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Antenna Tips and Precautions
Download Video SWR instructions View with Windows media player or similar.
Download Antenna Stud Assembly Video View with Windows media player or similar.
Download Supply voltage troubleshooting Video View with Windows media player or similar.
We got about a hundred different antennas over here!!
That's an Antron 99 eighteen foot base station antenna hanging from the ceiling.
Brent has been with Truckcity since 1997.
Some people think CB antennas are ugly. That hurts. I don't like those big tall swingy around things but most of them are OK.
ANTENNA INSTALLATION TIPS, PRECAUTIONS AND ANTENNA LOCATIONS.
The best place to put a single antenna is smack dab in the center of the roof but very few people want it there. This is the highest place you can put it. This gets it up and out of the way of obstacles that could interfere with the radio waves coming out of the antenna. The sheetmetal (frame if there is no sheetmetal) of the vehicle is used as part of the antenna called the ground plane. Mounting the antenna in the center gives a balanced and uniform radiation pattern which will allow you to get out well in all directions.
The Antenna Mount
An antenna mount is a device that hooks your antenna onto your vehicle. Mounts are usually made of metal and have a plastic part which electrically insulates the whip from the metal. There are many kinds of mounts, almost as many as there are antennas. The most popular ones are the truck, hood lip mount and the mirror mount. The mirror mount is good for getting your antenna up high where it can get out (use twins on big rigs only because you must have the antennas 8 feet apart or your signal will go to the sides more than in front and behind). The trunk lip mount can also be used for mounting to the hood. An important thing to remember with any mount is that it must have a good electrical connection between the mount and the car body. Some mounts have an adjustable set screw which is tightened until the pointed end of the screw pokes through the body paint, electrically bonding the mount to the vehicle(use sealer a these points). Some other mounts require boring a hole through the body of your vehicle. Now don't cringe, for heaven's sake. Some times it works the best and it's the best looking too. The center conductor of the coax connects to the whip either directly, or through a loading coil. Neither the metal whip nor the center conductor can touch other metal (fiberglass antenna may touch but it does cause power loss). If you think that the whip might bend back and touch the metal body when your vehicle is in motion, you can insulate the section of the whip with some electrical tape or plastic tubing. If at all possible avoid installations where the antenna whip is up next to the vehicle's body. This is imperative for good performance. Any sheet metal, metal tubing, carrying racks or other antennas will absorb 25% or more of your power. If you test an installation next to something metal, you will almost always find a high SWR which cannot be tuned out. By all means, follow directions enclosed with the CB system you purchase. Most problems can be avoided by just reading the instructions before you begin. Special attention should be paid when drilling holes to make sure that the exact size drill bit is used. If the hole is too big the mount will loosen. I silicone the screws which locks them in and prevents corrosion, which is another one of CB signals enemies.
Hooking Up The Coax O.K.
We have gotten the radio wired up. Now we have to hook up that radio to an ear. In order for the radio signal to get from the CB to the antenna, you need some kind of wire to connect them together. Usually, a special kind of two conductor shielded wire is used, called coax. This special wire is made up of an inner wire covered with a plastic sheath, and outer wire mesh that in turn is covered by a black outer covering. Now there are several types of coax, but only two kinds are much good for CB-RG-58/AU and RG-8/AU coax (AU means stranded center wire which lasts twice as long as a single wire). Unless you're running 1000 watts in your mobile, RG-58/AU will work fine. RG-59/AU is sometimes used for twin CB antenna phasing harnesses elements. It should never be used for single antenna CB installations. It's good when installing a CB to get the coax up and out of the way, not only for looks, but also to keep it from getting stepped on or tripped over. Avoid flattening or crimping or wearing the insulation off. The coax will need to be connected to the back of the radio and to the antenna. This is done with a connector called a PL 259 that attaches to the coax. The coax and connector and everything else will be supplied when you buy a system from us. Connecting the Coax to the Antenna. Some antennas have the coax already attached. Other antennas either have a connector that plugs into the base of the antenna or the two terminals which attach to the antenna mount. It is important that the shield of the coax be securely connected to the body of your vehicle. The shield is the larger outside braided wire on the coaxial cable. Usually, the mount of the antenna provides this connection. If you are using a mirror mount type, make sure that your mirror braces are making good connections with the body of the vehicle. If any of the connections are not made properly, the antenna will not work right. Although you may be able to receive somewhat, you may not get out very well. Sometimes scraping down to bare metal is necessary in order to make a good connection (use sealer here).
SWR Download SWR meter instruction video
Is your Antenna Working Right? The length of your antenna makes a difference. Even though we can't see them, the radio waves SWR have an actual physical length. You must match your antenna's length to that of the CB radio wave. When your antenna is the wrong length, some of the power does not radiate, but is bounced back into the coax, and into the radio itself If this reflected power is too high, it can cause your CB's power transistors to overheat and even burn up! Besides, it's a waste of energy that should get out there and do its thing for you. So you want the least amount of reflected power and the most amount of forward power you can get. SWR means Standing Wave Ratio. Sounds rather high falootin', don't it? Well don't let it scare you off. It's simple. You can find if your antenna is the right length by using an SWR meter. Checking SWR First of all, you'll need a short coaxial cable with a connector on each end. Plug in one connector into your rig and the other into the socket on the meter labeled TXMTR or TX. Plug the coax that goes to your antenna into the socket on your meter labeled ANT. Turn the knob on the meter all the way down (counterclockwise). Put the switch in the forward or calibrate position. Turn on your radio to channel 1. It should be working normally. Press your mike button and, without saying anything into the mike, adjust the knob on the SWR meter until the meter reads set, or full scale. Then flip the switch to Reflected or SWR and read the SWR scale of your meter. After noting what the SWR is, stop transmitting. Then turn your radio to channel 40 and test. If the meter reads less than 1.5 on 1 and 40 your antenna is working properly. If it reads more than 2, your antenna probably needs some adjustment. If it reads more than 3 or in the red, check all connections at the antenna for possible bad connections; the antenna or the center wire of the coax might be touching the body of the vehicle. Coiling your excess coax into a small bundle can cause a high reading too. If this happens, the coax can be coiled into longer loops to avoid causing a high SWR. A poor ground connection here is a major cause of high SWR. If you obtain a high SWR when on a luggage-rack (which I've always found to work poor) mount it somewhere else. The same goes with mirror mounts (accept on semi trucks).. Antennas shorter than about .5 meters (1.5 feet) long will probably have a high SWR or not work quite as well on some channels than others. A short antenna will not tune a broad enough range of frequencies to include all forty channels.
Adjusting Your Antenna
So let's say that your SWR turns out to be 2: 1, and you want to bring it down. There are two ways to change an antenna's SWR: one is to lengthen it, and the other is to shorten it. You can figure out which way to go in the following manner: Take an SWR reading on channel 1, then take one on channel 40. Note which channel had the higher SWR? If the SWR is higher on channel 40, you need to shorten the tip. If the SWR was higher on channel 1, you need to lengthen the tip. Move it about 1/4" at a time or screw it out longer a turn or two at a time. Most antennas have a set screw you can loosen so that the tip can slide up and down. If this does not give enough adjustment, you can clip or file 1/4" at a time off the bottom of the tip and reinsert it in the coil. Make sure you put the cap(s) back on if the antenna came with one and to reset the SWR meter every time you take a reading. One little magic trick to impress your friends with is, if you bring your hand near the loading coil or the top of the antenna and the SWR goes down, the tip of the antenna needs to be lengthened; if the SWR goes up, the tip needs to be shortened (Because the capacitance to your finger electrically lengthens the antenna). If you're using twins, make equal adjustments to each side at the same time. If the SWR is in the red, do not hold the mike button in for more than 10 seconds at a time. This will protect the power transistors from possible burnout. When testing SWR on a system with a linear never go through the linear. Go from the radio to the meter and the meter to the antenna or you will get an erroneous reading and performance will suffer a lot.
OK, You have done everything according to the book and you still have a problem (your CB sounds like an old tin can). Bring it on down to Truckcity if possible and have us check it out and fix it for you. The smallest thing may be a may drain all your power because CB radios don't have much power in the first place. We should be able to help you get things squared away in a hurry. If you're too far away give us a call. 253-927-2088 Talk with Authority! Talk on a Truckcity CB and have a Great day!
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