The Mighty Rhombic is the "KING of Wire Antennas".
The ARRL, RSGB, Switzerland, and so many other amateur radio organizations use the Diamond Logo, which is in fact a Rhombic antenna.
K0UO is working on the "Lost Art of Rhombics" with four of these large wire antennas, and two 1200 foot Vee-Beams at the Kansas QTH. These are beaming to the eight main DX areas, with phasing for more steering.
See my call on qrz.com then type in the call K0UO for more information and photos. Each Rhombic antenna uses over 1/2 Mile of 3/8" cable. They are erected on 100 foot wooden utility poles, also the site has two large Vee Beam antennas which are over 1200 foot long each. Miles of wire in the air and on the Air. Build Them and the DX will Come!
At K0UO in 2021, a 40-6 meter vertical polarized 1/2 Rhombic antenna was installed at a center height of 160 feet. This antenna is dependent on the quality of the galvanic ground connection to the earth (Ohmic resistance of the ground rod system), in this case the antenna is using a 5400 foot deep oil-well casing as a ground (mostly for lightning protection). Also the red soil on this site, is high in iron, and has great ground Electrical Conductivity (EC)
The antenna is 10 waves long on 40 meters (1350 feet) and centered at 160 feet high. The antenna is made using triple galvanized wire rope cable with a diameter of 1/4 of an inch, so it's just not just Steel, it's triple coated with galvanized. The galvanized cable is made of zinc and other higher conductive components. Most commercial AM broadcast towers are zinc-plated.All the big wire antennas are tensioned stretched to 2500 lbs of pull.
This antenna can be terminated by using a large 450 ohm non-inductive resistor, see below.
The vertical polarized 1/2 Rhombic has a wider beam, but less gain than the full Rhombic, however it only requires on one tall support, so just make it longer for more gain!
The directivity is in the plane of the legs. Feeding one end with a 9:1 balun and the other end open produces a bi-directional signal. While terminating the far end produces a unidirectional signal at the terminating end. This high gain antenna is used where low angle of radiation is needed.
This antenna also has some higher angle, which can be an advantage for amateur use, for talking to nearer stations.