However, for most applications, the mobile antenna will use the vehicle's body as counterpoise. These no-ground-plane kits are generally marketed to owners of fiberglass vehicles. There is an exception to this general rule antenna systems that use the coax cable as a counterpoise.
Even if the manufacturer supplies you with an entire kit (coax, mount & antenna), this, in most cases, leaves you without the counterpoise requirement. The six needed components for a mobile installation are the radio, power feed, coaxial cable, antenna mount, antenna, and ground plane (counterpoise). Antenna manufacturers can supply you with an antenna that is pre-tuned to the general frequency of the intended equipment, but they cannot promise you perfect performance "out of the box". Unlike receive only antennas (AM/FM radio, TV, scanner), antennas that transmit require tuning. It could save you a lot of time, effort and possibly, money. Spend a few minutes to read this entire pamphlet and you will go into your project with valuable knowledge. You should strive to achieve a ratio below 2:1 on all channels.īefore measuring and setting SWR, it is helpful to know some of the things that can cause problems. Defective or inferior components, bad installations and antennas not tuned to the specific location on the vehicle increases the SWR. Generally speaking, the lower the ratio the better. It is a ratio of maximum voltage or current to minimum voltage or current. SWR (measured with an SWR meter) shows you how well your coax, antenna mount, ground plane and antenna match the output capability of your CB radio. SWR (standing wave ratio) is a term every CB'er should know.