"KING of Wire Antennas" is a Rhombic"
- skylarkcolo
- Nov 1, 2024
- 20 min read
Updated: 21 hours ago
K0UO is involved in the "Lost Art of Rhombics", utilizing four large wire antennas at the Kansas QTH to target the eight main DX areas, with phasing for enhanced steering. These are currently the largest wire-type amateur radio antennas in use worldwide. K0UO designed and constructed the entire station, including the massive Rhombic and beverage antennas, conducted far field measurements, and has access to over 1,200 acres of owned or leased land surrounding the antenna farm site for far field testing. With an extensive array of towers and antennas, it is a big antenna farm.
The K0UO Rhombic farm an antenna test range site "Antenna University" utilizes the 4KS Walz airport, and its surrounding area as a practical learning environment for Scientific, Technical, Engineering, & Mathematics (STEM) antenna projects in an outdoor real-world setting. If group has a University or school has an antenna research STEM program, let me know.
The KØUO Rhombic Antenna Farm in Kansas, consist of many acres, with "Miles of Wire in the Air & On the Air". Best known as an antenna Experimenter, Ragchewer 1st and DXer for fun! "It takes years of Passion, Hard work, and Commitment to build a great station".
The "KING of Wire Antennas" is a K0UO type Rhombic.
Each large antenna was constructed for 40 meters and above, with each leg measuring 600 to 700 feet, and spanning more than 1200 feet from end to end of the diamond array. They occupy about 7 acres each, mounted on 80 to 100-foot tall wooden power-line poles. The front-to-back ratio is like a brick wall, exceeding +40db. This means for 40 meters, they measure 4 to 6 wavelengths long on each of the four sides, (or 16 to 24 wavelengths in total for 40 meters). All using 3/8" Triple Galvanized Wire Rope Cable used for the antenna wire.
These are the largest 40-meter amateur radio Rhombic antennas currently in use. Additionally, the site has three V-Beams arrays (1200 foot on each side or 1/2 of a rhombic) for more directions.
To put it in perspective, my four rhombic antennas each cover an area equal to five football fields, or about 7 acres each, and over 3.5 acres for each V-Beam (You need acres). These are the world's largest ham radio wire antenna arrays now in use I'm very fortunate to to be able to use over 1200 acres surrounding the antenna site, for far field HF antenna measurements, for testing the performance of these and other antennas.
A Rhombic Array has high gain, using a very low radiation angle transmit pattern, for long distance (DX) communications.
The site uses repurposed equipment from W6AM's old station, W7YRV, Voice of America, The BBC and other legendary stations.
Others with Rhombic Arrays
W6AM
In the 1950s to 1970s W6AM had many 1000 footers, and one was 1500ft. In fact I am still using some of W6AM's hardware on my antennas, a living memory to W6AM, On the Air Daily.
Roy W7YRV/SK had nine at one time, and he developed the X Rhombic, which he had built one for every 20 degrees, (18 total). 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 parts, schematics, drawing, and photos of these fabulous antennas.
W1VDE Roger in OR has six and is on the air daily, also VK3MO, and in Texas N5APR and W5BY Jeff, had 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, and TF4M also put up a large HF one at one time.
The Old V55W station in Namibia was about the same size as my Rhombics but not as high.
Martin Walter, V51W, near Omaruru, Namibia, has spent the past 2 decades improving his station, which likely accounts for his V55V station’s increasingly better signal.
After trying all possible antenna systems, he is convinced that his wire rhombic antennas are the best choice. He uses three of them; two that are 160 meters on each leg to the US and Europe, and one with 80-meter legs, also aimed at Europe. Their gain depends on the band and can top 10 dB.
V55V was used for countless contest and DXpedition activities during the past years, but now, Walter is planning to shut down the station and move back to Germany.
Ian VK3MO sent me this overview in Aug. of 2025, "My single rhombic is still in the air and functional. My rhombic is supported on 4 X 132ft steel towers guyed with non metallic guys. The rhombics are stacked with one at 70ft and the other at 132ft. There is 550ft per leg giving a total radiating wire length of 4400ft. My original objective was to build an antenna for 20M with gain. It obviously works well on the other bands. I run open wire feeders from each end of the rhombic back to the centre where I have a large TCI balun and a tuner. I then have a 600ft run of LDF-450 Heliax back to the shack. (it is a shame to lose a dB on the feedline).
I use 2.84mm diameter hard drawn copper wire for the antenna and feedline. It has survived thirty years without breakages. I started out using stranded copperweld wire and it failed after two years. It developed rust bubbles and started breaking regularly. I pulled it down and started again with the hard drawn copper and not a single problem in thirty years. (I suspect the stranded copperweld wire may have been poor quality. I purchased it from the wireman and the results were disappointing. My rhombic is aimed at New York". 73
Engineering Insight
Rhombics are like the diesel trucks of antenna design — rugged, reliable, and built for long hauls. A Rhombic array can make your ham station a "Super Station". But if you need agility, precision, or compactness, other designs may suit you better. That said, big rhombics wire arrays still hold their own in niche applications, like DoD, Broadcasting, and amateur ham radio where bandwidth, gain, cost, and simplicity matter most.
The rhombic is the largest and most refined of the long-wire antennas, consisting of two Vs, open-end to open-end. The result is 4 wires contributing aligned lobes for higher gain and narrower beamwidth. And the rhombic suppresses unwanted side lobes better than the V antenna.
I am now using the biggest HF Re-entrant Rhombic arrays, and they are the highest forward gain HF antennas with its 90% efficiency, now with very high gain, and low noise receive characteristics. So, the Rhombic Arrays can beat the massive stacked HF beam arrays that I had up before.
In testing the gain compared to my full size 40 meter two element wire beam at 100 feet high, is truly unbelievable, Gain before Amplification
Major Advantage, all long Traveling wave antennas are known for fantastic Improvements in the reduction of signal fading, which is called QSB by amateur radio operators, for both transmit or receive.
It is like Diversity, theses large arrays cover a lot of area. My station uses over a mile of wire, so you are both listening and transmitting signals coming and going at different angles. Signal-to-noise ratio (S+N/N ratio, or SNR) is one technical aspect not too many amateurs give a second thought about, however if you can't hear them you can't work them. This is very apparent on audio reception,long Traveling wave antennas eliminates much of the audio amplitude fading for both transmit or receive. The RF signal is almost never in a stable phase relationship at both places at the same time. This means the signal will have random phase and amplitude differences. The arrival angle and polarization of incoming signals will change. This generally results in the fading, by having many wavelengths of wire in the air, the chances are that while one experiences a fade, the other will not. The power is in the diversity size of the array and what you can now hear with out QSB fading. Traveling wave antennas are just quieter and have substantial noise reduction. That is why so many people use the Beverage receive antennas.
In 2021 I added, a fourth array, a vertical polarized, 1/2 Rhombic antenna at 160 foot, which is dependent on the quality of the ground connection to the earth (Ohmic resistance of the ground rod system) using a 5400 foot deep old oil casing and pipelines under it to reduce ground loss. The antenna is 10 waves on 40 meters (1350 feet) centered at 160 feet, for more info see the post in this blog the about vertical polarized Rhombic antennas.
V BEAMS (Vee)
The QTH also has three long 1200' V-beams, installed on 75-100 foot wooden-poles, a V Beam is just 1/2 of a Rhombic. These 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). (That project has ended 2023)
Why I went to the big Rhombic arrays
I would have saved a lot of money$$$, time, frustration, and regret, if I had not put up the 200 ft rotating towers, with all the aluminum beams. This was back in the late eighties and 1990s, when my wife moved back to the Kansas Ranch, and I started building the dream station.
For first 15 years on the ranch, I spent each spring, summer, and fall working on mechanical things. It was just non-stop repairs and replacement of components.
Each winter the big Arctic ice and wind storm,s out on the high wide open prairies, east of the Rocky Mountains in Western Kansas, destroyed every aluminum or fiberglass antenna that was installed, even the commercial ones rated for 125 mph.
ICE LOADING at the K0UO Antennas, that is why I took down the other tall towers and standard aluminum beams, the Rhombics with the heavy cables using commercial hardware, and vibration dampers stay up in the ice.
Replacing aluminum elements and 3-in booms, that got bent by all the ice and wind from the previous winner. I was fixing rotors, mounting plates, an assembling new antennas, while missing thousands of QSOs contacts, because of all the work. The work was required just to build the station back, and keep it going. Also it was very expensive, and frustrating to be replacing something that was new last year.
I was a younger man then, but it was very dangerous working on a four Element 40 meter beam, at 200 ft, that had broken elements and booms. The pieces could drop and take the next sets of guy wires below you with it. While you're on top of the tower, not a good thing.
I spent a lot of years rigging those beam antennas, that was very hard work, and at elevation on the Towers.
FACT: The re-entrant K0UO Rhombic Arrays have much more gain than the massive stacked HF yagi beam arrays, that I had up previously.
The Rhombic Wire Arrays using robust commercial power line components, complete with switches for immediate direction changes. In over 20 years, the antennas themselves have never failed. Occasionally, there are issues with coax connections or the control boxes, but these are safely accessible on the ground. The best part is that even at my older age, I can spend 99% of my free time On the Air, rather than fixing broken antennas and towers!
The big Traveling Wave antennas, like the Rhombic and V-beams have no SWR, and are super quiet when receiving, see below. Another big bonus is no waiting for the big beams to turn, I have instantaneous Direction Change.
NO STANDING WAVES
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. SEE BELOW
By using remote switches, there is No waiting for a rotator to turn, just every direction, every band, every time with the sites multiple antennas.
My area has major ice storms each year but the Rhombics survive
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 some power from the main lobe, but can also fill in other directions while transmitting. Although the upper elevation angles still bristle with lobes, they are generally all of low strength, and therefore hardly effect to antenna performance. And actually this is a plus for Hams, just like fishing (the more hooks in the water the better with hams sometime more lopes help), we are looking for contacts. In fact on 40 and 20 meters in daytime from my Kansas location high angles lobes help me make more north American stations, that is why the old ARRL Rhombic was stronger, then their newer beams in use today. see https://www.k0uo.com/post/hams-with-rhombic
The arrays are all modeld using NEC5 and HFTA (High Frequency Terrain Analysis) to evaluate the take of angle of the various antennas over real ground, then I do far field testing.
Rhombic vs. Yagi: Feature Comparison
Feature | Rhombic Antenna | Yagi-Uda Antenna |
Design Type | Traveling wave (non-resonant) | Resonant, parasitic array |
Gain | Up to ~18 dBi (with long legs) | 7–10 dBi typical (3–9 elements) |
Bandwidth | Very wide (multi-octave) | Narrow to moderate (depends on design) |
Efficiency | ~40–50% (terminated); up to ~90% re-entrant | >90% typical 70%- |
Directivity | High (unidirectional if terminated) | Very high (narrow beamwidth) |
Size & Footprint | Huge — hundreds of feet per leg | Compact — easily mounted on towers |
Polarization | Horizontal | Horizontal or vertical |
Installation Complexity | High — needs large land and tall supports | Moderate — rotatable and stackable |
Rotatability | Fixed direction | Rotatable |
Use Case | HF DXing, fixed-path comms | HF/VHF/UHF, rotatable beam for general use |
Performance Optimization
I now use a Re-entrant Rhombics, which are 90% efficient, by re-phasing the power back in the antenna, instead of heating up termination resistors.
It can be truthfully be said, that "a Rhombic antenna occupies more space per db of gain than any other antenna", however if you have the space you, will have the high RF gain. The Rhombic is a very high-gain antenna however it requires a lot of acres, and the efficiency when terminated is only about 50%. An alternate impedance-termination system, which was only used for a few large broadcast stations where input powers were above 50 kw, is called the re-entrant line termination. Clyde Haehnlen SK, developed the specifications for the Voice of America antenna system at the Bethany, OH Relay Station. That re-entrant Rhombic was 90% efficient by re-phasing the power instead of heating up termination resistors, in this system, the Rhombic is terminated in a transmission line, which in turn is coupled back to the input through the proper voltage-matching and phasing networks. Thus, the energy in the dissipation line is fed back to the antenna, so that considerably less than 50 percent of the energy is wasted. The old VOA Bethany site in Ohio had efficiency up to over 90%. This feeds-backs the wasted RF energy "In-Phase", back into the feeder end of the antenna. For any variation from the stubs frequency, the stub must be returned.
I am now the only station using re-entrant line termination equipment, which is re-phasing the power instead of heating up termination resistors.The Re-entrant Rhombic array is one of the highest forward gain HF antennas with its 90% efficiency, now with very high gain, and low noise receive characteristics.
Clyde provided me with design information for re-phasing a few years ago before his passing. However I am using the array on many ham bands 160 meters to 6 meters, which involved considerable engineering time to get it right, this was not needed by the VOA in the 1940s, they only used a few frequencies.
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 lobes are only 20 degrees wide.
ABOVE: Getting the hardware ready, 1000s of parts used
The first 4 poles with set by a cross country power line company. Most local power utility groups can only drill a 18" diameter hole and set 45 foot poles. After that I set them all myself
• Internal Gas Discharge Tubes, Capacitors and Resistors for an lightning arrester
• Can withstand multiple minor surges and shunts them to ground
• Bleeds off static charge collected from wind driven snow, rain and dust
Re-entrant Rhombic now used at K0UO
The Voice of America antenna system at the Bethany, OH Relay Station used re-entrant Rhombics, which was 90% efficient by re-phasing the power instead of heating up termination resistors, in this system. My antennas also uses the re-entrant system, the Rhombic is terminated in a transmission line, which in turn is coupled back to the input side, through the proper voltage-matching and phasing networks.
A drawback of rhombic antennas either due to load termination or presence of minor lobe due to open ends can be overcome by using arrays of rhombic antennas.
So, the rhombic antennas can be connected either serially or paralleled.
The combination of multiple antennas serves as an arrangement that provides combined directivity thereby increasing the radiation efficiency to 90% or more, which was 50% to 60% in case of a single antenna.
The FCC Monitoring Station in Ferndale, WA while working at nearby FAA facilities. They were out in the middle of nowhere and had a bunch of huge rhombics pointing in various directions. They had numerous receivers attached to them. Why did the FCC use rhombics?
FCC Ferndale closed in the 90s, and it's now just a huge undeveloped field.
Far Fields Testing
The K0UO amateur ham radio antenna range, and testing site has the use of over a thousand acres around the main antennas for far field measurements, using a portable tower or drone loaded with calibrated RF EME survey instruments (used for ham, DOD and Commercial), see the far field test page. https://www.k0uo.com/post/model-and-then-do-far-field-test
It is only after you actually measure the RF radiation pattern of what you simulate that you will gain a comprehensive understanding of what the antenna is truly doing at your specific location. This process involves several critical steps that are essential for accurate assessment and analysis.
I
A smaller 3wl per side, still has 16dBi with 28dB FB, my antennas are 4 to 6 waves on each side.
VK3MO Ian also had a stacked rhombic antenna with 8 wavelengths on a leg giving a total of 1340m of radiating wire. The upper rhombic is at 40M and the lower rhombic is at 21M. The rhombic had a gain of 23dBi at a take off angle of 5 degrees on 20M and is directed at New York. The rhombic was modelled using EZNEC and it has 3dB more gain than the 5/5/5/5 yagis Both the yagis and the rhombic have a take off angle of 5 degrees which allows a comparison between the two antennas in the direction of New York. Ian sees see the 3 dB advantage which validates the accuracy of the NEC antenna modelling software.
Traveling-Wave Antenna
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.
Operation: Rhombic and V beam antennas are true traveling wave antennas, meaning the current propagates along the wire and radiates as it goes, with little reflection at the ends. In contrast, the Yagi antenna uses a combination of driven and parasitic elements to shape and direct the radiation pattern, and its current distribution is a mix of forward and backward waves due to mutual coupling.
Directivity and Gain: Both can achieve high directivity,
Bandwidth: V beams and Rhombics have broader bandwidth, while Yagis are more frequency-specific.
Now that is Real GAIN
A tapered feed system as called an Exponential taper (specific mathematical taper shape) or“Klopfenstein taper” for a rhombic antenna is a method of impedance matching that gradually transitions the feed-line impedance to the rhombic antenna’s input impedance. Because rhombic antennas have very high, frequency-dependent impedances (often 600–800 Ω or more), a direct connection to a standard transmission line (50, 75, or 300 Ω) would cause severe mismatch and reflections.
A tapered feed (also called a tapered transmission line) is a progressively changing-impedance section of transmission line—usually open-wire or ladder-line—whose spacing or conductor size gradually increases from one end to the other.
The “taper” allows RF energy to smoothly transition from one impedance to another with minimal reflections, similar to a tapered waveguide or a transformer with many tiny steps.
A tapered feed:
Matches the line impedance to the antenna input
Smooths impedance variations over a wide bandwidth
Improves VSWR
Maintains the rhombic’s inherently broadband performance
Remember, "The Best antenna is one that is, In the Air and On the Air"!
Watch "KC9VKV HAM RADIO QSO - ROGER-W1VDE - THE LOST ART OF RHOMBICS!!! - JIM FERGUSSON/TRAX - RS 695" on YouTube
TO SEE the complete Blog list check @ https://www.k0uo.com/k0uo
"God is always the guess operator and copilot, open hearts, open minds, open doors for anyone to join in the QSO"
OVERVIEW of all the Steve Walz K0UO pages: The Rhombic antenna is a wide-band progressive traveling-wave (fast-wave) antenna, V-beams, Receive Directivity Factor (RDF) towers, VOA, W1AW, W6AM, Beverage traveling wave antenna, HF curtain, Broadcast tower, ham radio, balun for matching, IEEE, terminating resistor, E and H field, far field modeling, antenna measurements, NEC2 NEC4, k0uo, wire antennas, Curtain antennas, baluns, VOA sites, LPDA, W6AM, W7URA, Feed-lines, and 4KS Walz Airport at Kiowa, KS.
Welcome to K0UO.com, where we dive into the world of rhombic, curtain, and Vee Beam antennas at the Walz Kiowa, KS Airport 4KS. Explore the intricate world of rhombic antennas, Receive Directivity Factor (RDF) towers, Beverage traveling wave antennas, and so much more. Join us as we delve into the fascinating realm of antenna farming and ham radio technology.
The KØUO Rhombic Antenna Farm and Test Range: Home to the World's Largest amateur radio (ham), High Frequency (HF) Wire Antennas. Known as "Antenna University"
General Steve Walz
