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The G5RV antenna is a dipole with a symmetric resonant feeder line, which serves as impedance matcher for a 50 Ohm coax cable to the transceiver.
Contents
Origin
Louis Varney (G5RV) invented this antenna in 1946. It is very popular in the United States. The antenna can be erected as horizontal dipole, as sloper, or an inverted-V antenna. With an transmatch, it can operate on all HF amateur radio bands (3.5–30 MHz).
Impedance
While the widely used 50 Ohm coax cable is often used to directly feed this symmetric antenna, this is not good practice and should be avoided, since it can result in RF interference due to high current flow on the outer surface of the coax braid. A 1:1 current balun should be used between coax and ladder line. The balun not only prevents RF interference but reduces receive noise and increases performance
The dipole elements are 15.55 metres (51.0 ft) and the impedance-matching symmetric feedline (ladder-line or twin-lead) can be either 300 Ohm (8.84 metres or 29.0 feet) or 450 Ohm (10.36 metres or 34.0 feet). As is in general the case for all electric antennas, the height of the G5RV above the ground should be at least half of the longest wavelength to be used. The ends of the symmetric feedline are soldered directly onto a 50 Ohm coax cable (or the 1:1 balun) to the transceiver. A length of at least 20 metres (66 ft) of 50 Ohm cable is recommended. An antenna tuner is necessary for this antenna.
There are many variants of the G5RV antenna.