1/26/2024 0 Comments Cb radio box 1.5To test for this, use a multimeter to check for continuity between the base of the antenna (the threaded part) and the very tip. If this wire is broken anywhere, you will get a high SWR. Many CB antennas consist of a copper wire wound around a fiberglass pole. We have a CB antenna installation guide that outlines choosing a location in more detail. To alleviate this, keep at least the top 12 inches of the antenna above the roof line, and position the antenna as high as possible on the vehicle. If your antenna is mounted down low on the vehicle, like on the bumper or behind a pickup truck's cab, the signal can bounce back to the antenna, causing a high SWR. ObstructionsĪnother problem occurs when obstructions prevent your antenna from radiating well. If you just don't have much metal on the vehicle, like with an RV or motorcycle, you may want to go with a no-ground plane (NGP) CB antenna. If you are mounting on a mirror or other bracket that extends out from the vehicle try moving the mount in closer. Make sure your antenna has as much metal under it as possible. You can read more on what a CB antenna ground plane is here. Insufficient Ground PlaneĬB antennas need a metal surface under them to transmit correctly. Good quality magnetic mount antennas shouldn't have a grounding problem. There really is no way to improve the ground on magnet mounts. For magnet mounts, the ground is formed through capacitive coupling with the metal of the vehicle (through the magnet). Running a grounding strap from the mount to the chassis can also work. If you don't have a good ground, scraping paint off where the mount contacts the vehicle can help (do this at your own risk). See our guide for testing a CB antenna ground for more information. You can test this with a light or multimeter just as you would test any vehicle ground. For metal mounts (mirror mounts, side mounts, 3 way mounts, etc) this is achieved through metal to metal contact. The mount your antenna is connected to needs to have a good ground to the vehicle chassis. Your standard CB antenna needs an adequate ground plane (a flat surface of metal at least 2 feet by 2 feet) and the antenna mount will need to be electrically grounded to the vehicle. Keep in mind that there is a difference between the ground plane and an electrical ground. If there is continuity, check the nylon washer placement on the stud. Use a multimeter to check for continuity between the antenna coupling nut and the mount. To test for an incorrectly installed stud remove the CB antenna and disconnect the coax from the stud. When the nut or bolt contact the mount, this fails. The whole purpose of an antenna stud is to isolate the antenna from ground. There are nylon washers that prevent this, but they are sometimes left out or installed improperly. Click here for information on testing CB Coax StudĪ short occurs in the antenna stud when the antenna coupling nut (where the antenna screws in), or the bolt, makes contact with the mount. If there is continuity, replace the cable. Use a multimeter to check for continuity between the center conductor and the shield. To test for this disconnect the coax from the CB radio and CB antenna mount. This can happen as a result of a defect from the factory, or a break in the cable. CoaxĪ short occurs in a CB Coax when the shield is making contact with the center conductor. There are two places a short can occur in a CB antenna system, in the coax and in the antenna stud. The most common cause of a high SWR is an antenna shorted to ground. Also make sure the doors and hood are closed on the vehicle. Make sure you are not too close to buildings, trees, other vehicles, etc. If you are not sure, check our guide describing how to tune your CB antenna. The first thing you need to make sure of is that you are taking SWR readings correctly. LocationĪnd by this, we mean where your vehicle is when you are taking readings. Improper storage of your coax (such as a circular style) could result in RF (radio frequency) issues that could interfere with your signal. Store any additional coax in a figure 8 style, about a foot in length, and loosely bound in the center with a zip tie. Verify that your coax is not crimped, bent, or crushed. Run the coax in a large figure 8 or purposely run the coax in a longer path to the radio. Coiling the coax up will cause the cable to mimic the coil in the antenna, creating signal feedback. Make sure that any slack you have in the CB coax is not coiled up. Often times, especially when you are using the factory recommended 18 feet of coax, you will have extra coax between the antenna and CB radio.
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