The G5RV All Band Antenna

The G5RV is a very popular antenna on the HF amateur band today. Despite it's widespread use on the bands, there are some myths and misconceptions concerning the G5RV that seem to have a life of their own. Working with text from the ARRL "Antenna Compendium", Volume 1, I would like to shed some light on this versatile antenna

 First, from Louis Varney, G5RV, of West Sussex, UK, here is some back-ground and insights into the G5RV.

"The G5RV antenna, with its special feeder arrangement, is a multiband center-fed antenna capable of efficient operation on all HF bands from 3.5 to 28 MHz. Its dimensions are specifically designed so it can be installed in areas of limited space, but which can accommodate a reasonably straight run of 102 ft for the flattop.... In contradistinction to multiband antennas in general, the full-sized G5RV antenna was NOT designed as a half-wave dipole on the lowest frequency of operation, but as a 3/2-wave center-fed long-wire antenna on 14 MHz, where the 34 ft open-wire matching section functions as a 1:1 impedance transformer."

"LENGTH (ft) = 492(n-.05)/f(MHz) = (492 x 2.95)/14.15 = 102.57 ft (31.27 m)

where n = the number of half wavelengths of the wire (flat-top).

"Because the whole system will be brought to resonance by the use of a matching network in practice, the antenna is cut to 102 ft." As the antenna does not make use of traps or ferrite beads, the dipole portion becomes progressively longer in electrical length with increasing frequency. This effect confers certain advantages over a trap or ferrite-bead loaded dipole because, with increasing electrical length, the major lobes of the vertical component of the polar diagram tend to be lowered as the operating frequency is increased. Thus, from 14 MHz up, most of the energy radiated in the vertical plane is at angles suitable for working DX. Furthermore, the polar diagram changes with increasing frequency from atypical half-wave dipole pattern at 3.5 MHz and a two half-wave in-phase pattern at 7 and 10 MHz to that of a long-wire pattern at 14, 18, 21, 24 and28 MHz. Although the impedance match for 75-ohm twin-lead or 80-ohm coaxial cable at the base of the matching section is good on 14 MHz, and even the use of 50-ohm coaxial cable results in only about a 1.8:1 SWR on this band, the use of a suitable matching network is necessary on all the other HF bands. This is because the antenna plus the matching section will present a REACTIVE load to the feeder on those bands

Thus, the use of the correct type of matching network is essential in order to ensure the maximum transfer of power to the antenna from a typical transceiver having a 50-ohm coaxial (unbalanced) output. this means unbalanced input to balanced output if twin-lead feed is used, or unbalanced to unbalanced if coaxial feeder is used. A matching network is also employed to satisfy the stringent load conditions demanded by such modern equipment that has an automatic level control system. The system senses the SWR condition present at the solid state transmitter output stage to protect it from damage, which could be caused by a reactive load having an SWR of more than 2:1."

The general theory of operation follows. As I can't put the diagrams in the file, I will paraphrase the text from the ARRL "Antenna Compendium", Volume 1, which is a great book for the antenna fan (NOT A COMMERCIAL, JUST ANOBSERVATION..[WKH]). Please keep in mind that this is the THEORETICAL information, and the actual operation will depend on placement, height aboveground, metal siding, power lines, trees, UFO flight patterns, Etc.

3.5 MHz: On this band, the antenna acts as a shortened half-wave flat-top, with about 17 ft of the total length made up by the matching section. The remainder of the matching section introduces an unavoidable reactance to the antenna between the feedpoint and the feedline. The antenna pattern is effectively the same as a half-wave dipole on this band.

7 MHz: The flat-top, plus 16 ft of the matching section makes up a partially folded up 2 half waves in phase, (collinear) antenna. The antenna pattern is somewhat sharper than a dipole because of its collinear characteristics. The match is somewhat degraded due to the unavoidable reactance introduced by the extra length in the matching section. This reactance can be easily tuned out with an antenna tuning unit (ATU).

10 MHz: On this band, the antenna functions as a 2 half-wave collinear. It is very effective, but the reactance presented at the feedpoint requires a good ATU. The pattern is basically identical to the 7 MHz pattern.

14 MHz: This band is where the G5RV really shines. The antenna is operating as a 3/2 wave long, center-fed antenna with a multi-lobed, low angle pattern of about 14 degrees elevation, which is very effective for working DX on this, the most popular DX band. The antenna presents a 90-ohm load with basically no reactance present. Even the use of a 50-ohm coaxial feed will present a SWR of only about 1.8:1, easily tuned out with an ATU.

18 MHz: The antenna performs as 2 full-waves in phase, combining a lower angle with the broadside gain of a collinear array. The load is high-Z,w ith somewhat low reactance

21 MHz: On this band, the antenna works as a 5/2-wave, center-fed longwire. This produces a multi-lobed, low angle radiator, with a high-Z resistive load. When matched with the ATU, it makes a highly effective antenna for DX contacts.

24 MHz: The antenna again functions effectively as a 5/2-wave long wire, but due to the shift in the position of the current loops on the array, the load is resistive, approximating the load on 14 MHz. Again, the pattern is multi-lobed, with a low radiation angle.

28 MHz: On this band, the antenna acts as a 3-wave, center-fed long wire. The pattern is similar to 21 or 24 MHz, but with additional gain due to the collinear effect obtained by feeding two 3/2-wave antennas in phase. The load is high-Z, with low reactance.

 THE MATCHING SECTION: It is recommended that the matching section be constructed of open-wire feeder for minimum loss, as it always carries a standing wave on it. Due to the standing wave on it, the actual impedance is unimportant. A satisfactory construction technique for the open wire line matching section would be to make your own spreaders out of scrap Lucite, or similar plastic of low dielectric loss. The plastic strips would be cut about 2 inches long, 3/8 inch to 1/2 inch wide, and be notched on the ends to fit #14 wire. The spreaders would be drilled about 1/2 inch in from each end for the binding (tie) wires, and the spacers would be spaced 12 inches center-to-center. The next most-desirable matching section would be made from window-type open wire line, either 300-ohm, or 450-ohm. This is basically a ribbon line, like heavy duty TV-type twin lead, with #16 to #20 wire, and "windows" cut in the insulation every 4 to 6 inches. The advantage of the "window" line is that the conductors won't short together if the line twists in a high wind Lastly, and the least desirable, (although it will work), is "TV-type" twin lead. The main disadvantage of the TV-type twin lead is durability. The conductors on the twin lead are usually #22 to #28 gauge, and the plastic used for the insulation deteriorates faster in the sun and/or rain. The advantage of it is that it is readily available at electronics outlets, or even most department/home improvement stores. The quality is proportional to price, if a choice is available. Do not use the "shielded" twin lead. The shield will degrade the matching section, especially on 3.5 or7 MHz

 MATCHING SECTION LENGTH: The length of the matching section is an ELECTRICAL half-wave on 14 MHz. The actual physical length is determined by the following formula:

 The type of line and the dielectric properties of its insulation determine the velocity factor. For the three types of line discussed so far, the VF is:

By substituting the VF in the formula, and calculating for a center frequency of 14.15 MHz, you come up with the following matching section lengths:

This matching section is connected to the center of the array, and allowed to descend vertically at least 20 ft or more, if possible. It can then be bent and tied off to a suitable post or line, and connected to the coaxial line, which is run to the shack, and the ATU.

 Doug DeMaw, W1FB, in his W1FB'S ANTENNA NOTEBOOK, states that the G5RV can be fed directly with open wire to the ATU. If this is done, the antenna will load on all bands with no problems. In this case, the ATU needs to have a balanced output to accommodate the balanced line. This would lend itself to the portable operator, who could use "TV"-type twin lead, and a small tuner designed for balanced feed on all the HF bands. This would be an elegant solution for a campsite or cottage, reducing the bulk of the gear to be carried. A convenient length of twin lead, allowing for the VF, would be 72 ft. The whole antenna would coil up into a small bucket, or even a backpack with #18 wire. In closing, if you need a good , multi-band, and unobtrusive antler for your station, give the G5RV a try. Best of luck, and have fun!

 73, Keith, KE2DI

 The 160 6 Meter G5RV, which is a Double-Scaled G5RV, (G5RV)x2, can be used with improved performance in the upper end of the HF spectrum by configuring it as a Vee-Beam. Electrically, the (G5RV)x2 is a 3/2-wavedipole for the 40 Meter band, or .75-wave/side. By bringing the ends in towards each other, you can form it into a Vee-Beam, which will show sharper bi-directional characteristics, and gain in the direction through the bisector. To utilize a Vee-Beam through a wide range of the HF spectrum, one should design the antenna for the middle of the range desired. Typically, if the desired band(s) one wants to improve are the 20 - 10Meter bands, then the apex angle is calculated for the 15-Meter band. Using this logic, the leg-length is then 2.25-wave, which requires an included angle of around 70-degrees. Using a 70-degree angle would result in an antenna, held up with3 supports, forming a equilateral triangle, (NOT a Right Triangle!), with legs of 102', 102' and 167'. It is a wide, but shallow triangle, with an apex "height" of 58.5 feet. The directivity is along the plane of the apex "height", and is bi-directional.

 The approximate, (VERY approximate!), gain of such an array is shown below in tabulated form for the upper HF bands:

 These "gain" figures are optimistic, and based on the apex-angle being correct for the given leg length, which is not the case here. The gain will be closest to the listed figure on the 15 Meter band, and off the most on the 40 Meter band, but should be within a dB or so. These figures are close to the gain of a small tri-bander, and the beamwidths such that one could cover most of the USA from the North East with one installation. Get the most out of your wire, and try it out on Field Day! We at the BARK Field Day group, (KB2UFY), will be looking for YOU!

 73, Keith, KE2DI, F.D.

Chairman, Brockport Amateur Radio Klub 

 The G5RV multiband antenna is a very popular design on the HF bands. The "common" G5RV is configured as a 3/2-wave dipole on 20meters, and works as either a shortened dipole, or a collinear-fed longwire on the other bands. In this configuration, the overall length is 102 ft, with a 28 to 34 foot matching line. In some cases, this is still too large to fit in one's yard, and not everyone can convince their neighbors to allow one to stretch the wire across property lines. In this case, a 1/2-size version, covering 7 to 28MHz is useable. Conversely, some amateurs would like to have 1.8 MHz capability, and have the 204 foot length necessary for this array. I have dimensions included here for both the half-size and double-size G5RV antennas.

[All of the above-mentioned antennas will work on the 6-Meter band, sometimes without an ATU.]

 Of the listed antennas above, the 7-28 MHz version was referred to in Louis, G5RV's article in the ARRL "ANTENNA COMPENDIUM" Volume 1. The 1.8 - 28 MHz version is in use at Evhan, WB2ELB's QTH, (with a single feedline, directly matched with the internal ATU in his Kenwood, and the 3.5-28 MHz version in use by more local hams than I can remember right now. Just for reference, the "window"-type ladder line is available at most amateur dealers, over-the-counter, or mail-order, and the polycarbonate (Lucite) plastic for the spreaders for home-built open wire is available at any major plastic supplier at scrap prices.