The KING of Wire Arrays, Rhombic
- skylarkcolo
- Mar 2, 2019
- 11 min read
Updated: 2 days ago
K0UO is working on the "Lost Art of Rhombics" with 4 of these large wire antennas at the Kansas QTH beaming at the 8 main DX areas, and phasing for more steering.
The "KING of Wire Antennas" refers to the Rhombic type. Each antenna is designed for 40 meters and above, stretching over 1200 feet from end to end, covering 6 to 7 acres, and mounted on 80 to 100-foot wooden poles. The Front to Back ratio is like a brick wall, potentially +45dB or more. This results in each side being 4 to 6 wavelengths long, totaling 16 to 24 wavelengths for 40 meters. These are the largest 40-meter Rhombic antennas currently in 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 improvement compared to the full-size 40-meter wire 2-element beam at a height of 100 feet is absolutely astonishing, Gain before Amplification. The QTH also features two extensive 1200' Vee-beams mounted on 75-100 foot wooden poles.
Some 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).
K0UO is best known as an antenna Experimenter, and Ragchewer 1st and DXer for fun! See the qrz.com website and lookup the K0UO call for more info.
A Rhombic Antenna = The highest development of a long-wire antenna.
The K0UO site uses repurposed equipment from W6AM's old station, W7YRV, Voice of America, The BBC and other legendary stations.
OVERVIEW
An ideal HF antenna option for commercial and maritime shore stations, military applications, broadcasting, frequency-agile needs, high-speed trading, diplomatic communications, EME, and amateur ham radio.
The 100 foot wood poles are almost 36" wide at the base, on the main east-west continental US antenna four of the insulators are from the famous W6AM rhombic farm, which was located in Southern California http://www.qsl.net/ne6i/w6am/antennas.html
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 miles of wire in the Air, “The RF Gotta-Go-Somewhere”. Note a full size 2 element 40 meter phased wire beam at 100 ft is used for a reference antenna.
It can truthfully be said that "a Rhombic antenna occupies more space per dB of gain than any other antenna!" The Rhombic is a very high-gain antenna, but it requires a lot of space, and its efficiency when terminated is only about 50%. However, when using the Re-entrant line power recirculating system, its efficiency significantly increases to around 90% by properly matching impedance and phasing to recombine the power, and by replacing the termination resistor.. The improvement in efficiency is achieved not only through better impedance matching but also by replacing the conventional termination resistor with a more effective solution. This adjustment allows for a greater percentage of the input power to be radiated as useful signal rather than being dissipated as heat, which is a common issue with traditional termination methods. In conclusion, while the Rhombic antenna is indeed a space-consuming design that may initially seem inefficient, the integration of advanced systems like the Re-entrant line power recirculating system can dramatically enhance its performance. This makes the Rhombic antenna a more viable option for applications that demand high gain and efficiency, despite its spatial requirements. As antenna technology continues to evolve, the potential for further improvements in designs like the Rhombic becomes increasingly promising, allowing for better performance in various communication scenarios.
I am now using the biggest HF Re-entrant Rhombic arrays, and they are the highest forward gain HF antennas with its 90% efficiency, with very forward high gain, and low noise receive characteristics. So, the Rhombic wire arrays can beat the massive stacked HF beam arrays that I had up before.
All long Traveling wave antennas are known for fantastic Improvements in the reduction of QSB fading, for both transmit or receive.
It is like Diversity receive, theses large arrays cover a lot of area (acres).
Most of my antennas 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.
Open-wire feed lines are attached to each end of the antennas, converging at a central point in the middle. This configuration allows for the integration of a termination resistor or a balun, which alters the direction. The antennas also perform very well in the "Bi-direction" mode. Most of the rhombic antenna's performance limitations stem from the high levels of spurious lobes and its low efficiency (50%), particularly over typical soil. The rhombic ranks poorly in terms of gain-per-acre among high gain HF antenna arrays. However, it offers the significant advantage of operating over a wide range of frequencies with a flat SWR and high gain, which a basic monoband yagi cannot achieve. Additionally, the rhombic is a straightforward antenna, requiring only four supports (three for the Vee beam and one for inverted Vee variations).
Some of these aspects can be quite beneficial for the everyday use of antennas in amateur radio service. It's important to remember that amateurs are not point-to-point shortwave broadcasters, military, or wire services; they just want to make QSOs! Additionally, most amateur radio operators don't have the budget to spend tens of thousands of dollars on tall towers and stacked monoband beams, nor the capability to climb and maintain such structures. Rhombic antennas represented the pinnacle of antenna design during the Golden Age of Wireless. However, constructing one required a large area and many tall telephone poles, as their dimensions are several times the wavelength. For most amateurs, the advantage is that there are no large monoband antennas to maintain or rotators to repair, and rhombics offer instantaneous direction and band switching. They can typically be installed at a very low cost if you have trees to hang them from; all you need is a lot of wire and time! Furthermore, the key concept of traveling-wave antennas is the absence of standing waves, meaning that the current and voltage levels are consistent along the antenna conductors. Therefore, the rhombic antenna offers the significant advantage of operating over a wide range of frequencies with flat SWR and high gain.
The Voice of America antenna system at the Bethany, OH Relay Station utilized re-entrant Rhombics, achieving 90% efficiency by re-phasing the power rather than dissipating it in termination resistors. Similarly, my antennas employ the re-entrant system, where the Rhombic is terminated in a transmission line that is then coupled back to the input through appropriate voltage-matching and phasing networks.
The K0UO Rhombic Farm is 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.
Traveling wave antenna has no SWR: 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.
see traveling wave below
I model all my antennas 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.
The large wire antennas can build up static, dry wind and dust storms make the antennas crackled with powerful static electricity. All of the antennas are shunted to ground all the time.
In the 1930s dust bowl days out here in Kansas, there was so much static electricity that built up between the ground, and airborne dust, that blue flames leapt from barbed wire fences, and well-wishers shaking hands could generate a spark so powerful it could knock them to the ground. Since static electricity could short out engines, and car radios, motorists driving through dust storms dragged chains from the back of their automobiles to ground their cars.
Once the dust particles reach a certain density the level of charge shot up.
Think of dust particles as little globes, each with two hemispheres. When the particles become polarized, one hemisphere becomes positive and the other hemisphere becomes negative. Since positive charges attract negative charges, a negatively charged hemisphere on one dust particle can attract a positively charged hemisphere on another dust particle.y When they meet, they neutralize by transferring the electron from the negatively charged hemisphere to the positively charged hemisphere.
Think about this when building an antenna: The Maximum usable frequency (MUF) is important for determining the best HF frequency to use in communicating between two locations and most amateur radio operators understand it. But for general amateur radio work, maximum usable angle (MUA) is probably more important than maximum usable frequency. Maximum usable angle focuses on band availability, the types of antennas needed to take advantage of band openings, and the skip distances that can be expected. The maximum usable frequency equation for communicating is Fm = Fo / (sin Ae) . The main lobe elevation angle depends on the configuration of the transmitting antenna. When these antennas were designed, MUA to DX locations from K0UO's KS QTH had to be the main part of the that design. Using the ACE HF Pro software by Long Wave, allows K0UO to analyze the entire HF spectrum at any time on any band, from K0UO's QTH to any location.
A nice youtube overview of rhombic https://youtu.be/fmWlOisao-I
The Big project for 2020 was increasing the efficiency of the rhombic: 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 Haehnle n SK, developed the specifications for the Voice of America antenna system at the Bethany (Ohio) Relay Station that 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, some of 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%, Clyde provided K0UO with design information for re-phasing a few years ago. The normally displaced terminated power is returned to the input line by properly phasing and adjusted to the Voltage magnitude through the use of stub line of proper values and space a long the return line. Impedance of the line is corrected in a like manner in some cases combined with one of the re-entrant stub lines, all stubs are shortened and grounded at the midpoint for lightning protection. This feedbacks 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 retuned.
So how do you get higher efficincy from a rhombic? A parasitic or active reflector could be used or couple an out of phased reflector depending on the situation. Recirculating the power from the termination resistor in these phased coupled antennas could add about 3db power for the antenna to radiate while increasing the efficiency.
VOA antenna info, Clyde Haehnle, developed the specifications for the Voice of America antenna system at the Bethany (Ohio) Relay Station that Rhombic was 90% efficient by re-phasing the power instead of heating up termination resistors, https://www.youtube.com/watch?v=3w_ZXRJol_4
TO SEE the complete Blog list check @ https://www.k0uo.com/k0uo
Steve Walz
The K0UO antenna test range site makes use of the 4KS Walz airport and its surrounding area as a practical learning environment for STEM (Scientific, Technical, Engineering, & Mathematics) antenna projects in a real-world outdoor setting. If your group has a university aerospace or antenna research STEM program, please let me know.
Welcome to the K0UO Ham Radio Station, home a large antenna site and test range, spanning many acres. Featuring miles of antennas and tower structures—including FCC-registered reaching up to 195 feet—our facility is a dream destination for serious contester and big gun operators. With numerous -foot wooden power-line poles, concrete silos, and portable mobile towers, the K0UO Rhombic Farm stands out for its significant height and capabilities. Registered under Antenna Structure Registration number 1216715, our station is recognized in the FCC public file, credibility and verification that sets us apart from other so-called big gun ham stations. The station and antenna farm uses very complex highly engineered arrays.
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