The "KING of Wire Antennas" is a Rhombic"
Updated: Nov 24, 2021
K0UO is working on the "Lost Art of Rhombics" with three of these large wire antennas at the Kansas QTH beaming at the 6 main DX areas, and phasing for more steering.The "KING of Wire Antennas" is a W1AW type Rhombic. Each antenna was built for 40 meters and above, with over 600 to 700 foot per-leg and +1200' end to end, 6 to 7 Acres each on 80 to 100 foot wood poles, The Front to Back is like a brick wall, maybe +45dB or more. That makes them 4 to 6 Wave-Lengths long on each of the four sides or 16 to 24 wave-lengths total for 40 meters, these may be the largest 40 meter Rhombic antennas in current ham use. In the 1950s to 1970s W6AM had many 1000 footers and one was 1500ft, TF4M put up a larger one at one time, and Roy W7YRV/SK had nine at one time and he developed the X Rhombic, which he had one for every 20 degrees. That was a truly remarkable accomplishment for an amateur station (You must see his page, great info w7yrv.blogspot.com/2013/). It was an extreme pleasure for K0UO to meet Roy, even in his 90's, he was still an encyclopedia of knowledge when it comes to very high gain antennas. K0UO is very privileged that W7YRV has entrusted him with the schematics, drawing, and photos of these fabulous antennas. W1VDE Roger in OR has six and is on the air daily, alsoVK3MO, and in Texas N5APR and W5BY Jeff, have a few at their ranch's, KL7KK in AK has one along with a few VK's, and V55V (V55W) in Namibia had 2 but they are now down. The gain over the full size 40 meter wire 2 element beam at 100 feet high, is truly unbelievable, Gain before Amplification. The QTH also has two long 1200' Vee-beams, on 75-95 foot woodenpoles. The antennas are currently assisting a group with a project using TDoA (Time Difference of Arrival ) Direction Finding (DF) checking integrated statistical localization algorithm which allows the localization of HF transmitters based on AoA (Angle of Arrival).
Most Radio Amateurs don't know that a key concept with traveling-wave type antennas like a Rhombic, that the current and voltage levels are the same everywhere along the antenna conductors, so no standing waves on the antenna itself. The rhombic antenna therefore has the distinct advantage of working over very wide frequency ranges. By using switches there is No waiting for a rotator to turn, just every direction, every band, every time with the sites multiple antennas.
A horizontal rhombic antenna radiates horizontally polarized radio waves at a low elevation angle off the pointy ends of the antenna. A rhombic antenna does have the very distinct advantage of working over very wide frequency ranges with good SWR and gain, something a basic monoband Yagi can never do. The rhombic has major advantages over other antennas. It is easy to construct and somewhat non-critical of dimensions. It offers very wide bandwidth performance, being competitive with large log periodic arrays. If a ham needs an easy-to-install very broadband antenna, that can easily handle high power and if they are not particularly worried about efficiency, a rhombic is a worthwhile antenna to consider. The many spurious lobes, while they do rob significant power from the main lobe, can also fill in other directions while transmitting. This is a plus for Hams, if one can align the side lobes with populated areas. In a large properly designed rhombic.
Time must be spent on the layout of the antenna, you must have a plan on what parts of the world that you want the main beams headed at. The lobe is only 20 degrees wide.
Then get the area ready for the install the above photo is my Cat bulldozer clearing out the area. Each of my antennas cover nearly 7 acres.
Getting the hardware ready
1000 foot of 1 5/8" and 7/8" hard-line to the main control box, then 600 ohm open wire feeders
Miles of 3/8 in cable
The 100 foot poles are over 36" diameter at the base 6000 to 8000 lbs each
One of the control boxes which is over 1500 foot from the shack
A open wire feed system
A smaller 3wl per side, still 16dBi and 28dB FB, my antennas are 4 to 6 waves on each side.
Below: The key concept with traveling-wave antennas is that there are no standing waves, which means that the current and voltage levels are the same everywhere along the antenna conductors. The animation below shows how a traveling wave antenna works (all types of traveling wave antennas). Due to ground resistance the electric field of the radio wave (E, big red arrows) is at an angle θ to the vertical, creating a horizontal component parallel to the antenna wire (small red arrows). The horizontal electric field creates a traveling wave of oscillating current (I, blue line) and voltage along the wire, which increases in amplitude with distance from the end. When it reaches the driven end (left), the current passes through the transmission line to the receiver. Radio waves in the other direction, toward the terminated end, create traveling waves which are absorbed by the terminating resistor R, so the antenna has a unidirectional pattern.
a directional antenna in which a traveling wave of electromagnetic oscillations is propagated along its geometric axis. Traveling-wave antennas are made either with discrete radiators placed along the axis at a certain distance from one another or in the form of a continuous radiator that extends in the direction of the axis. (The latter is considered as the sum of discrete radiators adjoining one another.) The Yagi antenna and the helical antenna belong to the first category; the dielectric rod antenna and the Beverage antenna belong to the second. There are also traveling-wave antennas consisting of several elements, each of which is a traveling-wave antenna of the second type (the rhombic antenna and others). This type of antenna is used in receiving and transmitting installations for all wavelengths of the radio band. The traveling-wave antenna has its maximum radiation (reception) in the direction of its axis. The directivity is D = kl/λ where / is the length of the antenna, λ is the wavelength, and k is a coefficient that depends on the directivity of the individual radiating element, the phase velocity of the traveling wave, the relationships of the current amplitudes in the radiating elements, and other factors. The value of k usually lies in a range from 4 to 8. The directivity reaches a maximum when the phase velocity v of the traveling wave is somewhat less than the velocity of light c and equal to v = c • 2l/(2/ + λ) The typical characteristics of a traveling-wave antenna are the axially symmetrical shape of its three-dimensional radiation pattern (that is, the shape of the pattern is the same in any plane passing through the antenna’s axis) and the maintenance of adequate directivity (in the majority of traveling-wave antennas) over a broad wavelength range. The first characteristic becomes increasingly evident with an increase in the ratio l/λ and the axial symmetry of the radiation pattern of each radiating element. REFERENCE Aizenberg, G. Z. Antenny ul’trakorotkikh voln [part 1]. Moscow, 1957. G. Z. AIZENBERG and O. N. TERESHIN
How do the Rhombics preform?
A detailed modeling analysis of these rhombics has been done. Narda meters are used for testing both E and H fields in the far field, but the on the air tests and QSO's show the real power of these antennas. With each antenna having more than 2200 feet of wire, “The RF Gotta-Go-Somewhere”. Note a full size 2 element 40 meter phased wire beam at 100 ft was used for a reference antenna.
Now that is Real GAIN
The tower in the back is 195 foot tall and 1000 feet from this pole.