Antenna G5RV still modern

Jindra OK1XR sent me his first post on our portal today. Since our new competition is scheduled to take place from May 10th, I decided to move it around Jindorvi to today, which makes his contribution the first to qualify for our competition. Oliver MW3SDO thanks the Slovak HAM portal team.

Younger radio amateurs have already asked me several times whether I know where to get materials for the construction of the G5RV antenna. The antenna has been published several times in various sources, but all these sources are several years old and inaccessible to some younger amateurs. That's why I decided to make an extract from the article that I have available. It is an 18-year-old article.

G5RV – Louis Varney

MR Louis Varner G5RV, CX5RV designer of the antenna named after him G5RV received the first license with the brand 2ARV in 1927. From 1928 he still used the brand G5RV. He worked for Marconi Co. for thirty years. in Great Britain and since 1960 with a company providing professional technical consulting services in telecommunications. As an expert of this company, he traveled the whole world, and from most of the countries he visited, he also broadcast as a radio amateur. Louis spent his well-deserved pension from April to November with his wife in England and went to Uruguay for the winter, where he worked as a CX5RV. In addition to amateur radio, Louis had a number of other hobbies: oil painting, cooking, swimming and horse riding. In Uruquaya, he was a daily helper to the couch potatoes there in driving out the cattle. Louis was fluent in English, Spanish, French, Italian and Portuguese. "No communication problem" said Louis. G5RV silent key July 28, 2000. So much about the author of the G5RV antenna, now world-famous and still popular for its simplicity and universality.

The antenna can also be used on 10.1, 14 and 24 MHz without structural changes. Its dimensions allow installation even on smaller plots, while both halves (it is fed symmetrically) can be placed either in a straight line or in the shape of an inverted V. Since antennas of this type radiate most of the energy in two-thirds of their length symmetrically to the fed center, the antenna radiator can be arbitrarily deviated from the original direction (bend down, up, to the side) by up to one-sixth of its total length on each side without any obvious loss in overall radiation. The antenna can be halved (radiator and matching line) and then works on bands from 7 to 28 MHz. If we connect both ends of the power supply at the bottom, we can then tune the antenna with the antenna element even in the 1.8 MHz band (for the half version at 3.5 MHz) provided there is good grounding or a counterweight. In this case, the efficiency of the antenna is lower than that of a classic LW antenna. Unlike most multiband antennas, the G5RV is not designed as a half-wave dipole for the highest frequency used, but a 3lambda/2 center-fed LW antenna for the 14 MHz band. In this band, the 10.36 m long adaptation line (ladder) functions as an impedance line transformer 1 : 1 and allows you to connect a 75 ohm symmetrical twin line or a 50 to 80 ohm coaxial cable with an acceptable ČSV directly to the transmitter. On the other bands, the matching line is "adjusted" by its own radiator. The antenna is designed for a frequency of 14.15 MHz and its length is determined from the formula:

where "n" is the number of half-waves on the antenna (3lambda/2). Since the entire system is tuned to resonance with the antenna element, the dimension 31.1 m is used in practice. Since the antenna does not contain any tuning circuits (traps), the electrical length of the horizontal radiator increases with increasing frequency. This reduces the vertical radiation angle of the antenna as the frequency increases, which is very advantageous especially for DX connections. The radiation pattern varies from typically "dipole" at 3.5 MHz to "long wire" at 14 to 28 MHz.

On all bands except 14 MHz, it is necessary to use an antenna tuning element. When used for the 1.8 MHz band, when the feed ends are connected, the antenna functions as a "Marconi" or "T" antenna. The radiator is mainly the vertical part of the antenna (ladder) and the horizontal conductors serve as a capacitive "hat". It is good that the power line (ladder) should be constructed as vertically as possible.

3.5 MHz band

Both halves of the horizontal radiator plus about 5.18 m of matching line conductor form a slightly shortened and bent half-wave dipole. The rest of the matching line is unwanted but irremovable reactance connected between the electrical center of the dipole and the power coaxial cable. The radiation pattern in the 3.5 MHz band corresponds to a half-wave dipole.

Band 7 MHz

At 7 MHz, the horizontal emitter plus 4.87 m of matching line acts as a 2xlambda/2 emitter in phase with a radiation pattern with somewhat sharper lobes than a half-wave dipole would have.

Band 10.1 MHz

At 10.1 MHz, the antenna works as a collinear system 2xlambda/2 in phase, with a radiation pattern approximately the same as at 7 MHz. After a good adaptation of the antenna element, the antenna here is very effective.

14 MHz band

The antenna is designed for 14 MHz and the conditions for its operation are ideal. The radiation pattern has many lobes and the vertical radiation angle is about 14", which is effective for DX connections..

18 MHz band

At 18 MHZ, the antenna functions as a 2lambda powered in phase, combining the gain of a double collinear system and a relatively low vertical radiation angle.

21 MHz band

At 21 MHz, the antenna works as 5lambda/2LW. The radiation pattern has many lobes and a very effective low vertical radiation angle. Although there is a relatively large real impedance at the end of the matching line, the system can be matched very well and is effective for DX connections.

24 MHz band

At 24 MHz, the antenna works similarly to 21 MHz.

28 MHz band

At 28 MHz, the antenna works as two LW antennas, each 3lambda/2 powered in phase. The radiation pattern is similar to that of the 3lambda/2 LW antenna.

Construction

The dimensions of the antenna and the adjustment line are on the sketch of the antenna. The horizontal radiator should be at a height of at least 10.36 m above the ground, which is the optimal height lambda/2 for 14 MHz. If the antenna is made as an inverted V, the angle between the two arms should not be less than 120 degrees for the maximum efficiency of the antenna. If possible, the adjustment line should always be constructed as a "ladder" in order to have as little loss as possible. Since there will always be standing waves of current and voltage on it, its actual impedance is not important. If a black flat TV cable of 300 ohms is used instead of an aerial ladder, it is advisable that it be a perforated type (with cut-out windows). When using a dual-line TV, do not forget the shortening factor, which is 0.8 - 0.9 depending on the type of dual-line. The double line has the disadvantage of aging and associated changes in properties and worse mechanical resistance than overhead lines. The adjustment line should hang vertically from the antenna at least 6 m long (if not possible in the entire length of 10.36 m). The remaining part should be bent at about the height of the head and led to the point of connection of the power coaxial cable. A coaxial cable with an impedance of 50-75 ohms is recommended for powering the antenna. The cable is connected directly to the end of the adaptation line (ladder) of the antenna. However, the use of an antenna adapter between the end of the power line and the transmitter is essential. Instead of a coaxial cable, the antenna can be powered by an aerial line (ladder), the construction of which is the same as the adaptation line. This can already be folded in different ways and shaped as needed. In such a case, it can be practically any length from the antenna to the transmitter, the verticality of the length of the adaptation line (10.36 m, minimum 6 m) must be maintained. In this case, a symmetrical antenna matching element is more suitable. When feeding with a coaxial cable (advantage of passing the cable through the wall, or pulling the cable along the wall with a rail), it sometimes happens that the current flows on the outside of the coaxial feeder. It can be caused by TVI. This can be removed by making 8–10 turns of this feeder with a diameter of about 15 cm just below the point of connection to the ladder. The threads are tightly wrapped with PVC insulating tape.

The horizontal part of the antenna (dipole) is made of phosphor bronze. It does not corrode, it does not pull out. A lacquered CuL conductor with a diameter of 1–1.5 mm can also be used, with the risk that the antenna will change its length a little due to pulling out the wire. A car cable is not suitable. It is heavy, the insulation cracks due to weather conditions and the unprotected cable corrodes in these places. The green military telephone cable (so-called PéKáčko) is completely inappropriate. After one winter, a frost-cracked cable is useless.

Construction of the adjustment line (ladder)

The ladder is constructed from two enameled Cu wires with a diameter of 0.8–1 mm. PVC straws for drinking lemonade have proven to be the best spacers. Not a soft one with a bending collar, but a classic non-bending one made of harder material. The pitch of the ladder is 50 mm. Cut the straws to a length of approx. 60 mm. It is best to stretch the Cu wires simultaneously in the garden, heat the ends of the wires with a candle or a lighter and pierce the straw with this hot end and move it further. We proceed in this way on both conductors until the necessary amount of spacer bars is strung. The straws are placed symmetrically along the entire length of the ladder (approx. 15 cm apart) and a piece of Cu wire is tightly wound under the straw and above it. (Clarification: This is about fixing the spacer in a given place, so that it is impossible to move the spacer up and down. I solved it by wrapping the conductor of the Cu ladder under the spacer with a wire, for example from a coil, contactor, old transformer, etc., with a diameter of about 0.8 mm. It is necessary to make about 5 turns, continue over the spacer and just above it again about 5 turns. It holds!!! The second option is drop from the glue gun. Under and above the spacer.) This fixes the straws in the required position. At the ends of the wires we solder cable eyes with a diameter of 4 mm. On the ends of the dipole and the ends of the coaxial cable as well, then the antenna and the power coaxial cable are connected with the ladder of the M4 screw. It is a good idea to place the joints in a plastic tube (from medicines and the like) and cover them with a melt gun or epoxy. The joints must be perfectly protected against the effects of the weather. The ladder created in this way is light, it can withstand all vagaries of weather, winds and gales. Tested for years of operation of the G5RV antenna with absolutely no defects. We can use Z-MATCH as an antenna matching element. The antenna adapter RAT-97 from OM3AI and OM3QQ published in Radiožurnál 3/1997 can be used with excellent results.

Springs

Amateur radio A12/1985
http://www.radioworks.com/Varney/poles.htm
www.radioworks.com/Varney/G5RVmain.htm
www.kwarc.on.ca/g5rv_sk.html