Frequently Asked Questions
Using the recommended length of 18' of coax cable can sometimes result in an excess amount of cable in the cab. This excess cable should be stuffed underneath the dash, under the carpet, or hidden by some other means. It should NOT be coiled into a neat roll or coil. This creates an "RF Choke" and de-tunes the antenna system, in some cases to the point of not being able to get the SWR down to an acceptable level.
That is almost an impossible question to answer with a specific distance in miles. The RF signal is affected by many influencing factors that have an effect upon the signal. These factors are: terrain - mountains, flat land, city buildings, time of day or night, height anld location of antenna, the sun spot cycle ( with its 11 year cycle - skip conditions ), frequency, and transmitter power. With so many variables, it is impossible to give a distance in miles. Generally speaking, you should expect a range of 3-5 miles, but it is not unusual to have results in the 5-20 mile range. Do not be surprised though if you are able to experience a range of hundreds of miles in ideal conditions. However, there are two factors that you can have direct control over: the transmitter power and the antenna. Staying within the legal limits of power leaves you with the antenna as your primary control over the distance. Therefore, you should pick the most efficient antenna that you can obtain.
Yes, with one caution: To prevent electrical degradation, make sure you do not use colors that have been loaded with zinc or other metallic particles used for coloration (lead-free paint). Dealerships, both automotive and parts stores, have paints made for painting plastic that also match the vehicle color.
For best appearance and finish that will most closely resemble the color of your vehicle, use a white antenna, as there will be minimum (if any) effect on the base color of the paint. Clean the antenna with denatured alcohol and let dry before applying paint. Follow directions of paint for drying instructions. When drying is complete, install antenna and re-check the SWR tuning.
NOTE: Painting the coil may have an effect on the antenna that could change the electrical length of the antenna.
If this occurs, both when the vehicle is in motion or stopped, it is an indication of a radio problem. If your transmitted signal is ok and understood by the receiving station, the same should hold true for your received signal. Re-check the transmitter, receiver or audio section of the radio, depending on the problem.
If the problem is only when moving, it may be a faulty connection, coax connector, or the antenna. See the Testing Antennas section to determine if the antenna is the problem.
This is definitely a radio problem. The CB antenna does not care if the signal, received or transmitted, is AM or SSB (or for amateurs - FM, or even CW). It cannot distinguish the difference between any of the modes of transmission. Again, you will need to check the transmitter section, receiver or audio section of the radio, depending on the type of problem.
This problem can be solved by one or more of the below solutions. The trouble is you never know which one will solve the problem in each given situation, and you may even need to use more than one solution to remove the problem completely.
Re-check your case ground on both your radio and the amplifier ( if amateur on 10 meters ) to verify that it is truly acting as a ground, and not radiating, acting like an RF choke or has become inductive. This will occur when a ground lead is so long that it acts like an antenna. The lead should be as short as possible, i.e. less than 1-2 ft.
If you are using an amplified microphone you may need to add a .001 µF bypass capacitor internally to the PTT line, and a .002 µF capacitor between the audio lead (of the microphone amplifier output) and the ground of the microphone.
Bond (connect) the radio to the amplifier (if used) with a good copper ground strap, keeping the leads as short as possible.
As a last resort, you may even need to use a 50 ohm line isolator between the radio and the amplifier, or between the radio and the antenna coax. The isolator will prevent RF from flowing back into the radio along the outer conductor of the coaxial cable.
When you can hear your CB transmissions through your auto radio, this is known as "feedback". The general cause is the coaxial cable is running across or next to the speaker wires from your AM/FM radio. Simply move them as far apart as possible or re-route the coax in a different manner.
Yes it can, but only with the use of the Wilson floating ground kit (see FGK). This special kit changes the antenna from a vertical type to a dipole type of antenna. It is very effective when installed properly, and will allow the antenna to tune down to a very low SWR. The key is to actually avoid the ground on the vehicle or boat and utilize a different type of ground. This is accomplished by installing a separate wire insulated from the vehicle ground. To start, insulate the bottom SO-239 portion of the mount from ground. Solder a large lug (with a 5/8 hole) on a well-insulated #10 or #12 gauge wire. The wire is then run into the cab of the RV or under the deck of a boat. Permanently secure with tie-wraps and/or silicon glue. (It is important that the wire does not move after tuning, or the SWR will change). After installation is complete, trim the ground wire for lowest SWR. CAUTION: High voltage can develop at the end of the wire. When tuning is completed, tape the end of the wire using black electrical tape. This is necessary as it is a voltage point for high power.
After you have verified that the antenna is properly grounded to the chassis or frame (not to the battery), the next step is to include an additional ground from the chassis of the radio to a good metal ground within the vehicle. (Note: This is not the power ground but a separate chassis ground). To do this, loosen a screw from the side or back of the radio, connect a wire to this point and re-tighten the screw. Attach the other end of the wire to a known good ground. If a power amplifier is used, it also should have a separate chassis ground wire as described above, installed. Remember to keep both the radio and the amplifier ground wires as short as possible.
Normally the best place to mount the antenna is on the center of the roof. However, due to the large ground plane area that is presented to the antenna on this type of vehicle, the center of the roof is not always the best place. Efficient operation is often achieved when the antenna is placed 6-12" from the front of the windshield. This especially holds true when the roof is equipped with a luggage rack. If the luggage rack is metal, keep the antenna as far away as possible to avoid de-tuning effects.
Yes it will. The general opinion is that mobile antennas mounted on vehicles are omni-directional. While true, it is not the complete answer. The actual radiation pattern (or direction of signal) is influenced greatly by the body of the vehicle. The radiation patterns shown below are a graphic depiction of the relative field strength transmitted from or received by the antenna.
In the drawings below, the lines show the typical radiation pattern you would realize from the antenna when mounted in three different positions of the vehicle. As you can see, the pattern varies from position to position and its shape depends on where you mount the antenna. This variation is the result of the amount or lack of metal around the base of the antenna. The pattern is pulled to areas where there is the most vehicle body. The pattern is the worst in directions where there is no or very little metal body to act as a radial. As you can see below, the best overall radiation pattern is achieved when you mount the antenna as close to the center of the vehicle as possible.
Yes you can. Sometimes because of the height of the whip, you may hit small or light overhead objects and feel that additional spring or give in the whip would give you more peace of mind. Purchase a small antenna spring, generally they are around 3" in length. You will probably have to re-drill (on the bottom) and tap the threads (on top & bottom of the spring) to 5/16 X 24. Remove the mast from the top of coil, screw on new spring and tighten. Then install the mast on top of the spring and insert the whip. You will have to re-tune the antenna, as this has added length to the antenna system.
Both an exploded view and an assembled view are shown below.
Sometimes at highway speeds of over 40-50 mph, you may hear a whistling sound coming from the antenna. This is caused by wind spillage over the hood and onto the roof. It does not affect the performance of the antenna. There are several ways to fix this problem.
1. A front hood bug shield can be added (or removed if one is installed).
2. Sometimes moving the antenna either more forward or towards the rear can cure the whistling sound.
3. Install a rubber type cover on the whip. Most often a length of very small diameter heat shrink tubing is placed over the steel whip, and using a heat gun, shrink the tubing to fit the whip.
Wilson's exclusive impedance matching transformer is connected through the external wire at the bottom of the FGT and Flex series of antennas. It is NOT a ground wire to increase the ground of the antenna, although using the lead does make the antenna DC ground. It is used when you are not able to get below a 2.0:1 SWR even after tuning. This generally indicates a mismatch of impedance between the coax and the antenna. This can be caused by poor ground but is generally attributed to the mounting location. It re-inserts 25 ohms impedance at the antenna feed point and brings the system back to the 50 ohms required. It is not a tunable device, therefore it is not fooling the radio into thinking the system is matched. It is actually matching the antenna and feed point to the required 50 ohms impedance for the coaxial cable. The most often time it will be used is when the antenna is mounted on the top of tool box in the bed of a pick-up, or on the passenger side of a tractor using co-phased antennas.
You have the choice of either cutting it off or taping it out of the way. In making your choice, consider if you may move the antenna to another vehicle, that installation might require the lead. For the most versatile use of the lead, simply lay it alongside the fiberglass and tape it in place. Using electrical tape will offer the easiest method and offer the best protection against weathering conditions.
Removing the top plastic cap reveals the tuning tip of the antenna. Simply loosen the set screws and slide the tip up or down for best SWR. Remember: It is necessary to have the cap on the antenna when testing for SWR and while in use. There may be some installations that the whip supplied is too long, even when fully inserted into the top. If, even after removing tip, the SWR is still too high, you can grind a little off the top of the brass top. In other installations, the tip may not be long enough. When this is the case, you can make your own by using a length of stiff wire or welding rod. If it is necessary to have a whip tip longer than the cap will allow, simply punch a small hole in the top of the plastic cap, extend the tip through the hole and tune the antenna. After tuning, seal the hole with some type of sealant, such as silicon seal, to prevent moisture from getting into the antenna.
Because Fiberglass antennas are top loaded, performance is improved when a minimum of 2/3rds of the total antenna height is above the roof top. In installations where this is not practical, use the one that will permit all of the top loaded portion to be above the roof.
If you are using less than 1000 watts, and a single antenna, use an 18' length of RG-58/AU. This cable is 95% shielded, stranded center, with 50 ohms impedance. If your power is less than 2000 watts, then change to the RG-8X type (also called Mini-8 or Super 8). For co-phased antennas with less than 1000 watts, use RG-59/AU. For power less than 2000 watts, use RG-11/AU. Both co-phasing cables should be 18' in length on each side. Wilson has available a high quality line of coax cable, and may be viewed at: Coaxial Cable.
Using the recommended length of 18' of coax cable can sometimes result in an excess amount of cable in the cab. This excess cable should be stuffed underneath the dash, under the carpet, or use some other means of hiding it. It should NOT be coiled into a neat roll or coil. This creates an RF Choke and de-tunes the antenna system, in some cases to the point of not being able to get the SWR down to an acceptable level.
The optimum distance for co-phased antennas is 8 ½ to 9 foot between the antennas. This produces greater signal forward and backward on the vehicle, which is generally the desired pattern. If the distance is less, the pattern will change. A good "rule of thumb" is: 7' - 9' = front to back radiation strongest, 6' - 7' = side to side radiation strongest, generally a 5' separation will produce no difference in pattern radiation than a single antenna, and antennas installed with a distance of 4 ½ foot or less, tend to fight each other and would result in less performance than with a single antenna.
When a reading of 3.0:1 is present on all channels, this indicates a lack of ground for the antenna. For example, a lot of the tractors and RV's today are made of fiberglass or similar material that offers no ground to the antenna. Others may have only fiberglass doors, or may be on an air ride cab. Either situation insulates the mirror from the actual chassis or frame ground. To eliminate this condition, a jumper wire must be installed from the antenna mount to the frame or chassis ground. There is a specific method to properly accomplish this grounding. Note that the wire lengths should be as short as possible, not to exceed 3' in length of any one piece of wire.
- Begin by running a length of stranded 10 or 12 gauge wire from a bolt on the antenna mount to the bolt holding the mirror to the door.
- Install a separate wire from this bolt to a bolt on the top door hinge.
- Run another wire from the top door hinge bolt to a bolt on the bottom door hinge. (If the door frame is steel, this wire may not be required).
- Install the last link to ground by running a wire from the bottom door hinge bolt to the chassis frame.
- This completes the ground installation, and the antenna may now be tuned in the normal manner.
NOTE 1: Do not run a 1-piece length of wire from the mirror mount to the frame. This causes the antenna to see an unbalanced condition, with the ground wire trying to radiate, making proper tuning impossible.
NOTE 2: Other notes and solutions to this problem can be found at Trucker Notes, item 15.
Yes, you can, but special items must be taken into consideration. Grounding, the right type and kind, is the biggest. One of the easiest and simple for all around use is by making a dipole setup. Two methods are described at the following page: Dipole
Yes, but it will require some special whip lengths. See FGT on Ham Bands for additional information.