A digital or analog antenna meter is sometimes known as a standing wave ratio (SWR) meter. This handheld or mountable signal meter aids in tuning an antenna. An antenna doesn't transmit its electromagnetic (EM) radiation equally in every direction; it must be adjusted for optimal performance. This measurable magnitude pattern is known as its field strength, or received signal level.
When arranging an antenna for a Citizens Band radio or other transceiver, it's important to gauge how much signal is transmitted and received. An antenna meter detects and gauges a ratio of maximum amplitude of a standing wave to minimum amplitude. It may be a needle that indicates reception, perhaps as a percentage of total output power. This can help people evaluate where to mount antennas, and how much antenna they need.
These meters can minimize difficulties and interferences caused by improper positioning and mismatched power use. Rural areas may have no telecommunications systems; urban areas suffer interferences from materials and structures. A properly designed CB antenna system can provide a reliable method of communication for remote or mobile positions.
Some users attempt to increase power to their radios via amplifiers, boosting signals perhaps beyond legal limits. A relatively cheap SWR meter and decent antenna provide a useful alternative to an amplifier. With an amp, interferences caused by poor antenna positioning may still exist, while increased power transmissions spill over into other bands and devices.
An antenna meter allows measurement of tuning ranges in frequency megahertz (MHz). With it, users can adjust many varieties of antennas, such as monopoles, dipoles, and Yagis. The device aids in the measurements of resonant frequencies and bandwidths of EM waves.
Such devices also permit unpowered adjustments of radio frequency (RF) matching networks and amplifiers. They can determine impedances or signal losses. Meters can also be used on transmission lines, coax cables, and stubs.
The measurement, technically a ratio of voltage to distance, is expressed as decibels (dB) per millivolts per meter (dBmV/m) in high-powered telecommunications transmissions. In low-power personal transmissions, it's measured as decibels per microvolts per meter (dBµV/m) or decibels referenced to one milliwatt (dBm).
Typical antenna meter units may have controls for calibration, field strength, forward power to the antenna, and reflected power from the antenna. The idea is to reduce back reflected signal and keep it under a red zone on a scale. Other scales might indicate reflected power and peak envelope power. The device is sometimes connected by a patch or lead between a transceiver and antenna.
Antenna meter devices can reveal optimal tuning, antenna length, and grounding. Placements affect the system's capability. An antenna meter can better locate positions, elevations, or groupings, and correct for EM field distortions, as around a vehicle.