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. 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. It can operate on all amateur radio bands within 3.5 through 30 MHz. 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 as 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 of course increases performance 
The dipole elements are 15.55 metres (51.0 ft) and the impedance-matching symmetric feedline (ladder-line) can be either 300 ohm (8.84 metres or 29.0 feet) or 450 ohm (10.36 metres or 34.0 feet). As for all antennas in general the height of the G5RV above the ground shall be at least half of the longest wavelength to be used. The ends of the symmetric feedline are directly soldered to a 50-Ohm coax cable to the transceiver. A length of at least 20 metres (66 ft) 50 Ohm cable is recommended. An antenna tuner is necessary for this antenna.
There are many variants of the G5RV antenna.
- HF Antennas for all locations (L. Moxon, G6XN)
- G5RV multi-band antenna (Louis Varney, G5RV) http://www.astrosurf.com/luxorion/qsl-g5rv.htm
- The G5RV Multiband Antenna ... Up-to-Date (L. Varney, G5RV in The ARRL Antenna Compendium Vol. 1)
- Practical Wire Antennas - Effective HF Designs for the Radio Amateur (J. Heys, G3BDQ)
- ARRL Antenna Book 21st Edition – Chapter 7
- Novice Antenna Notbook (D. DeMaw, W1FB)
- Rund um die Antenne (M. Rüegger, HB9ACC) http://www.wreiner.at/2008/05/24/rund-um-die-antenne-von-hb9acc/
- Maxwell, W. (2010). Reflections III Transmission Lines & Antennas
- What I learned from building my own G5RV / ZS6BKW Antenna (VK4MDX) http://vk4mdx.wordpress.com/2009/02/15/what-i-learned-from-building-my-own-g5rv-zs6bkw-antenna-part-1/
- Practical Antenna Handbook (4th Edition, J. Carr)
- HF Antenna Systems: The Easy Way (J. M. Haerle)
- The ZS6BKW Multiband HF Antenna Revisited (M. Vincent, G3UKV) http://www.ab4oj.com/dl/sprat_zs6bkw.pdf
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