The G5RV antenna is still modern

Jindra OK1XR sent me his first post on our portal today. Since since 10. May our new competition is to take place with us, I decided to move her to Jindor for today, making his contribution the first to qualify for our competition. Thanks to Oliver MW3SDO for the Slovak HAM portal team.

Younger radio amateurs have already turned to me several times to see if I know where to get the data for the construction of the G5RV antenna.. Although the antenna has been published several times in various sources, however, all these sources are several years old and inaccessible to some younger amateurs. That's why I decided to make an excerpt from the article, which I have available. It's an old article 18 let.

G5RV – Louis Varney

MR Louis Varner G5RV, CX5RV antenna designer named after him G5RV received the first license with the brand 2ARV in 1927. For a year 1928 he still used the G5RV brand. He worked for Marconi Co. for thirty years. in the United Kingdom and since 1960 at a company providing professional technical consulting services in telecommunications. As an expert of this company, he has traveled all over the world and from most countries, which he visited, also broadcast as a radio amateur. Louis spent his well-deserved retirement with his wife in England from April to November and left for Uruquay 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 horseback riding. In Uruquay, he was a daily helper on the couches. Louis was fluent in English, Spanish, French, Italian and Portuguese. "No communication problem," Louis said. G5RV silent key 28. july 2000. So much about the author today world-famous and still for its simplicity and versatility popular antenna G5RV.

The antenna can also be used on 10.1, 14 a 24 MHz. Its dimensions allow installation on smaller plots, taking both halves (is fed symmetrically) they can be placed either in a straight line, or in the form of an inverted V. Because antennas of this type radiate most of the energy in two thirds of their length symmetrically to the fed center, the antenna radiator can deviate arbitrarily from the original direction on each side up to one sixth of its total length (turn down, up, to the side) without clear losses in overall radiation. The antenna can be halved (radiator and adaptive line) and then works on the bands from 7 do 28 MHz. If we connect both ends of the power supply at the bottom, we can then tune the antenna in the band, provided that it is well grounded or counterbalanced 1.8 MHz (at half version on 3.5 MHz). The efficiency of the antenna in this case is lower than with a conventional LW antenna. Unlike most multiband antennas, the G5RV is not designed as a half-wave dipole at the highest frequency used., but 3lambda / 2 middle powered LW band antenna 14 MHz. It works in this band 10.36 m long adjustment line (ladder) as an impedance transformer 1 : 1 and allows you to connect a symmetrical double line 75 ohms or coaxial cable 50 to 80 ohms with an acceptable CSV directly to the transmitter. In the other bands, the adaptive line "sets" its own radiator. The antenna is designed for frequency 14.15 MHz and its length is determined from the formula:

where "n" is the number of half-waves on the antenna (3lambda/2). Because the whole system tunes to resonance by the antenna member, dimension is used in practice 31.1 m. Because the antenna does not contain any tuned circuits (trapy), the electrical length of the horizontal emitter increases with increasing frequency. This decreases the vertical beam angle of the antenna with increasing frequency, which is very advantageous especially for DX connections. The radiation pattern varies from typically "dipole" to 3.5 MHz up to "long-time" at 14 to 28 MHz.

On all bands except 14 MHz, it is necessary to use an antenna tuner. When used for a band 1,8 MHz, when the power ends are connected, the antenna works like a "Marconi" or "T" antenna. The radiator is then mainly the vertical part of the antenna (ladder) and horizontal conductors serve as a capacitive "hat". It is good to make power lines (ladder) was constructed as vertically as possible.

Zone 3.5 MHz

Both halves of the horizontal emitter plus approx 5.18 m of the conductor of the matching line forms a slightly shortened and curved half-wave dipole. The rest of the matching line is an unwanted but irremovable reactance connected between the electrical center of the dipole and the power coaxial cable. Radiation diagram in the band 3.5 MHz corresponds to a half-wave dipole.

Zone 7 MHz

On 7 MHz horizontal emitter plus 4.87 m of the conduction line works as 2xlambda / 2 emitters in phase with the radiation diagram with slightly sharper lobes than the half-wave dipole would have.

Zone 10.1 MHz

On 10.1 MHz, the antenna functions as a 2xlambda / 2 collinear system in phase, with a radiation pattern approximately the same as on 7 MHz. After a good adaptation to the antenna member, the antenna is very efficient here.

Zone 14 MHz

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

Zone 18 MHz

On 18 The MHZ antenna works as a 2lambda powered in phase, combining a double collinear system gain and a relatively low vertical radiation angle.

Zone 21 MHz

On 21 MHz 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 customized very well and is effective for DX connections.

Zone 24 MHz

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

Zone 28 MHz

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

Construction

The dimensions of the antenna and the adjustment cable are on the antenna sketch. The horizontal radiator should be at least 10.36 m above the ground, which is the optimal lambda / 2 height for 14 MHz. If the antenna is made as an inverted V, so for maximum antenna efficiency, the angle between the two arms should not be less than 120 degrees. Adaptation lines should, if possible, always be designed as a "ladder", to have as few losses as possible. Because there will always be standing waves of current and voltage on it, its actual impedance is not important. If a black flat-screen TV is used instead of the air ladder 300 ohms, it is suitable that it is a perforated type (with cut-out windows). When using a TV double line, do not forget the shortening factor, which is 0.8 – 0.9 according to the type of double line. The double line has the disadvantage of aging and the associated changes in properties and worse mechanical resistance than the overhead line. The adjustment cable should hang vertically from the antenna at least 6 m long (if not possible in full length 10.36 m). The remaining part should be bent at about head height and routed to the coaxial power cable connection point. An impedance coaxial cable is recommended to power the antenna 50 – 75 ohms. The cable is connected directly to the end of the adapter cable (ladder) antennas. However, it is essential to use an antenna adapter between the end of the supply line and the transmitter. Instead of a coaxial cable, the antenna can be powered by an overhead line (ladder), whose construction is the same as the adaptive line. This can be bent and shaped as needed. In this case, it can be virtually any length from the antenna to the transmitter, the verticality of the length of the adjusting line must be maintained (10.36 m, minimum 6 m). In this case, a symmetrical antenna adapter is more suitable. When powered by a coaxial cable (advantage of cable passage through the walls, or pulling the cable along the wall) sometimes it happens, that current flows along the outside of the coaxial power supply. It can cause TVI. This can be eliminated this way, that just below the point of connection to the ladder, we make this feeder 8-10 threads with a diameter of about 15 cm. The threads are tightly covered with PVC insulating tape.

Horizontal part of the antenna (dipól) is with phosphorus-bronze. Nekoroduje, does not apply. It is also possible to use a lacquered CuL conductor with a diameter of 1–1.5 mm with a risk, that the antenna will slightly change its length due to the pulling of the wire. The car cable is unsuitable. It is heavy, the insulation cracks due to weather conditions and the unprotected cable corrodes in these places. The green military telephone cable is completely inappropriate (so-called. PéKáčko). After one winter, the frost-cracked cable is useless.

 

Adaptation line design (ladder)

The ladder is constructed of two enamelled Cu wires with a diameter of 0.8-1 mm. Straws proved to be the best spacers (stalks) of PVC for drinking lemonade. Not soft with a bending knee, but the classic bending of harder material. The pitch is 50 mm. We cut the straws to a length of approx 60 mm. Cu wires are best laid in parallel in the garden, heat the ends of the wires with a spark plug or lighter and pierce the straw with this hot end and move it further. This is how we proceed on both conductors until the required number of spacer bars is threaded. The straws are distributed symmetrically along the entire length of the ladder (approx 15 cm apart) and wrap a piece of Cu wire firmly under the straw and above it. (Specification: This involves fixing the spacer in place, to prevent the spacer from moving up and down. I dealt with it that way, that under the spacer I wrap the Cu ladder wire with a wire, for example from a coil, contactors, old transformer, etc.. with a diameter of approx 0.8 mm. You need to do something like that 5 threads, continue over the spacer and just above it again approx 5 threads. He's holding it!!! The second option is a drop from the glue gun. Below and above the spacer.) This fixes the straws in the required position. We solder cable lugs with a diameter to the ends of the wires 4 mm. Also at the ends of the dipole and the ends of the coaxial cable, then the antenna and the power coaxial cable are connected to the ladder with M4 screws. It is good to place the joints in a plastic tube (from drugs and the like) and fill with a melt gun or epoxy. The joints must be perfectly protected against the weather. The ranking created in this way is light, withstands all the vagaries of the weather, winds and storms. Tested over the years of operation of the G5RV antenna completely without defects. We can use Z-MATCH as an antenna adapter. The RAT-97 antenna adapter from OM3AI and OM3QQ published in Radiožurnál can be used with excellent results. 3/1997.

Jindra OK1XR

Sources

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