is the maximum allowable VSWR?
VSWR (voltage-standing-wave-ratio) represents the degree
with which an antenna is "matched" to the system impedance.
Most modern antennas do not require any tuning for optimum performance.
VSWR is one of the easiest parameters to measure and VSWR meters
are becoming very popular antenna installation tools.
Most modern antennas, receivers and transmitters are designed
for peak performance when operating into a 50 Ohm transmission
line. If the VSWR is too high, the transmitter power may be reduced
as well as the strength of the received signal.
The typical commercial standard for maximum allowable VSWR across
the entire bandwidth of a system is 1.5:1. This means that the
antenna impedance must be somewhere between 37.5 and 75 Ohms.
You should specify the maximum VSWR and the operating frequency
bandwidth when specifying your antenna. A VSWR of 2:1 or greater
usually is considered unacceptable (or for receiving purposes
only) since it increases losses in the transmission line. Incidentally,
decreasing the VSWR below 1.5:1 will often be expensive and will
have little noticeable performance improvement.
Technologies, Inc. and the author retain the rights to all intellectual
This information should be used as a guideline
only to help you in the appropriate selection of an antenna.