G5RV antenna

The G5RV antenna is a dipole with a symmetric resonant[1] feeder line, which serves as impedance matcher for a 50 ohm coax cable to the transceiver.[2][3]

G5RV Antenna

Origin

Louis Varney (G5RV) invented this antenna in 1946.[4] It is very popular in the United States.[5] The antenna can be erected as horizontal dipole, as sloper, or an inverted-V antenna. With a transmatch, it can operate on all HF amateur radio bands (3.5–30 MHz).[5][6]

Impedance

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).[7] 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.[1]

The ends of the symmetric feedline can be soldered directly onto a 50 ohm coax cable (or a 1:1 balun) to the transceiver,[2] however this is not good practice and should be avoided: It can result in high current flow on the outer surface of the coax braid, causing RF interference and degrading the polarization and gain of the antenna. A 1:1 current balun should be used between coax and ladder line.[8] Including a balun not only prevents RF interference but reduces receive noise and increases performance[9] A length of at least 20 metres (66 ft) of 50 Ohm cable is recommended for operation without a balun.[10][11]

A transmatch (antenna tuner) is not required to use this antenna near its nominal design frequency of 14 MHz, and judicious length adjustments can sometimes include one other frequency band. All other frequencies require a transmatch. There are many variants of the G5RV antenna. Two variations of the G5RV design, called ZS6BKW and W0BTU, can match several more amateur bands between 3.5–28 MHz without a transmatch.[12][13]

References
  1. HF Antennas for all locations (L. Moxon, G6XN)
  2. G5RV multi-band antenna (Louis Varney, G5RV) http://www.astrosurf.com/luxorion/qsl-g5rv.htm
  3. The G5RV Multiband Antenna ... Up-to-Date (L. Varney, G5RV in The ARRL Antenna Compendium Vol. 1)
  4. (Heys, J. (G3BDQ). Practical Wire Antennas - Effective HF Designs for the Radio Amateur
  5. American Radio Relay League. ARRL Antenna Book, 21st ed. Chapter 7
  6. de Maw, D. (W1FB). Novice Antenna Notebook
  7. Carr, J. Practical Antenna Handbook, 4th Edition.
  8. Maxwell, W. (2010). Reflections III: Transmission Lines & Antennas
  9. VK4MDX. What I learned from building my own G5RV / ZS6BKW Antenna "Archived copy". Archived from the original on 2013-03-01. Retrieved 2013-01-12.CS1 maint: archived copy as title (link)
  10. Haerle, J. M. HF Antenna Systems: The Easy Way.
  11. Rüegger, M. (HB9ACC). (2008-05-24). Rund um die Antenne.
  12. Comtech Research. (2015). Truth about the G5RV Antenna and two other improved alternatives to this basic design.
  13. Vincent, M. (G3UKV). The ZS6BKW Multiband HF Antenna Revisited.


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