magnetic base, really thin coax, and loading coil around the middle of the whip. These antennas will get destroyed off road, and are very inefficient (ie. short range). In fact, "mag-mount" antennas do not provide a good electrical connection to the ground plane, and are not as efficient as a properly-mounted and grounded antenna. Also, never buy one of those "cellular look-alike" CB antennas; they are worthless. One thing I can't understand is why some people spend huge amounts of time and money on things like suspensions, lockers, trick armour, and other mods, and then go "cheap" on their communications gear. What do you use more, your CB or your winch? Spend some cash on good equipment, install it properly, and you will have a reliable, trouble-free setup that will be working when you need it.

The antenna cable ("coax") should have a 50-ohm impedance; the most common type for mobile installations is RG-58/U. For our purposes, coax length is not important for a properly-tuned system; coax signal loss is expressed in dB/foot, so shorter is better. Buy good-quality coax, paying special attention to the braid (shielding). A nice tight braid is desirable (less loss), as is a stranded center-conductor (withstands flexing and vibration better). Avoid coax with a foam dielectric (the insulating layer between the center-conductor and the shield); a teflon dielectric is best. Reputable manufacturers include Amphenol, Belden, and Larsen. Only use solder-type coax connectors, not crimp-type connectors. This is just common sense when you consider the amount of vibration the system is subjected to in our vehicles. Cut off excess cable; do not bundle or loop the coax up and stuff it under the carpet, as this will cause an inductance, which will affect the efficiency of the system. If you are purchasing your antenna system in components, buy a good-quality coax connector such as the units made by Amphenol. I have found that "cheap" connectors are difficult to thread onto a radio while you are out on a trail, in the dark, and in a hurry. You do not need to buy the "silver plated" or "teflon dielectric" connectors; these features are not relevant on CB frequencies.

Your antenna has to be "matched" to your radio. This requires an "SWR meter" and usually involves cutting the whip to a specific length or adjusting the whip position relative to the coil with a set-screw; higher frequencies (ie. Ch-40) require a shorter antenna, and lower frequencies (ie. Ch-1) require a longer antenna. Usually, the antenna is tuned to middle of the band; in our case this is Ch-19 (27.185 MHz), due to the way that CB frequencies have been assigned. Do not rely on a manufacturer-supplied "cutting chart" for your whip length; these charts assume your antenna has a perfect "ground plane" (radiating surface) and that there are no nearby metallic objects such as your roof and pillars. If you are installing the antenna on the fender or cowl, make sure that your hood is closed and that nobody is standing close by while you are checking the match. Do NOT attempt to match the antenna if you are not qualified; get someone who knows what they are doing to do it for you. If you do not match the antenna to the radio, you run the risk of some of the outgoing RF energy being reflected back into your radio; this can result in blown "finals" (RF output transistors). A properly-matched antenna will give you the maximum range, both transmitting and receiving. An SWR reading of 1.5:1 or less is generally considered to be acceptable (updated: see below for instructions on matching).

In an ideal world, the antenna should be mounted in the center of the roof. Several factors generally prevent us from doing this, the most common being our unwillingness to drill a hole in the center of the roof. In addition, a high-mounted antenna will be subjected to a lot of abuse from overhanging branches, flexing the roof sheetmetal, which has been known to crack paint and cause rust. Practically, the best place for a base-loaded antenna is on one of the front fenders via an L-bracket, midway between the nose and the A-pillar. This provides a nice balance between aesthetics and electrical efficiency. The centrally-located position provides a (limited) ground plane in most directions; mounting the antenna too far forward will send the signal towards the back of the vehicle (the area with the most metal), while mounting it too close to the A-pillar and roof will adversely affect the match and will block the radio signal somewhat. Mounting an antenna on a bumper will put it close to the side of the body, which again will affect the match and will block the radio signal. Obviously, the type of vehicle you own and the type of antenna you have will dictate where you can mount the antenna.

When you are installing the CB power cable, it is best to take the power right from the battery. This will help reduce the amount of ignition noise, and allows the CB to be powered up even if the ignition switch is jammed in the "off" position. There should be a fuse located as close to the battery as possible; most cables have an in-line fuse located close to the radio, which will protect the radio but will not prevent a short (and subsequent fire) when something abrades the cable between the fuse and the battery. Common-sense note: carry a couple of spare fuses for your CB; they are usually rated between 3 and 5 amps. The "ground" (black) side of the cable does not need to be run right to the battery; it can be attached to a bolt that threads into the firewall or the metal behind the kick-panel. There is usually an existing factory ground location that you can use. However, you may experience ignition or engine noise if you do not run the ground wire right to the battery or to the grounding location near the battery. I use crimp-type ring connectors ("blue insulator" size), but I remove the blue plastic insulator, slip a piece of rubber heat-shrink tubing over the wire, crimp the connector on for strength, and solder the wire to the connector for reliability. I then slide the heat shrink tubing up over the connection and shrink it to fit; this makes for a neat, professional appearance. If you are buying or building a power cable, the heavier the wire gauge, the better. A heavier-gauge cable can handle more current, and has the added bonus of reducing ignition noise. Make sure the cable is routed such that it does not interfere with the operation of the pedals, e-brake, or anything else under the dashboard.

When mounting the CB radio, ensure that the microphone cable does not interfere with the e-brake handle, shifter, etc. Mount the unit such that it does not interfere with air-bag deployment or seat movement. Mount the radio solidly onto metal; repeated jarring will tear the radio loose from anything else. Take your time and consider all the options before you commit yourself to drilling holes. Ideally, mounting the radio as high as practically possible will still allow you to call for help when you have water flowing through your truck (unless you're upside down in a creek, but then you have more important things to worry about). When checking for available space, remember that you need to allow room to clear the power connector and coax connector and coax. An "elbow" adapter for your coax can give you a bit more clearance in an in-dash installation; the signal loss with this additional adapter in line is negligible. Amphenol makes a decent adapter.

Update: Matching Antennas

Several people have asked how to match an antenna, so I've added it. I recently gave similar instructions to a friend over the phone, and he was able to match his antenna with no problem whatsoever. The usual disclaimers apply; don't attempt it if you aren't totally confident you can do it, and I am not responsible for any damages that might occur.

You will need an "SWR meter" and a short coax patch cable. The patch cable should be as short as possible, ie. 1 or 2 feet. You will also need to access the antenna connector on the back of the CB, so do this BEFORE you permanently install the CB into your dashboard.

Typical SWR meters generally have the following controls: a knob labelled "tune" (or "adjust"), and a switch labelled "forward" and "reflected". There also may be a switch marked "power" with the settings "5w" and "100w" or similar, corresponding to the power scales on the meter. On the actual meter face, there should be a scale with readings similar to "1.0, 1.2, 1.5, 3.0, and then a "red" reading up to the far right-hand side which should be marked "set" or "tune". This scale will tell us the "match", and is a ratio to 1, ie. 1.5:1.

Attach the SWR meter to the CB via the patch cable, and attach the antenna to the SWR meter. The two connectors on the meter will be marked "radio" (or "input") and "antenna" (or "output"). Turn your CB on, and set it to Ch-19 (the middle of the CB band). Set the SWR meter to "forward" and to "5w". Turn the "tune" knob fully counterclockwise.

Press the push-to-talk (PTT, or "transmit") switch on the microphone. While the PTT is pressed, slowly rotate the "tune" knob clockwise until the needle is at the "set" mark on the scale. Switch the meter to "reflected". This reading is the current "match" of the antenna to the radio at the middle of the CB band; a reading of 1.5:1 or lower is good. Write it down. Release the PTT.

Change your CB to Ch-1. Take another meter reading (turn the "tune" knob fully counterclockwise, switch the meter to "forward", press the PTT, rotate the "tune" knob to "set", switch the meter to "reflected"). Write down the value.

Change your CB to Ch-40. Take another meter reading, and write down the value.

Compare the values you have written down. If all of the values are 1.5:1 or lower, then I'd advise leaving it alone, as any further tuning will not give you any noticeable performance gain. However, if any of the values are higher than 1.5:1, your system will benefit from properly matching the antenna.

If the match is better (lower) on Ch-1 than Ch-40, then the antenna is too long. If the match is better on Ch-40 than Ch-1, then the antenna is too short. If the match is best at or near Ch-19, and gets worse at both Ch-1 and Ch-40, then it is already optimally tuned.

If you have a base-loaded antenna, ie. an antenna with a coil at the base, you can usually adjust the antenna length by loosening the hex (Allen) set-screw in the cone at the bottom of the whip, and moving the whip up or down by a quarter of an inch. Don't cut more than 1/4" off at a time; better to be too long and make several cuts than be too short and have to buy another whip. Also re-read the notes in the main text about matching antennas. Each time you adjust the antenna, check the match on Ch-1, Ch-19, and Ch-40.

If you have a fibreglass (top-loaded) antenna like a Firestick or Skipshooter, there is usually a rod at the tip of the antenna that can be adjusted up and down by loosening off a hex set-screw then re-tightening it. Sometimes this rod is hidden by a plastic end-cap that is slid over the tip of the antenna. Other fibreglass antennas require you to actually pull off some of the coil windings to adjust the match. To make the antenna shorter, you can pull up a winding (or portion of winding), and cut it off. To make the antenna longer, you can pull (slide) one or more windings up towards the tip, separating them from the main body of windings.

If you add a shock spring to your base-loaded or fibreglass antenna, you will have to shorten the antenna by the same amount as the length of the spring (the physical length, NOT the unwound length!).

You do not usually have to tune a 102" whip. Note that these whips come with a spring; if you do not use the spring then the antenna will be too short.

Dual antennas are a pain in the butt to match, and are not covered here (sorry), although the basic principles remain the same. Remember that the SWR reading is affected by BOTH antennas.

If you are wondering what "SWR" stands for, it's "Standing Wave Ratio".

Tips

If you are receiving ignition noise, you might try switching to "resistor" spark plugs and wires, making sure the "positive" power wire is connected directly to the battery, relocating the "ground" wire, using heavier gauge power cables, or installing a noise filter (rarely effective unless you are prepared to spend lots of money on a quality filter).

Use plain language, not 10-codes or "CB lingo". CB lingo went out when the movie industry stopped making "Smokey and the Bandit" sequels. Plain language allows everyone to understand the message, and helps to avoid misunderstandings, especially during emergencies.

In BC, most 'wheelers use Ch-4. This allows us to hear other 'wheelers who may be on the trail in the area, and gives us a common channel to holler for help when we are stuck or injured.

Hopefully this will have been of use to somebody.

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