Once I heard Don Wallace W6AM and a neighbor comparing antennas on 20 meters. Don was running one of his rhombics aimed toward Europe. His neighbor said he was running a 5 element mono-band yagi at 150 feet (I think it was). Anyway while I was listening they compared the two antennas getting comparative signal reports from many European stations. Don's rhombic was almost always at least 20dB stronger than his neighbor who was running the 5 element yagi at 150 feet.
I understand that theory (EZNEC) does not predict this result, but what happens on-the-air is what separates the big guns from the little pistols. A Rhombic will truly open and close the band.
A Rhombic Antenna = The highest development of a long-wire antenna.
Each antenna a K0UO 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. My four antennas each cover an area equal to five football fields. 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 amateur use. K3LR may have more gain with beams using 4 over 4 over 4 on 40 meters, but he needs to rotate.
Dick AD4U from eham.net
At the W8IJ antenna page, he makes some interesting points in his modeling of the large rhombic antenna. Note: He is not overly excited about its merits or gain per area of antenna space used. He states, "Most of the rhombic's performance limitations come from the high levels of spurious lobes and the poor efficiency (50%), especially over normal soil. The rhombic has one of the poorest gain-per-acre rankings of any high gain HF antenna array."
On the other hand, a rhombic antenna does have the distinct advantage of working over very wide frequency ranges with flat SWR and high gain, something a basic mono-band yagi can never do. The rhombic is also a simple antenna, requiring only four supports (three supports for the Vee beam, and one support for inverted Vee derivatives).
However some of those points can be very positive for day-to-day use of the antenna in amateur radio service, remember amateurs are not point-to-point shortwave broadcasters, military or wire services, Amateurs just want to make QSOs! Also most amateur radio operators don't have tens of thousands of dollars to spend on tall towers and stacked mono-band beams, or the ability to climb and maintain such structures. Rhombic antennas were the ultimate antenna design back in the Golden Age of Wireless. However, building one required a large tract of land and a number of tall telephone poles, because they have dimensions several times the wavelength. To most amateurs the positive thing is there are no large mono-band antennas to maintain, or rotators to fix, and rhombics allows for instantaneous direction and band switching. They normally can be installed at very low cost, if you have trees to hang them from, all that is needed is a lot of wire and time! Also 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. So the rhombic antenna does have the very distinct advantage of working over very wide frequency ranges with flat SWR and high gain.
