Crossed field antenna
A disputed low-frequency antenna design with unsubstantiated efficiency claims.
The crossed field antenna (CFA) is a radio antenna designed for long and mediumwave broadcasting. Its inventors claimed it could match the efficiency of a conventional antenna while being only one-tenth the height, but experts in electromagnetics and antenna technology were highly skeptical because the idea lacked a solid theoretical foundation and credible experimental proof.
The antenna sits above a ground plane, which can be the earth itself. It has three main parts: a horizontal metal disc (the D-plate) raised above and insulated from the ground; a vertical hollow metal cylinder (the E-plate) mounted concentrically above the disc and insulated from it; and a metal lattice funnel (the extended conical section) that extends upward and outward from the top of the cylinder. The inventors described the antenna’s operating theory in their own literature.
Peer-reviewed journals generally did not accept papers on the CFA, which raised doubts about its performance. An independent study by Trainotti and Dorado, published by the IEEE, concluded that the CFA was no more efficient than a conventional antenna of the same height. Data from that report showed measured field values as much as 15 dB lower—only about 3% of what a theoretically perfect monopole would produce. The study also found that the D-plate always hurt performance; removing it improved the antenna, though it would no longer be a CFA. The report stated that the CFA was always slightly worse than a reference monopole in both gain and bandwidth, and that a simple monopole offered similar or better performance with an easier tuning system.
A small number of CFAs were built and operated in Egypt, with power levels from 1 kW to 100 kW, developed by the Egyptian state broadcaster ERTU. These had been running for over ten years. Other CFA projects in countries including Australia, Brazil, China, Germany, Italy, the Isle of Man, and the United Kingdom failed. The last commercial CFA was installed in 2003. In April 2004, at the DRM Consortium General Assembly in Hangzhou, China, a Chinese manufacturer called Zhongli, with help from Thales SA, fed a new CFA with 6 kW of DRM power for a demonstration, but the test results were not released.
- Patented
- 1986
- Patent holders
- F. M. Kabbary and M. C. Hately
- Claimed efficiency
- same as conventional antenna at one-tenth height
- Independent report conclusion
- no more efficient than a conventional antenna of the same height
- Measured field values
- up to 15 dB lower than a theoretical 100% efficient monopole
- Operating locations
- Egypt
- Power range
- 1 kW to 100 kW
Lore & Background
The crossed field antenna consists of three electrically active parts mounted above a ground plane: a horizontal metal disc (D-plate) raised above and insulated from the ground; a vertical hollow metal cylinder (E-plate) of smaller diameter, concentrically mounted above and insulated from the disc; and a metal lattice funnel (extended conical section) radiating outward from the top of the cylinder. The theory of its operation is described only in the inventors' own literature.
Peer-reviewed journals have generally not accepted papers on the CFA, casting doubt on its claims. An independent report published by the Institute of Electrical and Electronics Engineers found that the CFA was no more efficient than a conventional antenna of the same height, with measured field values up to 15 dB lower than a theoretical 100% efficient monopole. The report also stated that the D-plate always has a deleterious effect on performance, and that removing it improves performance, though the resulting antenna is not a CFA. The report concluded that the CFA's performance is always slightly worse than a reference monopole in gain and bandwidth, and that a simple monopole offers similar or better performance with an easier tuning system.
A handful of CFAs were installed in Egypt, operating at powers from 1 kW to 100 kW, developed by the engineering sector of the Egyptian state broadcaster. Many CFA projects in other countries—including Australia, Brazil, China, Germany, Italy, the Isle of Man, and the UK—failed. The last commercial CFA was installed in 2003. A demonstration in China in 2004 fed a CFA with 6 kW of DRM power, but results of that test are not available.
Reader's Guide
The crossed field antenna occupies a controversial place in antenna engineering. Patented in 1986, it promised a dramatic reduction in height for long and mediumwave broadcasting antennas—one-tenth the height of a conventional design—while maintaining equal efficiency. This claim was met with immediate incredulity from experts, as it appeared to contradict established electromagnetic theory. The lack of peer-reviewed publications supporting the CFA and the absence of independent experimental verification further eroded its credibility.
An independent IEEE-published report concluded that the CFA offered no efficiency advantage over a conventional monopole of the same height, and that its performance was actually slightly worse in gain and bandwidth. The report also noted that the D-plate, a key component of the design, always degraded performance. Despite these findings, a small number of CFAs were built and operated in Egypt, primarily by the state broadcaster, at powers up to 100 kW. Attempts to deploy the antenna in several other countries all failed, and the last commercial installation occurred in 2003.
The CFA's legacy is that of a highly disputed design whose theoretical and experimental foundations were never convincingly established. It remains a cautionary example in antenna engineering of the gap between bold claims and verifiable performance.
Did You Know?
- The crossed field antenna was patented in 1986 by F. M. Kabbary and M. C. Hately.
- The D-plate component always has a deleterious effect on the CFA's performance.
Frequently Asked Questions
What is the Crossed field antenna and what is it used for?
The Crossed field antenna (CFA) is a low-frequency radio antenna intended for longwave and mediumwave broadcasting. It consists of a horizontal insulated metal disc (the D-plate) positioned above a ground plane, paired with a vertical hollow metal cylinder (the E-plate), and was designed to radiate from a structure far shorter than a traditional mast.
Who patented the Crossed field antenna and when?
F. M. Kabbary and M. C. Hately filed the patent in 1986. The design was demonstrated at operating sites in Egypt, where the inventors promoted it as a practical alternative to tall conventional masts.
What was the main efficiency claim behind the CFA?
The inventors asserted that the antenna could deliver the same radiated efficiency as a full-height conventional monopole while standing at only one-tenth the height. This dramatic size reduction was the core selling point, though it was never backed by a rigorous theoretical derivation or peer-reviewed experimental data.
What did independent testing actually find?
An independent evaluation concluded the CFA showed no efficiency advantage over a conventional antenna of the same height. Measured field strengths came in up to 15 dB below the theoretical value for a perfectly efficient monopole, undermining the one-tenth-height equivalence claim.
Why is the Crossed field antenna considered controversial in the antenna community?
Electromagnetics experts have long regarded the CFA as a disputed design because its central efficiency promise lacks a sound theoretical basis and credible, reproducible measurements. It is generally catalogued as a speculative low-frequency antenna whose performance claims remain unsubstantiated.
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