Rhombic Arrays in WW2, Harnessing the Power to Win

The Rhombic Antenna won the war for the Allieds

World War II demanded reliable, long-distance communication systems to coordinate complex military operations across continents and oceans. Among the technologies that played a crucial role, rhombic antennas stood out for their exceptional performance in high-frequency (HF) radio communications. These antennas became a backbone for the Allied and Axis forces, enabling secure, high-power links and effective signals intelligence. This post explores how rhombic antennas shaped military communications during WWII and their continued use in the Cold War era.

Transpacific Telephone Company, Dixon CA: The rhombic antenna is seen from end aimed towards Hawaii, later a VOA west coast site

The Role of Rhombic Antennas in WWII Communications

Rhombic antennas gained prominence during WWII because of their ability to provide strong, directional radio signals over long distances. Their diamond-shaped wire configuration allowed for high gain and efficient skywave propagation, which was essential for maintaining communication across vast theaters of war.

Point-to-Point Communications

Military commands needed secure and reliable links between headquarters, theaters of operation, and allied forces. Rhombic antennas were deployed extensively for this purpose. For example:

• The U.S. Army Signal Corps used rhombics to establish high-power communication lines from North Africa to Europe.

• The Navy employed them to maintain links between Pacific island bases and mainland command centers like New York.

  
  

These antennas could handle kilowatts of power and offered gains between 9 and 15 dB over standard dipoles, making them ideal for long-haul transmissions.

Signals Intelligence and Intercept Stations

Rhombic arrays were also critical for intercepting enemy communications. Field stations often erected clusters of six or more rhombic antennas to cover wide frequency ranges and directions. Notable examples include:

• Pacific theater stations built by Australian forces, which used rhombics to monitor Japanese transmissions.

• Remote U.S. Army and Navy stations on Pacific islands, where rhombics provided reliable skywave paths for intelligence gathering.

  
  

Veterans recount stories of local populations sometimes stealing copper wire from these antennas, which led to negotiations to protect these vital communication assets.

Military Manuals and Field Deployment

The U.S. War Department recognized the importance of rhombic antennas and issued TM11-2611, a detailed manual and kit for field deployment. This manual covered:

• Construction techniques for rapid assembly.

• Proper termination methods to maximize efficiency.

• Guidelines for use in various environments.

  
  

This standardization allowed military engineers to deploy rhombic arrays quickly and effectively in diverse locations.

U.S. Army at a Rhombic site

Efficiency and Scale of Rhombic Arrays

Rhombic antennas required significant space, often occupying acres per array. Despite this, their efficiency made the trade-off worthwhile:

• Large terminated rhombics could handle high power levels without significant signal loss.

• Their directional gain made them superior to many other antenna types for fixed HF links.

• Ham radio operators later dubbed them "the antenna that won WWII for the West" due to their unbeatable long-distance performance.

  
  

While rhombics complemented other antenna systems, they dominated fixed point-to-point HF communications where space was available.

Rhombic Antennas After WWII and During the Cold War

Rhombic antennas did not disappear after WWII. They remained in heavy use through the Cold War for signals intelligence, diplomatic communications, and military links. However, newer antenna types like log-periodic and curtain arrays began to replace them in broadcasting applications.

U.S. Navy Installations

Naval Radio Station Wahiawa in Pearl Harbor, Hawaii, and Kodiak Island, AK are prime examples of Cold War rhombic use. From the early 1950s, they featured large rhombic fields for:

• Signals intelligence operations, like NAMCOMSTA

• Long-haul communication links to Guam and the U.S. mainland.

  
  

Some of these rhombic paths remained active into the 1990s, such as those connecting to Guantanamo Bay, before being decommissioned.

RHOMBIC ARRAY SITE

Army and Air Force Use

The U.S. Army and Air Force continued to rely on rhombic antennas for secure, long-distance HF communications. Their ability to maintain reliable skywave paths made them valuable for:

• Forward operating bases.

• Remote command posts.

• Intelligence gathering stations.

  
  

Even as technology advanced, rhombics provided a dependable option where space and power were available.

Voice of America VOA

VOA Dixon, CA site

The VOA Dixon Relay Station goes back to WW2. Though not as famous as Bethany, Ohio or Greenville, North Carolina, it played a roll in the VOA success story. Prior to the inception of VOA, there were a number of shortwave broadcast stations in the United States of America operated by the National Broadcasting Company, Columbia Broadcasting System, General Electric, Westinghouse, Associated Broadcasters, Crosley Radio Corporation, Worldwide Broadcasting Foundation and the WCAU Broadcasting Company. Prior to World War II, The United States Government contracted with some of these companies for broadcasting government programming.

With the outbreak of World War II, the government opened a new agency, the Office of War Information (OWI) the genesis of the Voice of America. Following Pearl Harbor, the federal government decided to go forward with its own shortwave broadcast under the Voice of America program. As part of process they acquired interest in the broadcasting facilities at Delano and Dixon, California in the early mid 1940’s to transmit programs to the Far East and the Pacific Rim.

A photo of a large balun from "The VOA Dixon Relay Station" now in use at the historic K0UO Rhombic farm in Kansas also a smaller 600 ohm balun used at DOD sites in WW2, with smaller baluns now used for ham radio

The K0UO antenna farm is proudly using parts from many legendary stations, to continues the tradition they started with the big arrays, like the VOR (Voice of America), Armed Forces Radio, Navy, Army/AF, DOD, W6AM Don Wallace, BBC, Art Bell W6OBB, W7YRV Roy Callison, and others. So symbolically those large historic stations are still, "On the Air Daily" by K0UO using an extensive array of towers and antennas.

Practical Lessons from Rhombic Antenna Deployment

The extensive use of rhombic antennas during WWII and the Cold War offers several practical insights:

• Space matters: Rhombics require large areas, so site selection must consider available land.

• Power handling: Their ability to manage kilowatt-level transmissions makes them suitable for high-power applications.

• Directional gain: The diamond shape focuses energy, improving signal strength and reducing interference.

• Maintenance challenges: Copper wire theft and environmental wear require ongoing protection and upkeep.

• Standardized manuals: Clear construction and operation guidelines enable rapid deployment and consistent performance.

  
  

These lessons remain relevant for modern HF communication systems in military and civilian contexts.

RCA Rocky Point, NY

Today the K0UO Rhombic Farm in Kansas is now using parts and equipment from these large sites daily.

https://www.k0uo.com/post/the-king-of-wire-antennas-is-a-rhombic

K0UO Rhombic Loge

Building the old HF sites

https://forums.qrz.com/index.php?threads/the-ultimate-dx-ssb-receiving-station-in-1940.807379/