LFR and other systems that would follow were (a) specifically developed as large-scale programs with numerous sites, (b) were widely adopted by civilian and military aviation and (c) utilized for decades. All were used internationally. Here are the dates they were developed and implemented:
- LFR (Low Frequency Radio Range): developed in 1926, implemented 1928, last used in 1971 US, by the mid-1980’s elsewhere. 4-course aural system.
- Lorenz Beam: developed in 1932, commercially available 1934, last used in 1960. Single beam aural system.
- Elektra-Sonnen & Consol: developed and implemented 1940, last used in 1991. Rotating multi-beam aural system.
- Gee: developed and implemented in 1942, last used in 1970. First hyperbolic system.
- LORAN (Long Range Navigation): developed in 1941 implemented 1942, discontinued by 2015. The most widespread hyperbolic navigation system used. May be revived as a backup to GPS.
- VAR (Visual Aural Radio Range): developed in 1937, implemented 1944, last used 1960’s US and the 1980’s elsewhere. 4-course system.
- Decca: developed in 1942, implemented 1944, last used 2001. An additional hyperbolic system.
- VOR (Very High Frequency Omnidirectional Radio Range): developed 1937, implemented 1946. Visual system, still in widespread use.
- Starting in the 1980’s when GPS first became available for civilian use, Satellite Navigation Systems (SATNAV) would rise to dominance by the start of the 21st century.
By this account, it appears that LFR had a six-year head start ahead of the Lorenz Beam which took off in the 30’s and over a decade on the other systems that would propagate in the 1940’s. Of these only Lorenz, VAR and VOR also provided immediate “real time” guidance along a specific airway or course with minimal work for the pilot. The rest only established a bearing or fix at one point in time, which the pilot would then need to analyze further to determine any necessary course correction.
LFR also already had at least 7 operational stations in the US by the time England's Orfordness Beacon went on-air July 1929. It used a similar concept to the Telefunken system described above, as well as an experimental 1920 maritime beacon developed by Marconi, where a rotating loop antenna was used instead of a fixed array to smoothly sweep the directional signal after the omnidirectional timing pulse. Only one sister station was built at Farnborough before it was surpassed by other efforts.
The basic principles of VAR and VOR, the successors to LFR, are covered on the Its Fate Page. A quick overview of the other systems is as follows:
Germany’s Lorenz Beam was, in essence, a narrow single aural “beam” that used two slightly overlapping 33.33Mhz signals, one of dots and the other of dashes, that merged to create an on-course "equisignal" tone. The signals were generated by a single transmitter that continuously broadcasted on a center dipole antenna and used a cam switch to quickly alternate the signal to two adjacent dot and dash dipoles that formed highly directional lobes. It was used successfully by the 1930’s as an early Instrument Landing System and for long range navigation (Australia preferred this system over LFR). During the “Battle of the Beams” the “Knickebein” bombing aid intersected two such beams over targets in England.
The Elektra-Sonnen system (simply “Sonne,” German for “sun) was implemented by Germany at the start of World War II. The British also surreptitiously used it and named it Consol (Latin for “by the sun”). It combined the Lorenz Beam and Orfordness concepts by radiating 18 rotating equisignals that, after the omnidirectional timing pulse and station ID was sent, would each then sweep across a fixed pie-shaped sector roughly 15° wide over a 30 second period. These sectors were plotted on charts and arranged in two equal opposed “fans” about 135° wide on each side of the station. They were formed by a continuous 250-350khz signal from a center antenna, flanked by two more spaced 3 wavelengths away (about 1.8 miles). The signal alternated between these outer antennae at 1-second intervals to create two heart-shaped “cardioid” dot and dash patterns. Additionally, their signal phase was adjusted to create deep “ripples” (e.g. lobes formed by wave interference) that counterrotated around the edges of both patterns. These interacted to form the many moving equisignals. Technically, these were condensed hyperbolic waveforms between the 3 antennae but from miles away these patterns appeared to radiate from a single point like the rays of the Sun, hence the system’s name.
After using a radio compass or other means to determine the sector the aircraft was likely in, the number of dots heard after the timing pulse would be counted until the equisignal emerged which then faded into dashes. A chart or table would convert this count into a bearing accurate to within ½° to ¼°. It took a few minutes to assess the 2 to 3 counts needed to most accurately derive a bearing, but like LFR only a simple AM receiver was needed. Its simplicity (e.g. just count the dots) and 1,000-mile range kept it in service in for 50 years.
Hyperbolic Navigation also emerged during the war. It used the time between an initial signal pulse sent by a “master” station that was responded to by another pulse from two or more or “slave” stations located hundreds of miles apart along a defined “chain,” after a short time delay, to determine location. Mathematically, a line that has a constant amount of signal delay between two points forms a hyperbola, hence the origin of the term. Dozens of such “lines of position” were plotted on aerial and marine navigation charts for each chain, typically in 100 microsecond (ms) increments. By reading the time difference between the master and at least two slave stations on a dial or cathode ray tube (or from another chain) the user could determine which two lines of position they were on and the intersection marked their location.
The British developed Gee as the first hyperbolic system for its bombing operations which operated at 20-90 Mhz and had a range of a few hundred miles. This inspired the US to shortly follow with LORAN to extend radio navigation for its Atlantic convoys. It operated at a lower frequency of 1.75 to 1.95 Mhz so it could use skywave propagation, had a roughly a thousand-mile range, was fairly easy to use and was accurate to within a few miles. Decca was a similar hyperbolic system (also developed in the US but first implemented in Britain) but used the phase comparison of low frequency waves between 70 and 129Khz to determine distance. In late 1950’s “LORAN C” emerged that used both timing and signal phase, like Decca, to provide accuracy to a few hundred yards, but it initially used expensive 100lb receivers. However, the now cheaper, down-market “LORAN A” receivers became common globally and by the 1970’s microelectronics made LORAN C units small and affordable . Decca further evolved into Omega, a US military only global network of 8 stations that served from 1971 to 1997 prior to GPS.
QUESTION 2:
Did the Ford Motor Company really invent the Low Frequency Radio Range? How was it developed?
Yes, the Ford Motor Company is indeed the official inventor as is made abundantly clear by US Patent #1,937,876 filed in Ford’s name in 1928. The Ford Museum still retains an original 1927 transmitter building and other components in its collection. However, like many inventions in history, there was a long road of others who developed and refined its key concepts and prototypes, and in the end, Ford and the US National Bureau of Standards would have different accounts of its creation.
In 1907, just four years after the Wright Brother’s took flight, German engineer Otto Scheller (who would go on to develop 70+ patents for the Lorenz Company) conceived a radio beacon that used 4 vertical antennae to create two overlapping figure-eight signal patterns. One signal was a dot (the Morse letter “E”) and the other a dash (the Morse “T”) that interlocked to form an on-course signal along 4 beam lines. This was the core principle of the Low Frequency Radio Range. A patent for the system was filed in 1907. In 1916 he had the foresight to update the patent to include a radio goniometer to adjust the beams. A demonstration station was set up in 1917 using the “A” and “N” letters but as with the Kompass Sender above there simply wasn’t yet a fleet of radio equipped planes to take advantage of it. In the economic devastation and severe sanctions that followed Germany’s defeat in the First World War there was little interest in pursuing it further. The idea was simply ahead of its time.
Some sources credit the United States Bureau of Standards for the invention of the LFR. Certainly, between 1920 and 1923 Bureau scientists Percival Lowell, Francis Dunmore and Francis Engel, developed a “directive type” radio beacon that used two compact loop antennae to create a four-course system using the letters “A” and “T”. Sources vary as to the extent that they were aware of Scheller’s design – but vertical antennae were not used and the system lacked a goniometer. The antennae crossed at 45° to accentuate two of the beams along a main course that was assessed. A station was successfully tested in Washington DC by land and sea in May 1921, and in the air by the US Army Air Service and Signal Corps in 1923 at McCook Field in Dayton, OH (this field was replaced by Wright Field in 1927, now Wright/Patterson Air Force Base). However, its rudimentary spark gap transmitter required that a plane drag a weighted 200’ antenna behind the aircraft to receive the signals. It was a promising experiment but it was not quite ready for practical commercial use. For reasons unknown, the Bureau’s funding for further development was cut off in 1923.
Although the Bureau was temporarily out of the picture, the US Army Air Service and Signal Corps continued their experiments and were apparently aware of Scheller’s patent. An improved beacon was set up in Dayton by 1924. By 1925 at Monmouth, IL, General Superintendent of the US Airmail Service Carl Egge and Edward Warner of M.I.T. gained permission to set up an “Equi-Signal Radio Beacon.” It was built under supervision of the Radio Laboratory at McCook Field which was involved in the 1923 test. It used the latest vacuum tube radios, interlocking “A” and “N” signals and first employed a radio goniometer tested by the Signal Corps to adjust the beams – a key ability of future stations. A later addition was a three-light indicator to show if the pilot was on, right or left of course.
A September 12, 1925 Air Service News Letter describes these developments and stated “perfected, the Radio Beacon is bound to be of inestimable value.” Pilots stated it was a “very simple matter to remain on course.” It was another step closer, but still required the use of trailing wiring antennae and its cost of $6,000 per plane, or $89,000 in 2020 dollars, was prohibitive. Egge faced considerable internal headwinds. At the outset, Egge’s superiors told him to avoid “experiments that do not lead to anywhere,” and a later internal review found “little of importance was being done.” Egge was accused of misappropriation of funds and had to resign. The project was terminated but not before a paper was published - as such, many in the industry were aware.
The stage was set in 1926 when Congress passed the Air Commerce Act which established the US Government’s role in regulating but also furthering development of aviation by its creation of the Department of Commerce’s Aeronautics Branch. Both public and private sector aviation R&D boomed. At this stage there were published accounts and papers on the Monmouth Station, the Army Air Corps tests, the Bureau’s initial “directive” beacon as well as Scheller’s original patent – it would be difficult for anyone to now claim that they had a fully original ideal for LFR. Ford’s first range station would be finished later that year and in July 1926, the Bureau of Standards was given an expansive budget and a mission to find a suitable radio navigation system for the Department of Commerce. Events transpired quickly over the next few years:
- In 1926, Ford hired Eugene S. Donavan, a young civilian engineer who was part of the Army Signal Corps Dayton team that continued work after the McCook Field experiments and that oversaw the Monmouth station. The Army would be present for later Ford tests. When the Dearborn station was finished and licensed by October 1926 it, unsurprisingly, contained nearly identical improvements, e.g. vacuum tube transmitters, the goniometer, etc. It also added a more robust automatic key and the ability to handle Morse communication with the pilot by temporarily suspending the signals, another key feature of LFR. The subsequent patent stressed its objective was to create an “inexpensive” setup: Ford engineers “borrowed” receivers from the quickly evolving radio technology market and found the simplest, least costly units and antennae that could easily fit on board – the final challenges to be solved. The stations vertical masts were spread 90° apart to create 4 equal courses, similar to Scheller’s original concept. It was recognizable as a range station.
- By February 1927, when Ford started to use its system to ferry auto parts through snowstorms, LFR ceased being an experiment and first became a commercially practicable system that was proven to work under adverse conditions. Ford operated this private LFR network of 3 stations until 1934.
- A February 27, 1927 New York Times article reported on the experimental beacons at Ford Airport that were “undertaken with cooperation with the Department of Commerce and Army Air Corps and several radio companies from which receiving sets were borrowed.” Department officials were “encouraged” by “splendid reception” along a 142-mile test course that pilots flew “quite easily.” It appears then that there quite a bit collaboration across the field between government and private industry, a likely exchange of ideas, and certainly wide awareness of Ford’s progress. The only party not specifically mentioned was the Bureau of Standards.
- After a 3-year absence, the Bureau was back in the game on July 1926 as described above. Construction began immediately on its College Park, MD station which started field experiments in December 1926, about three months after Ford had constructed its Dearborn station. College Park was officially “inaugurated” in May 1927. In December 1927 (10 months after the New York Times article above) the Bureau began the first demonstration runs at Hadley Field NJ, and Cleveland, OH under the direction of Section Chief D.H. Dellinger (incidentally, some using Ford Trimotors). The first three stations entered service in 1928. These new stations, the first in the US LFR network, strongly resembled Ford’s 1926 system and patent and were not similar to the Bureau’s 1923 prototype as seen above. The vertical loop antennae, vacuum tube transmitters, and other improvements they utilized were all first used by Ford and the Army. Of additional note is that Ford decided to file its patent application in May 1928.
- This is where the stories diverge: in reviewing the Bureau's later accounts and Air Commerce Bulletins, the Bureau credited itself with the creation of LFR . The Bureau’s 1929 treatise “Development of The Visual Airway Beacons," co-authored by Dellinger, which was intended to give a “general” history of the system, stated that it was the “result” of the Bureau’s research from 1926 to 1929 and that it was the “outgrowth of a development undertaken by the Bureau of Standards in 1920.” Remarkably, neither Ford’s accomplishment and patent application, or the Monmouth station, were mentioned in these sources. A passing reference is made to a “German” patent and the Army's work with the goniometer. This paper also discussed two Bureau innovations developed by Henry Diamond and Francis Dunmore, the visual reed indicator (discussed on the It’s Use page) and an experimental 12-Course version of LFR.
- So, if LFR was indeed the “result” of the Bureau’s work, one would think that it would have had a solid case to appeals Ford’s patent: however, as Ford’s patent held, it appears that any challenges to it were unsuccessful. Ford’s patent was granted in 1933 – interestingly after a 5 year delay. Ultimately, the Bureau would file patent No 2,172,365 for the improved Adcock type range, but that wouldn’t be until 1933 (granted 1939).
- In 1934, the Federal Communication Commission (FCC) summoned Ford Motor’s William Gassett to a hearing, demanding to know why Ford was in the business of operating radio navigation aids. The FCC reasoned that the beacons, like lighthouses, should be the exclusive province of government and the Department of Commerce. The end result was that Ford was denied renewal of its radio licenses for its three range stations. Gassett, dejected, suggested that the Ford charge royalties on its patent – this demonstrates that Ford believed that the Department of Commerce’s range stations were using technology covered by its patent. Indeed, a 1946 Ford biography noted “the present ‘radio range’ is merely a refinement of the system originally designed by Ford Engineers.” Ford declined, stating his desire to support commercial aviation and that Ford was an automobile and not a radio beacon manufacturer. Perhaps Ford chose this action to settle the dispute, either way its patent stood.
- A final coda: the incoming Roosevelt administration terminated the Bureau's funding for further research on March 4, 1933 (Inauguration Day) for unspecified reasons. Further development on the 12-course version and visual indicators died with this decision, quite possibly to aviation's immediate loss: LFR would remain a 4 course, aural system. One source indicated “interdepartmental bickering” was a factor in the demise of these innovations.
Dated photographs and radio license in Ford Museum, and the excellent chronologies in Bonfires to Beacons and Beyond the Model T (see Resources) helped round out much of the timeline here and at top of the of the What it Was page.
The bottom line: Ford picked up where Monmouth and the Army Signal Corps efforts left off which appear to have been more directly inspired by Scheller’s Patent. Donavan’s hire and the Army’s presence at subsequent Ford tests would seem to imply a close working relationship here. Both of their developments came after the Bureau’s nascent 1923 station, and before its mature 1928 stations which incorporated all of these enhancements that made LFR truly workable. Certainly, there was wide collaboration across the field and new and old ideas circulated between groups. Arguably, many of the more logical improvements (e.g. vacuum tube radios) could have been intuited separately by Ford and the Bureau. But for whatever commonalties these factors led to in their final designs, Ford was the first to build a practical physical station that ordinary aircraft could use, the first to use it for a commercial purpose and, perhaps most importantly, it was first to the Patent Office. Afterwards, Ford clearly believed the Bureau and the Department of Commerce was using its innovations.
It’s not clear why the Bureau and later Department of Commerce accounts couldn't concede this. Even many modern accounts omit this history, likely as they simply relied on the Bureau’s records as gospel. The Bureau’s papers were instead solely focused instead on its successes and improvements (e.g. the 12-course and visual indicators) possibly done to work around the patent. Was this just a private versus public sector rivalry which led to the FCC’s ultimate push to get Ford out of the beacon business? Did the Bureau’s academic scientists, stymied by earlier funding cuts, have difficulty giving Ford’s well-resourced “commercial” engineers (and others) any credit for apparently making “their” earlier concept practical? On the other hand, the story of large corporations using the patent process to “appropriate” the honest work of others isn’t entirely unheard of. This is notwithstanding the fact that both parties heavily relied on prior innovations. A century later, it may be impossible to exactly ascertain what transpired, but it’s clear that Ford and the Bureau didn’t see events eye-to-eye. If anyone has any additional info that can clarify this history, please reach out to me!
Regardless, in the end, it was the US Government that awarded the patent to Ford and the US LFR network came to be only after Ford’s successful 1926/27 stations. Making the Low Frequency Range a practical reality was likely Ford’s most important contribution to aviation, outliving its famed Trimotor and the entire aviation division which shut down by 1933 due to the Depression. But, as with many inventions, Ford’s patent was rooted on prior efforts: every step that led to it heavily borrowed from previous ones. Ford’s role should also not discredit the Bureau’s many accomplished minds - Dellinger and Diamond would become luminaries in their field. College Park became the birthplace of radio voice communication in aviation, standardized LFR station design and would continue to make important refinements to the system. Renamed the National Institute of Standards and Technology (NIST) in 1988, the Bureau had gone on to develop the first Instrument Landing System, the atomic clock fundamental to GPS, and countless other innovations. Finally, it must be remembered that system’s foundation was built with German (Scheller), Italian (Bellini-Tosi) and British (Adcock) contributions as described elsewhere.
After nearly 30 years, the 1954 Civil Aviation Authority “Pilot’s Radio Handbook” would acknowledge Ford’s role and patent.
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