©2004-2022 F. Dörenberg, unless stated otherwise. All rights reserved worldwide. No part of this publication may be used without permission from the author.

Latest page updates: June 2022 (made into separate page; added ref. 230R8, 245B-245D)

Previous updates: January 2022 (inserted section on bombing); December 2021 (added ref. 230Q5, 230Q6, 230R13); 28 May 2021 (note: now about 800 literature references provided on the WW2 Rad Nav pages, almost all downloadable!); April 2020 (started complete overhaul & expansion of this page).

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In 1909, the Prussian Building Authority considered the quenched-spark transmitter to be sufficiently mature, and abandoned mobile radio direction-finding receivers. Instead, it decided to pursue a directional radio beacon on land, and a relatively simple standard receiver ship-board. Mid-1909, it was proposed to build two transmitter stations on Müggelsee Lake (about 20 km southeast of the city center of Berlin), ref.187A5:

  • A Bellini-Tosi system on the site of the Royal Inland Fisheries Institute (D: "Königliches Institut für Binnenfischerei") at Friedrichshagen. This comprised two orthogonal antenna pairs, and an Artom radio-goniometer to rotate the directivity of the antenna system. It possibly was as large as 36 m tall (≈120 ft), and 127 m wide (≈415 ft) at the base (p. 351 in ref. 186L).
  • A directional transmitting station to the east of there, on higher terrain outside the nearby village of Rahnsdorf. The antenna system was to comprise 32 masts that supported 16 dipole antennas in a star configuration. The dipoles were to be aligned with standard compass directions. The dipoles were to be energized in sequence, to obtain a (stepwise) electro-mechanically rotating radio beam - the world's first rotating radio navigation beacon! Per ref. 2A, the switching mechanism was motorized. A separate Morse-code-like sequence of "dots" and "dashes" was to be transmitted by each dipole. Most likely, this was exactly the same scheme as used during follow-on tests around 1912 at Cape Arkona (see further below). The receiver station determined the direction from which the transmitted signals arrived ( = Angle of Arrival, AoA), based on identifying the dipole from which the smallest signal was received.


Fig. 46: Map of Müggelsee (ca. 4.3x2.6 km / 2.7x1.6 miles) with Friedrichshagen and Rahnsdorf

(source: "Pharus-Plan Berlin-Oberspree 1919" tourist map)

During 1912-1913, the offices and labs of the Maritime Navigation Markers Test Site (D: "Seezeichenversuchsfeld") of the Maritime Navigation Markers Office (D: "Seezeichenausschuss") of the Ministry of Public Works were built next to the Fisheries Institute (ref. 187A2-187A3, also right-hand image in Fig. 46 above), and their facilities moved there from Berlin-Tiergarten.

The mention of a Bellini-Tosi (B-T) system for transmitting is somewhat unusual. Such systems (two crossing loop antennas with radio goniometer coupling) were primarily used as DF receiving stations, not transmitter stations. Also, a 3-mast B-T would have been non-standard. Per ref. 187A7, only one small 16-dipole transmitting station was built on Müggelsee Lake. Per ref. 187C1-187C3 (Telefunken, 1912), there were actually two transmitter stations, one of which had a rather large 16-dipole antenna system: a diameter of 200 m (≈660 ft). Telegraphy engineer Franz Kiebitz (at that time working at the Imperial Postal Administration) participated in the receiving tests from a boat on the lake.

Per ref. 187A5, two medium-wave frequencies were proposed to be used: around 2.4 and 3 MHz (wavelength of 125 and 100 m, respectively). This coulds explain the simultaneous proposal for two transmitter stations. These frequencies were roughly the demonstrated practical upper limit of spark transmitters at the time. However, these two frequencies are actually too close together to warrant two separate installations, or even two test series. Per ref. 187A7, the actual antenna system was small. However, per ref. 187C1-187C3 (Telefunken, 1912), the actual circular antenna installation had a diameter of about 200 m (≈660 ft). That would have been more appropriate for a standard ½ wavelength wire dipole, resonant on an operating frequency around 300/(2x200) ≈ 0.715 MHz = 715 kHz. Undoubtedly, small standard commercial quenched spark gap transmitters from Telefunken were used. They had an operating frequency of ca. 500-1000 kHz. However, there is no law of physics that states or implies that an antenna will not radiate efficiently, unless it is dimensioned so as to be resonant at the operating frequency. Shorter dipoles could have been used (with loss of directivity), with appropriate impedance adaptation between the transmitter output and the antenna (which causes loss of power). Then again, the stated qualification "small" is relative, and no reference is provided, such as the electrical wavelength or the physical size of a human. Note that either way, even a diameter of 200 m was small compared to the wavelength of several km (!) of early transmitter systems.

You may wonder "16 does not divide nicely into the 360° of a compass. So, why 16 dipoles and not 18?" Astronomers already divided the circle into 360 degrees in antiquity. However, the magnetic compass came into use only about 1000 years ago. Initially, sailors referred to eight principal wind directions: north, northeast, east, etc. I.e., the four cardinal directions and the four intercardinal (= ordinal) directions. As nautical compasses improved, the compass rose ("scale") was further divided into eight "half winds", to form the 16-wind compass rose. A further split added 16 "quarter winds", for a total of 32 "compass points" (D: "nautische Strich", "Kompassstrich"). Each point of the 32-wind rose represents a compass sector of 360°/32=11¼°.

The Minister of Public Works explicitly stated in a letter of November of 1909, that the Prussian Building Authority went public with their system concept, in order to make it "unpatentable" (ref. 187A1, 187A5). Per § 1 and §2 of the German patent law of 1891 (applicable in 1909): "Patents are only awarded for new inventions that have a commercial application" and "An invention is not considered new, if at the time of filing, the invention has already been published within the last 100 years, or has evidently been used within the country such that an other expert could use it." Therefore, the publication indeed effectively blocked such a patent.

The transmitter antenna system comprised dipole antennas, because 1) they have a clear directional radiation pattern, and 2) their construction is very simple.

NOTE that in some old literature and patents, the term "dipole" is used for each "dipole half" (a.k.a. "leg") and each "half" is considered and counted as a separate antenna. Likewise, the words "transmitter" ("Sender") and "receiver" ("Empfänger") are often used for the transmitting or receiving antenna, not for the device that energizes the antenna with radio-frequency signals or converts radio signals captured by the antenna to audio signals. Also be aware that through the 1940s, there are cases where "Ultra High Frequency" (UHF) is used as the frequency-equivalent of the "ultra short wave" (D: "Ultrakurzwelle", UKW) band. The prefix "ultra" simply means "beyond" in Latin. In modern times, the frequency band above HF (3-30 MHz) is actually the "Very High Frequency" (VHF) band of 30-300 MHz, whereas UHF is 300 MHz - 3 GHz. 

The next figure shows the doughnut (torus) shaped radiation pattern of a dipole antenna:

Dipole pattern

Fig. 47: Radiation pattern of a dipole in "free space"

Dipole pattern

Figure 48: 2D dipole pattern

The cross-section of the doughnut has a "figure-of-8" shape. This is very directional, with a sharp null direction along the two radiating elements. I.e., through the center of the doughnut hole. Note that the "null" minimum is much sharper than the flat maximum. Hence, the "null" is preferred for direction-finding.

However, this 3D pattern is only valid in so-called "free space". That is, very far away from ground, from reflective objects, and from objects that can electrically couple with it. Typically not stated in textbooks, is that doughnut represents "total gain" of the antenna. This is the combination of "vertical gain" (i.e., the relative strength of the radiated vertically polarized field) and "horizontal gain". These gains have quite different patterns! The closer a dipole is to ground (or an equivalent horizontal reflecting ground plane), the more of its radiated energy will be reflected upward. The antenna becomes a "cloud warmer" when used for transmission! With decreasing installation height, the 3D total-gain pattern becomes oblong, shorter and taller. That is: less directive. For low angles (i.e., closer to the ground), the "total gain" radiation pattern becomes peanut shaped - still directive, but not as much as in free-space. The "vertical gain" and "horizontal gain" patterns remain quite directional. See Figure 48 below.

Some older literature (e.g., ref. 187C1-187C3 (Telefunken, 1912), 187E1-E2) only appears to consider "vertical gain", which has its maximum in the extended in-line direction of the dipole wires. However, the "horizontal gain" and "total gain have their (larger) maximum broadside to these wires, and a "null" in-line with the wires. This may explain some mixed test results at that time, with horizontal and vertical antennas on the receiver side...

Dipole pattern

Fig. 49: Radiation pattern of a dipole close(r) to ground

Clearly, the radiation pattern is symmetrical. It has a "null" or minimum direction in two opposite directions. Likewise, it has a maximum in two opposite directions. These bi-directional min and max directions are at right angles (90°, orthogonal). These symmetries pose a problem for direction-finding methods that are based on detection of the min or max direction. There are always two such opposite directions. I.e., there is always a 180° ambiguity! Note that this direction-finding ambiguity problem is exactly the same when using a rotating or rotable symmetrical pattern on the transmitter side, or on the receiver side. Such direction-finding systems provide a Linear Line of Position, as discussed in the radio navigation terminology section. The ambiguity can only be resolved by additional information: triangulation with another station, or being able to exclude one of the two LoP directions by other methods (e.g., one LoP direction is over land, whereas the receiver is at sea).

Due to delays and "adverse cirumstances", the Building Authority performed no further tests during 1909-1910. However, the tests at Müggelsee Lake had been successful enough to warrant construction in 1911 of a new antenna system, this time at the Fog Signal Test Station (“Funknebelsignalversuchsstation”) at Cape Arkona. Arkona (misspelled Arcona in some literature) is located 250 km due north of the center of Berlin, on the tip of the Baltic isle of Rügen - Germany´s largest island. This site was chosen to test under realistic operational conditions, and also such that in case of successful completion of the tests program, the system could be used to secure shipping traffic of the state rail ferry between Sassnitz (Saßnitz) on Rügen, and Trelleborg on the southern tip of Sweden (≈100 km).

Contrary to the installation at Friedrichshagen, this time it was a large antenna system. It comprised 32 short masts (2.6 m, ≈8.5 ft), evely spaced on a circle with a diameter of 115 m (≈377 ft), with a tall mast (2.6+43.8=46.4 m, ≈152 ft) at the center. Sixteen dipoles were strung from the central mast. Ref. 187C1-187C3. The dipoles were arranged radially, in a star configuration, i.e., one for every 11¼ degrees. The center of this star, the feedpoint of the dipoles, was raised more than the tips of the dipoles. Such dipoles are also called "inverted-V" dipoles. The span of the dipoles was about equal to the diameter of the circle. For standard half-wavelength dipoles, this implies a medium-wave operating frequency of about 300/(2x115) = 1.3 MHz = 1300 kHz. Due to the size of the installation, it was decided to involve the Telefunken company. To reduce cost and expedite construction, Telefunken recommended an antenna configuration that was different from the one used at Müggelsee Lake. The Müggelsee configuration turned out to be more suitable. So, the Building Authority decided to continue without Telefunken. Maybe this is why the 1912 Telefunken publications on this topic (ref. 187C1-187C3) mention Friedrichshagen but not Arkona!


Fig. 50: 1911 site plan for the Fog Signal test site at Arkona, with encoding of 16 dipole signals

(source: adapted from de.wikipedia.org, retrieved 15 April 2020)

During the summer of 1912, the Building Authority conducted a second series of tests, this time with an antenna arrangement "similar to that used at Müggelsee Lake, with minor modifications". Construction of this station was completed by October of 1912. It was a small system: eight 20 m tall wooden masts (≈66 ft), evenly spaced around a circle with a diameter of 40 m (≈130 ft), and a transmitter equipment shed near the center. See the photo below. There appears to be a support mast with a ball on top, just to the left of the shed. It is only about half as tall as the other masts, and is not at the center of the circle.


Fig. 51: The eight wooden antenna masts and small equipment shed at the Arkona test site - 1912

(source: 187K)

These antennas were installed within the earthen walls of the 12th century slavic Jarosmargburg hillfort. Remnants of the eight tripod masts and the associated tie down stakes were recorded in an archeologic site survey of 1921:


Fig. 52A: A 1921 archeological survey of the medieval Jarosmarburg site on Cape Arkona

(source: adapted from de.wikipedia.org; original 1921 survey drawn by Robert Koldewey; tripod masts marked blue, stakes marked red)


Fig. 52B: The tip of Cape Arkona in modern times - approximate location of the antenna ring is marked with a yellow circle

(source original unedited photo: unknown)

A much larger antenna circle would not have fit within these earthen walls. The 1921 survey also did not record remnants of a larger circle of masts. So the large antenna system must have been installed somewhere else on the Cape, outside the walls. Note that the entire terrain inside these walls slopes upward towards the cliffs on the eastern side, with a rather steep 6% grade ( ≈3 m rise across the 40 m circle).

Tests were conducted through the end of 1912, using ship-board receivers on a passenger steamer and on one of the rail ferries. These were basically still simple, passive crystal sets ("Detektorempfänger"). Direction finding was possible out to 32 nautical miles (≈60 km), and signals could be distinginguished all the way to Trelleborg (≈100 km). Due to lack of funding, tests could not be repeated under various sorts of bad weather conditions and day/night variations in radio propagation. Possible improvements were considered in 1913 and planned to be implemented and tested at Arkona in 1914, with equipment of the Building Authority, Telefunken, and of the company “Dr. Huth-Berlin”. However, World War I interfered with this plan. War can indeed be quite a nuisance and a kill-joy...

Per ref. 187A7, tests with this small system showed that an accuracy of half a compass point (i.e., ≈6°) was feasible, based on averaging. But doesn't eight masts imply only four dipole antennas?! So, how was this demonstrated directivity obtained? Well, even in Germany, there was no law that dipoles had to be straight! Four dipoles in a star configuration gives you eight dipole halves, evenly spaced by 360°/8=45°. These halves can also be connected as horizontal-V dipoles (bent dipoles), instead of straight dipoles. This way, the "null beam" can be steered in twice as many fixed paired directions, thereby doubling the achievable bearing accuracy without changing the numebr of dipoles. See the figure below (c.f. the 3-dipole example on p. 421 in ref. 186A). The aformentioned Franz Kiebitz actually conceived the required "half angle" antenna switching arrangment:


Fig. 53: Sixteen "null" (or "maximum") directions obtainable with 8 dipoles

(the four possible straight dipoles are marked in green; source antenna switching arrangement: Fig. 1067 in ref. 187R)

Down to a V-angle of 45°, the general shape of the far-field dipole radiation pattern is not very sensitive to that angle. It is also not very sensitive to the sag of the dipole wires towards their feed-point at the center of the circle. But even so, there would still only be 16 paired "null/minimum" (or "maximum") directions spread out over 360°... Note that with 16 dipoles, the same technique would result in 16x2=32 paired "null" directions. Of course, this would have made the antenna switching system significantly more complicated! But that's not all! The system concept requires that the receiver station identify the dipole with the strongest or weakest signal in the direction of the receiver. For this to work, all dipoles must generate the same field strength. This was basically done by ensuring that all dipoles had close to the same antenna current when connected to the transmitter ("it is antenna current that radiates"). For identical dipoles and a homogeneous environment, this is relatively straightforward. This only required a single adjustment of the coupled coils at the output of the transmitter. However, when the dipole configuration is changed from "straight" to "shallow V" or "sharp V", the feed point impedance of the dipole changes significantly. This would then have required switcheable adjustment of the coupling coils, or switching between at least two sets of such coils. This was definitely a disadvantage with respect to simply doubling the number of dipoles. Note that the available literature does not mention how fast any of the above systems rotated. Of course, for proof-of-concept testing and application to navigation of ships, this was not of prime importance.

As mentioned above, the Prussian Building Authority first contacted the Telefunken company in 1906, at which time the company was already investigating directional radio transmissions - without much success. The Authority first engaged Telefunken in 1911 for the activities at Arkona. In 1907, Austrian-born Alexander Meißner (also spelled Meissner) joined Telefunken in Berlin, where he worked on radio direction-finding, radio location, directional radio transmission, and associated antenna technology. Ref. 187G, 187L. Meißner (also) pioneered transmitters using radio tubes/valves, and conceived a vacuum-tube feedback oscillator around the same time (1911-1913) - as did F. Lowenstein, L. de Forest, E. Reisz, C.S. Franklin, H.J. Round, E.H. Armstrong, I. Langmuir, O. Nussbaumer, S. Strauss, A. Sinding-Larsen, and others. Due to near-insuppressible worldwide nationalism (at least regarding inventions), rather lax patent criteria (notably in the USA, to this day), general ignorance regarding "invention" vs. "patent", and limited understanding of foreign languages, typically only one of these names is recognized and credited in any individual country. But anyway...


In 1911, Meißner developed what became known as the "Telefunken Kompass Sender". Ref. 184AE, 187C-187H. This literally translates to "compass transmitting station". Note that this is the opposite of the term "radio compass" in the English and French language, which is a radio direction finding receiving installation. As is clear from his 1912 US patent 1135604, Meißner's system makes several important practical improvements to the rotating dipole-beam system of the Prussian Building Authority:

  • Sequentially transmitting an identical signal (e.g., a short pulse) via the dipoles, instead of a dipole-specific pulse-sequence or tone.
  • Using a timing signal to announce the start of the rotation sequence. This could be a single pulse or a station identifcation code, distinct from the signal transmitted via the dipoles. Of course, this signal now had to be transmitted in a non-directional/omni-directional manner, as it had to be received throughout the entire coverage area of the beacon. A natural choice would be to start the dipole sequence with the dipole that has its null in the north-south direction. The the timing signal would then be equivalent to a North-signal.
  • Patent text page 1 (numbered lines 94-96) proposes to create the required non-directional pattern by simultaneously connecting all dipoles in parallel. From a switching point of view, this not as easy as it sounds. Possibly, this was the configuration tried by Telefunken at Arkona and deemed problematic by the Building Authority... However, the patent also proposes a separate omni-directional "umbrella" antenna (lines 99-101 on text page 1, lines 16, 19, 20 on page 2, and in patent figure 2 shown in Fig. 54 below). Consistent with this, the commutator/distributor in the patent figure connects to the dipoles as well as to an omni-antenna. The latter is accommodated just like an additional dipole would have been, by simply adding two contacts to the commutator.
  • Note that the same transmitter is used for the non-directional transmission as for the directional transmissions. During non-directional transmssion, the radio energy is spread out evenly in all 360° directions, instead of being concentrated in the figure-of-8 beam of single dipole. Hence, the received omni-signal is always weaker than the strongest dipole signal.
  • As shown in patent figure 2, the omni and dipole antennas would share a central mast. The dipole legs are no longer straight: each leg is bent into an inverted-V, and the dipole feed point is near ground level. This is not to be confused with an inverted-V dipole: it has straight legs, and the feed point is higher than the tips of the dipole.
  • The dipoles switching part of the Building Authority system was motorized. A rotary contact arrangement would have been the logical choice. That system also had secondary motorized switching mechanism for creating the dipole-specific "dot" and "dash" pulse sequences. In the patent diagram, this is implemented as an interupter disk in series with the signal from the transmitter. Unfortunately, there are no details available of the Building Authority system that allow us to determine if, or to what extent, Meißner's commutator was different.
  • Significantly simplifying the telegraphist's job at the receiver station. It was no longer needed to interpret the various dot/dash dipole signals. Instead, he simply had to measure the time between the north/time-signal and passage of the weakest dipole signal. The patent proposes a special stopwatch for this purpose. Its needle rotates at the same speed as the antenna commutator.

Interestingly, Meißner's patent was filed in August of 1912, after Telefunken 1912 publications such as ref. 187C1-187C3, and after Telefunken demonstrated a working scale model at the April 1912 Allgemeine Luftfahrzeug-Ausstellung (ALA) aviation exhibition in Berlin, ref. 187M! The patent obviously lists Meissner as inventor. For some reason, it does not list any assignee, even though he was working at Telefunken. There is no equivalent German patent, and elsewhere, there only appears to be one in The Netherlands (octrooi nr. 981, filed July 1912). The same switched multi-dipole star-configuration, but now for radio direction finding receiving purposes, appears in the 1919 German patent 423014 about inductive leader-cable systems for ship navigation.

Telefunken Kompass-Sender

Fig. 54: Cross-section of the antenna system, the transmitter/commutator, and the Telefunken stopwatch

(source: diagram adapted from Meißner's 1912 US patent 1135604; also Fig. 3 in ref. 187C1-C3; stopwatch adapted from Fig. 2 in ref. 187D)

The face of the Telefunken stopwatch shows a circle with 34 tick marks, see Fig. 54. The ticks at the 12 and 6 o'clock position are marked "z" for "Zeit", i.e., reception of the time signal, ref. 186G4. There is one tick mark pair for each dipole antenna. I.e., 32 ticks in total. They are counted from 0 to 31, where "North" = 0 and "South" = 16. The ticks for the cardinal and intercardinal points of the compass are marked with the standard corresponding German letters N, O, S, W, and NO, SO, SW, NW, respectively. Note that the stopwatch does not have a conventional hand (needle), but a double one - across the entire watch face. It represents the two null-directions of a dipole antenna, and the associated 180° ambiguity.

According to ref. 187C1-187C3, the Telefunken Compass transmitted the north/timing signal after each half revolution of the commutator. This makes perfect sense. During a full commutator revolution, each of the 16 dipoles is energized twice, and the receiver station observes two null-passages. If the north/time signal were only sent once, then the second of these null passages would normally be wasted, and double the time between measurements. Note that with a single north-time-signal, using the second null instead of the first, does not change the measured bearing angle, with its 180° ambiguity. The antenna commutator turned at 2 rpm, i.e., one full revolution every 30 sec (though ref. 187F2 states 1 rpm). Hence, half a revolution took 15 sec.

The principle of the Telefunken Compass system is illustrated in the animation below. In this animation, the audio pulse tone is 1000 Hz, the standard for Telefunken quenched spark transmitters, see further below. The tone is not sinusoidal, but a "spark" spike with a decaying tail (see top left-hand corner of Fig. 45 above). This replicates the rough sound of a quenched spark tone. I have included some background static noise, for added realism.

One cycle of the "Telefunken Kompass Sender" system (note: in reality, the time scale & stopwatch needle would move smoothly)

(move mouse/cursor over image to show player controls)

Reports that the system achieved an accuracy of about 3-4° (e.g., ref. 187C1-187C3, 1912), may refer to accuracy of reading the angle on the stopwatch (ref. 2A) or after averaging multiple "null" passages. The average human reaction time to aural stimuli is about 0.25 sec, which would correspond to 6°/sec x 0.25 sec ≈ 1.5°. A significantly improvement the system accuracy would have required an impractical number of dipoles (ref. 184L, 1921).

A prototype of Meißner's Kompaßstation was built and tested at a Telefunken test site in Berlin-Gartenfeld (spelled Gartenfelde in old Telefunken publications). This is an 800 m (≈½ mi) wide triangular area, surrounded by canals. It is located between Berlin-Spandau and what had been the canon and rifle shooting ranges of the Imperial Artillery ("kaiserliche Artillerie") and home of the 1st Prussian Airship Battalion ("1. preußische Luftschiffer-Batalion") at Reinickendorf. The ranges were closed after near-misses with boats on the adjacent lake and a granade hitting a residential house in 1908. The former shooting range and airship area became Berlin-Tegel airport in 1948. Gartenfeld was acquired by the Siemens company late 1910 and was appended to Siemensstadt ("Siemens Town"), adjacent to the south. The Siemens Gartenfeld Cable Works ("Kabelwerk Gartenfeld", part of the Pirelli company since 1998) closed in 2002.

Telefunken Kompass-Sender

Fig. 55: Section of a 1912 map of greater Berlin; the blue triangle marks Gartenfeld island

(source: adapted from wikipedia.org)

Per ref. 187C1-187C3, the central mast of the prototype antenna system was about 20 m tall. This is consistent with the roof ridge of the equipment shed in the photo below being about 2.5 m above ground.


Fig. 56: The Telefunken Compass test site at Gartenfeld near Berlin-Spandau

(source: ref. 187C2)

The figure below shows three photos of Meißner's antenna commutator system. The photo at the center was taken inside the equipment shed in Fig. 56 above. The photo on the right was taken at Telefunken's equipment exhibition at the June 1912 International Radiotelegraph Conference in London (ref. 187D). It was decided at this same conference to relegate transmissions of telegraphy signals used exclusively for direction-finding and location of ships to wavelengths up to 150 m (i.e., frequencies above 2 MHz).

Let's first look at the left-hand photo. It corresponds to Meissner's 1912 US patent 1135604. At the top is a ring with porcelain insulators: one pair for each of the 16 connected dipole antennas and one omni-antenna), each with a ball-shaped contact at the bottom. It appears that these balls could "swing" to and from the central support. The antenna feed-line wires were connected just above the ball contacts. Below this ring are the two rotating arms of the commutator. There is a porcelain insulators at the end of each arm, again with a ball-shaped contact, now pointing upward. Just below the rotating arms are two slip rings that rotate with the arms. Each of the associated sliding contacts is mounted on a vertical rod, with a porcelain insulator at the base. Just above these insulators, the rods are connected to a quenched spark transmitter.

Telefunken Kompass-Sender

Fig. 57: The "Meißner" motorized transmitter distributor / antenna commutator

(source: (left) ref. 187C2 (also in 187C1 & C3); (center) ref. 187C2; (right) ref. 187D)

Also note the vertical disk between the motor and one of these two insulators. The motor is down-geared, and drives the disk and the rotating arms in synchrony. The disk has a series of cams/notches that actuate a normally-closed switch contact. One of the two connections to the transmitter is passed through this contact. This allowed a short Morse-code station identification to be transmitted instead of the start/North pulse signal, while the commutator was connected to an omni-directional antenna. Note that there is no such disk near the commutator-motor in the center and right-hand photos. In the center photo, it appears to be mounted on a small shelf against the outside wall, below a set of eight porcelain insulator disks. This disk has its own motor, so it was not synchronized to the commutator.

In the center and right-hand photo above, the transmitter is mounted directly below the base plate of the commutator. See the next figure. It is a Telefunken model "0,5 T.K." quenched-spark gap transmitter. As the model designator suggests, it had an output power of 0.5 kW. It dissipated over 1 kW. There is a large spiral inductor on the front side of the transmitter. It is made of copper tape. Behind this coil, there are three "Leyden jar" capacitors, connected in parallel. Combined, the inductor and capacitors determine the operating frequency of the transmitter. The frequency was adjustable by selecting taps on the front of the coil. Standard frequency range of the "0,5 TK" was ca. 500-1000 kHz, equivalent to a "medium wave" wavelength of 300-600 m. This could be customized down to 330 kHz (900 m, longwave). Next to the antenna-current meter, there is a frame in which a stack of porcelain insulators and copper electrode disks (with 0.2-0.3 mm mica insulating spacer rings) is compressed. This is a 10-section series spark gap "Funkenlöschstrecke": the actual quenched spark gap device! The copper disks were partially silver plated. They had a large diameter, to increase cooling and thereby improve "quenching" of the sparks. In the center and right-hand photos above, three additional copper-tape coils are visible below the transmitter. They are part of an adjustable antenna tuning circuit.

Telefunken Kompass-Sender

Fig. 58: Telefunken quenched-spark transmitter model "0,5 T.K." used in the early model "Kompass Sender"

(source: (left) ref. 187C; color photos adapted from ref. 186D)

The transmitter was powered by an AC motor-generator. It converted standard 220 V / 50 Hz AC power to 220 V / 500 Hz. A step-up transformer increased the latter to the required high voltage: ca. 8000 volt. The number of spark gaps depended on the desired transmitter power, e.g., 60 gaps for 35 kW. The rpm of the motor-generator was adjustable. This allowed ±30% variation of the nominal tone of the transmitted amplitude-modulated radio signal: 500 Hz AC power generated a 1000 Hz tone, as the transmitter "fires" each half-wave of the AC power (i.e., twice per 500 Hz cycle).

The Telefunken "0,5 TK" sales brochure mentions a range of 100-150 km over land (200 km at night), and 200-300 km over open sea (400 km at night), when using 20-30 m tall T-antennas at both the transmitter and receiver. The 1.5 kW model "1,5 TK" also operated on 500-1000 kHz and had an advertised range of 700 km. Ref. 186D, 186J1.

In 1912, a complete chain of 33 of such beacons was proposed, spaced 50 - 100 km along the entire "political border" of Germany (ref. 187C1-187C3, 187H):

Telefunken Kompass-Sender

Fig. 59: Map of the Telefunken Compass beacon chain along the border of the German Reich, as proposed in 1912

(source: ref. 187H)

The beacon stations were to have used Telefunken ½ kW transmitters, powered by the local electricity grid, and be fully automated: no need for operating staff/personnel.

In 1914, the US Navy began to evaluate radio direction finding systems on Fire Island, a narrow barrier island along the south side of Long Island, New York. The Navy Bureau of Equipment purchased a Bellini-Tosi directional receiver system and a Telefunken Compass transmitter system. Construction drawings of the foundations of the "Telefunken Aerial" and the "Telefunken Compass Building" are dated July 1914 - June 1915 (ref. 187P). Actual testing probably took place in 1916 (ref. 187E1). Per ref. 187N, the central mast was about 30 m tall (100 ft) and the dipole antennas spaced 20°. This spacing implies eight dipoles, so the spacing was actually two compass points, i.e., 2 x 11¼° = 22½°. As shown in Fig. 53 above, it would have been possible to transmit with one compass point spacing. That same reference states that the commutator shorted out all dipoles, except the one being used to transmit. It also states that a different code letter was transmitted via each dipole. I.e., Telefunken had "borrowed" the scheme from the original system of the Prussian Building Authority and Lee de Forest's patent! Demonstrated bearing accuracy was about 5 - 10°, which was deemed acceptable for rough navigation of commercial vessels, but not for war-time military vessels.

In the end, only two "Telefunken Compass" stations were built in Germany. They were constructed early 1917 and were operational through the end of WW-1 (November 1918). One station was built at the village of Bedburg-Hau, on the southeast side of Cleve in Germany, just south of where the river Rhine crosses into The Netherlands. These days, the "Funkturmstraße" (lit. "Radio Tower Street") in Hau is a reminder of exactly where the station was located. Cleve is spelled Kleve since a German spelling reform of July 1935, and is spelled Cleves in English. In 1939, a large "Knickebein" fixed-beam station was built in Materborn, on the west side of Cleve. The second Compass station was built at Tondern, ca. 43 km northwest of Flensburg. This area was Danish territory before 1864 and after World War 1, with the village name spelled Tønder. There was an airship base of the German Imperial Navy ("kaiserliche Marine") on the north side of the village. The two stations were used by German ships, submarines, and for long-range navigation of dirigibles built by the Zeppelin, Parseval, Schütte-Lanz, and Basenach companies (ref. 1, 2, 185G, 185H, 235L). When airship losses became unsustainable (they were an easy prey), they were phased out and replaced by "Groß-Flugzeuge" ("G-Flugzeuge" = "large aircraft" bombers) and "Riesen-Flugzeuge" ("R-Flugzeuge" = "Giant aircraft" longe range bombers, with wings spans of 28-55 m ≈ 90-180 ft). These also used the Compasses. The German military referred to these beacons generically as "Richtungssendeanlage" (RSA), i.e., directionally transmitting station.

Over southwestern England, the Line of Position of the two Compass stations crossed at a sharp angle. Not surprisingly, it was found that this made the position estimates less accurate. This is illustrated in the Figure 43B above.

Obviously, the beacons were deactivated at the end of WW-1. The station at Cleve was dismantled in 1926, on orders of the Belgian occupational forces in that area (ref. 187J). Note: upon German default on WW-I reparation payments, French and Belgian troops invaded the German Rhineland area from January of 1923 until July of 1930. This  basically the German area west of the Rhine river, i.e., all the way up to just north of Cleve, and a strip along the east bank. The industrial Ruhr area was occupied until August of 1925.

According to ref. 187R, the main wooden antenna mast stood 75 m tall (≈245 ft). Per ref. 187J, the trellis mast was made of American pitch pine, a dense high-strength hard wood. Thirty (!) dipoles were suspended from the top of the main mast, down to sixty support masts (standard "Telegraphenstangen", i.e., telegraph/telephone poles) that were spaced evenly on a circle with a diameter of 2x125=250 m (≈820 ft). Note: ref. 187R mentions both 125 and 130 m as diameter. The support masts were 12 m (≈40 ft) tall. There were five evenly spaced "crow's nest" platforms on the main mast, see Fig. 60 below. The dipole wires were strung from each support mast to an insulator on the outside the upper platform, i.e., several meters below the top of the mast. Hence the top of the antennas was ca.70 m above ground level. From there, the wires went all the way straight down and were attached to an insulator at each platform. This implies that there was no separate omni-directional antenna, and that omni-directional transmission was done via all dipoles simultaneously, as confirmed by the schematic in Fig. 61 below.

Telefunken Kompass-Sender

Fig. 60: The wooden central mast of the Telefunken "Kompass Sender" near Cleve (left) and Tondern (center)

(source: ref. 187J (left), Fig. 1090 and Fig. 1085 in ref. 187R)

Compared to older implementations, the number of dipole antennas was increased from 16 to 30. This improved direction-finding accuracy to ca. 2°. Per ref. 187R, there was no Meißner-commutator between the transmitter and the dipoles. Instead, there was a very large toroidal coil ("Trommelspule", "Ringspule") with a diameter of 2 m (6.6 ft)! This coil comprised 720 wire-turns with 60 evenly spaced taps for the 30 dipole antennas. Inside the coil, similar to the Meißner-commutator, an arm rotated. There was a sliding brush at both ends of the arm. It connected via slip rings to a 4 kW Telefunken quenched spark transmitter (possibly a model "4 TV", ref. 186J1). Compared to the standard radio goniometer, this toroidal coil had a more homogeneous coil field, and rotation did not cause undesirable capacitance variation (ref. 184B), and associated frequency variation.

Telefunken Kompass-Sender

Fig. 61: The transmission control system of the Telefunken Kompass stations at Kleve and Tönder

(source: adapted from Fig. 1091 in ref. 187R)

A large number of cam disks was used to transmit the various Morse-code identifier and timing signals, and to switch between the directional and the omni-directional antenna configuration. At the center of the diagram above, there is a cam disk marked "Flimmerzeichen" , i.e., "blinker". Its purpose is to transmit rapid short pulses instead of a constant signal, to improve accurate detection by the receiver station of the signal null/minimum.

The shafts of the cam disks were driven by a system made by the company Carl Zeiss (renowned for its lenses and scientific instruments) in the city of Jena, about 225 km southwest of Berlin. The drive system was regulated by an accurate clock (±0.2 sec/day), made by the Riefler precision-clock company in Munich. For omni-directional transmission, all dipole wires were connected together by bridging the two sliding brushes, while one side of the transmitter was connected to ground/earth.

Per ref. 187R, the Telefunken Kompass stations at Cleve and Tondern used the following transmision sequence, see Fig. 62:

  • First, the station at Cleve ("Station C") repeatedly transmitted its identifier ("Stationszeichen"), the Morse-code letters "CCC", 3x "─ • ─ •", during 42 sec. This was an omni-directional transmission.
  • This was followed by the "start" sequence ("Loszeichen"): the Morse-code punctuation character "=" (dash-dot-dot-dot-dash, "─ • • • ─"), followed by the letters "O" (dash-dash-dash, "─ ─ ─") and "S" (dot-dot-dot, "• • •"). The last "dot" of this sequence was the actual start signal. This sequence was also transmitted omni-directionally.
  • Then a constant tone signal ("Peilungsstrich") was transmitted with rotating directivity for 80 sec, at two rpm. So, receiving stations would observe a signal null/minimum every 15 sec.
  • Finally, a termination signal ("Schlußzeichen") was sent, again omni-directionally: the Morse-code procedure sign (prosign) AR (for the Morse procedure word "new page", dot-dash-dot-dash-dot, "• ─ • ─ •"), followed by the punctuation character ":" (dash-dash-dash-dot-dot-dot , "─ ─ ─ • • •"). The final "dot" coincided with "north" passage of the null-direction, exactly 90 sec after the last "dot" of the "start" sequence.
  • Ten second laters, the station at Tondern ("Station B") would start its 90 sec sequence, but used the Morse-code letters "BBB" (3x "─ • • • ") as station identifier.
  • Both stations transmitted on the same radio frequency, around 165 kHz (1800 m, long-wave).

Telefunken Kompass-Sender

Fig. 62: Relative timing of the Cleve and Tondern Telefunken Kompass stations

(source: Fig. 1088 in ref. 187R)

During 1918, civilian radio listeners in The Netherlands (a neutral country during WW1) became aware of regular transmissions by "mysterious" directional radio stations in Germany, with cyclically varying signal strength. Their observations, conjectures, and conclusions were discussed in several issues of the monthly magazine of The Netherlands' Telegraphy Association, ref. 187Q1-187Q9. These private observations were supplemented with measurements by several direction-finding and listening stations of the Royal Netherlands Navy, Army, and several schools. For example, for the "c" station, the following was observed:

  • Transmission sequences started at 4 minutes past the full and half hour.
  • Each sequence started with omni-directional transmission that consisted of:
  • five groups of three letters "C" (5x3x "─ • ─ •"),
  • then the Morse-code prosign AS (used for both "wait" and for ampersand, i.e., the character "&", "• ─ • • •"),
  • and finally the group "EEE", i.e., three "dots" ("•"). The last "dot" would have signified the "start stopwatch" signal.
  • On other occasions, the "C" station sent its sequences every 15 minutes:
  • the C-series,
  • followed by the "double dash" punctuation character "=" (dash-dot-dot-dot-dash, "─ • • • ─ ")
  • and finally the punctuation character ":". The latter character is "dash-dash-dash-dot-dot-dot" ("─ ─ ─ • • •). Again, the last "dot" signified the "start stopwatch" signal.
  • Some observations only mention gradually increasing and decreasing signal strength, i.e., not stepwise. Others reported that the directional transmission sequence comprised long dashes of about three seconds each (ref. 187Q1).
  • Note that for an antenna system with 16 dipoles, this implies one revolution in 60 seconds, with a 0.75 sec pause between dashes. I.e., as if there was a commutator switches between consecutive dipoles.
  • Some observations mention passage of 5 or 6 minimums during a 90 sec cycle. I.e., 15 sec between minimums. This is consistent with the 2 rpm rotational speed.
  • Based on the received sound, it had to be a "fluitvonkstation", literally a "whistling spark station", i.e., a quenched spark transmitter.

By triangulation, listeners determined that the "C" station was the Telefunken Radio Compass at Cleve, and "B" the station at Tondern. All participating receiving stations were within 100-200 km (≈ 60-125 mi) from beacon "C". Signals received from that beacon never disappeared completely during the minimums. I.e., the minimums of the radiation pattern were not true "nulls". The receivers were 175-500 km (≈ 110-310 mi) from beacon "B". During the long (wide) minimum, no signal was received. Only one listener ever claimed to have heard an "é" ("dot-dot-dash-dot-dot", "• • ─ • •") station.

The 1919 Reichs Patent nr. 328279 of Leo Pungs and Hans Harbich (both of Telefunken's competitor C. Lorenz AG) proposes to replace the toroidal coil with an arrangement of two concentric cylindrical coils, the outer one being a stationary non-contact drum armature ("Trommelspule") with a special coil winding scheme, the inner one rotating and coupled to the transmitter (see Fig. 1083 in ref. 187R). Mr. Pungs (author of ref. 187R) also patented a special stop-clock for use with a Radio Compass (RP 328274, May 1917), to accurately measure the time between two successive null/minimum signal passages, instead of between the North/Start-signal and the first null/minium passage.

Of course, the original Telefunken "Kompass Uhr" stopwatch could still be used, with its nautical "compass points" scale (see Fig. 54). However, a special high-resolution direction-finding stop-clock "Peiluhr" was developed, see Fig. 62 below. Its single-hand made a step every 0.1 sec, making its rotation seem continuous. This, combined with the high number of dipoles (30 vs. 16) and the goniometer instead of a commutator, the obtainable accuracy was improved to about 1° (ref. 187R).

Telefunken Kompass-Sender

Fig. 63: "Peiluhr" direction-finding clock for use with the Telefunken Kompass

(source: Fig. 1089 in ref. 187R)

As Meissner mentions in his 1928 German patent 529891, the accuracy that could be obtained with the Telefunken Compass system depended on the stopwatch operator and the relatively low rotational speed of the beacon. This required averaging of several consecutive bearing measurements, a rather time-consuming process that was only acceptable for slowly moving boats and ships. His patent proposes to replace the stopwatch with an optical indicator that "somehow" rotates synchronously with the beam of a beacon that rotates at very high speed (e.g., 20 rps = 1200 rpm!). The pulses received from sweep-by of the rotating beam would be converted to two almost-stationary light spots (spaced 180°) at the corresponding positions on a compass scale.

This was basically the end of the line for this first generation of rotating-beam radio navigation beacons - until the latter half of the 1920s...


Below is a listing of patents related to radio direction finding, radio location, radio navigation (generally covering the early 1900s through WW2).Patent source: DEPATISnet. Patent office abbreviations: KP = Kaiserliches Patentamt (German Imperial Patent Office), RP = Reichspatentamt (Patent Office of the German Reich), DP = deutsches Patentamt (German Federal Patent Office), US = United States Patent Office, GB = The (British) Patent Office, F = Office National de la Propriété Industrielle (French patent office), AU = Dept. of Patents of the Commonwealth of Australia, NL = Nederlandsch Bureau voor den Industrieelen Eigendom (patent office of The Netherlands).

Note: in the USA and other countries, a company or business cannot apply for a patent. In such cases, the employee-inventor (i.e., the invention was made as part of the employment) has to apply for the patent (or the patent is applied for in the inventor's name), and then transfer (assign) the patent rights and ownership the employer/company. This assignment transfer is typically done during the application process. An inventor who is not obliged to assign the patent to an employer, may assign his patent (transfer of rights, not of invention) to any other party.

Patent number Patent office Applied Inventor / assignor Patent owner / assignee Title (original, non-English) Title (original English or translated) + brief summary
716134 US 1901 John Stone Stone Whicher, Browne, Judkins (trustees) --- "Method of Determining the Direction of Space Telegraph Signals" [Determination of the bearing of a transmitting radio station by means of a rotable loop antenna (or symmetricall arranged pair of verticals) with which "null" signal direction is found.]
716135 US 1901 John Stone Stone Whicher, Browne, Judkins (trustees) --- "Apparatus for Determining the Direction of Space Telegraph Signals" [Identical to Stone's 1901 US patent 716134.]
770668 US 1903 Alessandro Artom Alessandro Artom --- "Wireless Telegraphy of Transmission through Space" [Generation of a "compact cone" [directional beam] of radio waves, by means of combining 2 or more antennas, transmitting with different phases and directions.]
165546 KP 1904 Christian Hülsmeyer Christian Hülsmeyer (Huelsmeyer) "Verfahren, um entfernte metallische Gegenstände mittels elektrischer Wellen einem Beobachter zu melden" "Method for detecting distant metal objects by means of electrical waves" [This is the invention of radar!]
771819 US 1904 Lee de Forest Lee de Forest --- "Wireless Signalling Apparatus" [Improved, simplified devices for localizing direction of a radio station; rotable antenna (horizontal dipole, horizontal monopole + ground/earth, or vertical loop) + detector/coherer + telephone receiver, with or without battery.]
13170 GB 1904 Christian Hülsmeyer Christian Hülsmeyer (Huelsmeyer) --- "Hertzian-wave Projecting and Receiving Apparatus Adapted to Indicate or Give Warning on the Presence of a Metallic Body, such as a Ship or a train, in the Line of Projection of such Waves" [Expansion of his primary German 1904 radar patent 165546, with closely spaced transmitter & receiver antennas that are shielded from each other, antennas with cardanic suspension to maintain their orientation during ship roll & pitch movements, rotable directive transmit antenna (concave / parabolic reflector) with collocated spark gap, fed with high-voltage via slip rings; receive antenna could also made directive in same direction as transmitting antenna by using reflector.]
25608 GB 1904 Christian Hülsmeyer Christian Hülsmeyer (Huelsmeyer) --- "Improvement in Hertzian-wave Projecting and Receiving Apparatus for Locating the Position of Distant metal Objects" [Expansion of his 1904 British radar patent 13170, with constructional improvements to make elevation angle of the transmision antenna variable, so as to be able to find the azimuth & elevation combination with the strongest reflection from the target. This also allows determination of distance ( = range), as elevation angle is determined and antenna mounting height is know. For ship-mounted installation: mounting on fore deck is limited to 180° sweep due to ship superstructure behind it, so a 2nd transmitter / receiver on the aft deck can expand coverage to 360°.]
833034 US 1905 Lee de Forest Lee de Forest --- "Aerophore" ["radiation concentrating device" (directional transmitter such as spark gap + parabolic reflector) that is slowly rotated by a motor that also drives a "signalling wheel" disk (with dots & dash notches + contact) and a voltage generator + up-transformer + oscillator capacitor; the contact interrupts the voltage to generate high voltage pulses for a spark gap. Sends "code signals" (distinct patterns of several dots and/or dashes) in each azimuth sector. Rotating antenna: parabolic reflector + spark gap, or angled mono-pole  as described in the article "Notizen über drahtlose Telegraphie" ["Notes on wireless telegraphy"] by Ferdinand Braun in Physikalische Zeitschrift, Vol. 4, Nr. 13, 1 April 1903, p. 361-364, which includes §2 "Versuche über eine Art gerichteter Telegraphie" ["Tests with a form of directive telegraphy]).
192524 KP 1907 Otto Scheller Otto Scheller "Sender für gerichtete Strahlentelegraphie" "Antenna arrangement for directional radio transmission" [Multi-antenna systems could not be made directional with spark transmitters, as transmitter output could not be split; patent shows how to do this efficiently with undamped-wave transmitter.]
201496 KP 1907 Otto Scheller Otto Scheller "Drahtloser Kursweiser und telegraph" Wireless course indicator and telegraph. [Invention of overlapping beams with equi-signal; English translation is here.]
378186 F 1907 Alessandro Artom Alessandro Artom "Système évitant la rotation des antennes dans un poste de télégraphie sans fil dirigable et permettant en particulier de déterminer la direction d'un poste transmetteur" "System to avoid rotation of the antennas of a directional radio station and in particular enabling determination of the direction of a transmitter station." [identical to Artom's original Italian patent nr. 88766 of 11 April 1907. Invention of the goniometer, often erroneously attributed to Bellini & Tosi, who lost their case in Italian court against Arthom]
943960 US 1907 Ettore Bellini & Alessandro Tosi Ettore Bellini & Alessandro Tosi --- "System of Directed Wireless Telegraphy" [Antenna configuration with 2 perpendicularly crossing triangular loops (with open top = inverted-U with tips nearly touching), using a goniometer. ([FD = Artom's 1907 French patent 378186) to rotate the antenna system's directivity without physically rotating that system. The 2 antennas are excited by a transmitter such that their radiated fields superimpose and combine.]
11544 GB 1909 Henry Joseph Round Marconi's Wireless Telegraph Co. --- "Improvements in Apparatus for Wireless Telegraphy" [For directional receiving purposes: switched directional beams, here obtained with 2 inverted-L antennas.]
1135604 US 1912 Alexander Meissner Alexander Meissner --- "Process and Apparatus for Determining the Positon of Radiotelegraphic receivers" [Invention of stepwise-rotating-beam Radio Compass beacon. (FD: later referred to as the "Telefunken Compass"; also see equivalent Telefunken's 1912 Dutch patent 981).]
1162830 US 1912 Georg von Arco & Alexander Meissner Telefunken GmbH --- "System for signalling wireless telegraphy under the quenched-spark method" [Improved transmission scheme, with loose coupling between tuned antenna and spark generating circuitry, such that the continous sequence of generated spark oscillations is in sync with the oscillations in the antenna, such that they do not (partially) extinguish one another and a nearly undamped wave results.]
1051744 US 1914 Alexander Meissner Telefunken GmbH --- "Spark gap for impulse excitation" [Pair of round spark-gap plates, one with multiple round dimples (or concentric grooves), the other with mating bumps (or concentric ridges).]
981 NL 1912 - Telefunken GmbH "Inrichting voor het bepalen van de plaats van ontvangers (schepen) door middel van draadloze telegrafie" "Arrangement for position determination of receivers (ships) by means of wireless telegraphy" [Equivalent of Meissner's 1912 German patent 1135604.]
299753 RP 1916 Otto Scheller C. Lorenz A.G. "Drahtloser Kursweiser und Telegraph" "Wireless direction pointer and telegraph" [Expanding his 1907 patent with a radio goniometer to couple transmitter to antenna pair; English translation of the patent claims is here.]
328274 RP 1917 Leo Pungs Leo Pungs "Verfahren zur Feststellung der Richtung eines Empfangortes zu einer Sendestation, von der gerichtete Zeichen ausgehen" "Process for determining the direction of a receiving station relative to a transmitting station that is sending directional signals" [Accuracy of bearing determination with stopwatch of rotating-null beacons that transmit north/south signal (such as Meissner/Telefunken Kompass) depends on synchonicity between beacon & stopwatch. Invention proposes stopwatch with compass degree-scale, two hands/needles, both started simultaneously, one stopped upon reception of first null/minimum, the other upon receipt of second null. In ideal case, angle between the 2 pointers is always 180°. A second, rotable scale is aligned with first pointer and value at second pointer shows bearing correction factor if angle when angle is not 180°.]
130490 GB 1918 Frank Adcock Reginald Eaton Ellis --- "Improvement in Means for Determining the Direction of a Distant Source of Elector-Magnetic Radiation" [Receive only; 2 pairs of vertical dipoles, dipoles of each pair connected with a feedline taht includes 180° twist, in order to suppress received horizontally polarized signals. (FD: this patent is sometimes erroneously attributed to R.E. Ellis, who is actually only the assignee who acted as intermediary / patent agent in the patent application, as the inventor / assignor was serving military duty in WW1 France at that time).]
1301473 US 1919 Guglielmo Marconi, Charles Samuel Franklin Marconi's Wireless Telegraph Co. Ltd. --- "Improvements in reflectors for use in wireless telegraphy and telephony" [For receiving & transmission antenna systems; several reflector configurations, comprising screens of parallel rods, strips, or wires. arranged on a parabolic surface; FD: same as marconi/Franklin's 1919 Australian patent nr. 10922.]
328279 RP 1919 Hans Harbich & Leo Pungs Hans Harbich & Leo Pungs "Schaltung für die Richtungstelegraphie mit Vielfachantennen" "Circuit for directional telegraphy with multi-element antennas" [Antenna ranngement (many crossing dipoles connected to taps on a cylindrical coil winding, with a coaxial rotable second cylindrical coil) usable for transmission and reception; instead of rotating contactor/distributor (subject to contact wear & generating noise during reception) or goniometer (small imbalances cause large large phase shift / detuning, hence requiring very loose coupling), instead proposes tightly coupled transformer coupling with single-point-of-tuning for complete transmitter/antenna system.]
198522 GB 1922 James Robinson & Horace Leslie Crowther & Walter Howley Derriman James Robinson & Horace Leslie Crowther & Walter Howley Derriman --- "Improvements in or relating to Wireless Apparatus" [one or more symmetrical pairs of vertical antennas and feedlines, suppression of transmissioin of horizontally polarized signals of each antenna pair by crossing-over of the feedline at the mid-point between paired antenna. (FD: this is the transmission equivalent of the Adcock's 1918 GB patent 130490]
1653859 US 1923 Ludwig Kühn Dr. Erich Huth G.m.b.H. --- "Apparatus for influencing alternating currents" [Method for AM modulating a continuous RF carrier signal with of iron-core choking coils (several configurations), whose self-inductance is varied with the tone or speech audio signal current.]
252263 GB 1924 Alexander Watson Watt Alexander Watson Watt --- "Improvements in and relating to Radio-telegraphy Direction Finding and other purposes" [Adds CRT display to Adcock's DF antenna system arrangement of GB patent 130490]
475293 RP 1926 Hidetsugu Yagi Hidetsugu Yagi "Einrichtung zum Richtsenden oder Richtempfangen" "Arrangement for directional transmission or reception" [Invention of the "Yagi" / "Yagi-Uda" beam antenna; vertical monopole + ≥1 reflector (≥λ) + ≥1 director (≤½λ), spaced ¼λ); German version of the original 1925 Japanese patent nr. 69115; also see ref. 229H]
1860123 US 1926 Hidetsugu Yagi Radio Corp. of America (RCA) --- "Variable directional electric wave generating device" [Placing a vertical (passive) conductor or antenna at some distance of a likewise vertical main (but energized) antenna, and that passive conductor is resonant at a frequency lower than that main attenna (i.e., is at least ½λ long), then the conductor will reflect the waves of that antenna (project them away), and shape the radiation pattern of that antenna in a directive manner accordingly. Conversely, a conductor with a higher resonant frequency than the main antenna (i.e., is shorter than ½λ) will direct the waves of that antenna in the directions of that conductor. Patent refers to it as a beam antenna. Illustrated with several circular configurations of multiple conductors; also see ref. 229H]
481703 RP 1927 Dr. Max Dieckmann, Dipl.-Ing. Rudolf Hell Dr. Max Dieckmann, Dipl.-Ing. Rudolf Hell Funkentelegraphische Peileinrichtung Direction-finding system for spark transmitter stations [RDF system with stationary loop and a reference antenna, fast switching between antennas, galvanometer "on course" instrument]. Follow-up patent 482281, also 1927, uses pair of switching valves instead of motorized inductive coupler.
1741282 US 1927 Henri Busignies Henri Busignies --- "Radio Direction Finder, Hertian Compass, and the Like" [D/F receive; 2 perpendicularly crossing loops (each with a signal amplifier) + 2-coil galvanometer needle instrument that points at compass scale with 0/90/180/270° ambiguity; ambiguity resolved by slightly rotating the loop's pattern with a servo-driven capacitive goniometer; third config, also to eliminate ambiguity, with separate vertical omni antenna, to yield rotable cardioid pattern).]
632304 F 1927 Alexandre Koulikoff & Constantin Chilkowsky Alexandre Koulikoff & Constantin Chilkowsky "Procédé et dispositifs pour le mesure des distances au moyen d'ondes electro-magnétiques" "Method and apparatus for the measurement of distances by the use of electromagnetic waves" [invention of the radio responder / transponder and distance / range measurement obtained therewith; two receiver / transmitter stations, one initates transmission of a (pulse?) signal. Upon receipt, the second station automatically also transmits a (pulse?) signal (at the same or different frequency). Upon receipt by the first station, the latter automatically again transmits a signal, etc. The resulting back & forth transmissions have a modulation with a beat frequency that is proportional to the distance between the stations. Conversely, in absence of significant time delay between reception and tranmissions, the distance is equal to the speed of light divided by twice the beat-frequency; identical to the1928 GB patent nr. 288233 of the same inventors]
305250 GB 1927 Alexander Watson Watt & Labouchere Hillyer Bainbridge-Bell Alexander Watson Watt & Labouchere Hillyer Bainbridge-Bell --- "Improvements in and relating to Apparatus adapted for use in Radio-telegraphic Direction Finding and for similar purposes" [Expansion of their 1924 GB patent 252263; adds omnidirectional / non-directional sense antenna.]
1937876 US 1928 Eugene S. Donovan Ford Motor Company --- "Radio beacon" [A/N beacon, 2 orthogonal crossing triangular loop antennas (one "A", the other "N"; top/tip grounded, goniometer for rotating combined pattern, remote control, separate low-power transmitter + vertical omni-directional cage antenna for alternating "station indicator" (omni overfly-marker beacon; also to be installed separately along airway) or telegraphy message broadcast; equisignal beam width of 6 miles at 200 miles range (i.e., 1.2°) based on experiments; no specific modulation tone implied]
1831011 US 1928 Frederick A. Kolster Federal Telegraph Co. (part of ITT in 1928) --- "Radio beacon system" [upward beam with hollow conical radiation pattern, in-ground antenna + parabolic reflector; related US patents: 1820004 (1928, Geoffrey G. Kreusi "Aerial navigation system and method"), 1872975 (1928, Frederick A. Kolster "Navigation system and method"), 1944563 (1931, Geoffrey G. Kreusi "Directional radio beam system")]
529891 RP 1928 Alexander Meissner Telefunken GmbH "Verfahren zur drahtlosen Richtungsbestimmung" "Method for wireless determination of direction" [Improvement of Compass with stopwatch, results depend on stopwatch operator and relatively low speed of beacon rotation, hence, requires time-consuming repeated measurements and averageing. Patent: automatic, replace stopwatch with an optical indicator that (somehow...) rotates synchronously with beacon, light pulses light up at 2 spots on compass scale, based on reception of pulses from beacon beam rotating at 10-20 rps (!!!)]
502562 RP 1929 Ernst Kramar & Felix Gerth C.Lorenz A.G. "Verfahren zum Tasten von Richtsendern für rotierende Richtstrahlen" "Method for keying directional transmitters for rotating directional beams" [Using two iron-core choking coils (per Kühn's 1923 German patent 165385, but switching between 0 & 100% saturation, instead of analog modulation) for alternatingly connecting two antennas to a transmitter without using contact-switches or relays]
1941585 US 1930 Eugene Sibley Eugene Sibley --- "Radio beacon system" [A/N beacon with two orthogonally-crosssing rectangular loop antennas, separate synchronized "A" and "N" transmitters. However, not interlcoking A & N Morse characters (and "T" equisignal), but 5-bit Baudot-type encoding of A & N (11000 and 00110 respectively) and K (11110) equisignal. Combined with a "Teletype" keyboard teleprinter system for transmitting the (adjustable) beacon course to the pilot via the beacon's directional loop antennas, or course, weather and other broadcast info, via the non-directional marker of the beacon station or en-route marker beacons. Automatic compact "Teletype" tape printing telegraph in the cockpit. Demonstrated.]
546000 RP 1930 Meint Harms Meint Harms "Verfahren einer selbsttätigen Ortsbestimmung beweglicher Empfänger" "Method for position finding by a mobile receiver" [Invention of hyperbolic radio navigation; autonomous localization of a moving receiver by using 2 (or more) coherent CW transmitter stations with spacing equal to integer multiple of the wavelength. One station acts as master, with stable phase, the second is synchronized to it and transmits on 2x the Master frequency (or, in general, any frequency that is coherent with the Master's) without phase shift. Receiver has 2 antennas, one for the Master frequency, the other for the Slave frequency. The receiver amplifies both signals separately, while at the same time doubling (or whatever the coherent Amster-Slave frequency factor is) the frequency of the Master's CW signal. The 2 resulting same-frequency CW signals are combined/compared, and the result drives an electro-mechanical up/down counter. Starting at a know position, each time movement causes Master-Slave phase difference to make a 360° → 0° transition, the counter value is changed in one direction, and in the opposite direction upon each 0° → -360° transition. So, during movent along a 0° phase difference hyperbel, the counter vale is not changed (FD: i.e., counter value change corresponds to 1λ hyperbel change).]
363617 GB 1930 Reginald Leslie Smith-Rose & Horace August Thomas Reginald Leslie Smith-Rose & Horace August Thomas --- "Improvements in or relating to Wireless Beacon Transmitters"  [Rotating beacon, 6-10 ft square loop antenna, rotating about a vertical axis at 1 rpm; transmitting a characteristic signal when passing the geographical meridan [ = north/south direction], receiver uses stopwatch to measure time between passage of reference signal and signal's minimum-intensity passage; vertical loop or inclined loop with suppression of non-horizontal radiation; also covers version comprising 2 pairs of vertical antennas with a goniometer with 1 stator and 2 rotors.]
661431 RP 1930 Ernst Kramar C. Lorenz A.G. "Einrichtung zur Richtungsbestimmung drahtloser Sender" "Arrangement for direction finding of wireless transmitters" [Apparent width/sharpness of "A/N" (or similarly complementary keyed) equisignal beam, depends on accuracy of the A/N signal-strength comparing electronic instrumentation that is used for determining course deviation, esp. for visual indicator. Constant two-tone instead of A/N keying system requires accurate tone filtereing and high signal strength and/or high-gain reed-instrumentation. Significant improvement of sensitivity / apparent beam-sharpness by using (diode tube) rectifiers with quadratic characteristic, to increase the apparent relative signal strength of the received 2-tones.]
2014732 US 1930 Clarence W. Hansell Radio Corporation of America (RCA) --- "Radio beacon system" [3 crossing rectangular loop antennas (or 3 vertical antennas on corners of triangular footprint) + 1 vertical omni-directional antenna at center; cardiod pattern; transmitter = crystal controlled carrier-frequency generator + modulator + "modulating wheel" tone generator driven by synchronous motor (continuously variable pitch = FM modulation with tone "chirp": 2 Hz sawtooth signal with 150-250 Hz linear tone ramp) + 4 amplifiers (1 for each of 3 loops/verticals, 1 for central vertical omni antenna). Synchronous 2 rpm motor also drives goniometer to continuously rotate the cardiod pattern. Receiver audio output is fed to a circular indicator with 36 reeds, each tuned to a tone in the 150-250 Hz range. Patent claims system was actually demonstrated.]
349977 GB 1930 John M. Furnival, William F. Bubb Marconi's Wireless Telegraph Co. Ltd. --- "Radio beacon" [2 orthogonal crossing triangular loop antennas + goniometer; cam-driven callsign/identifier Morse code; standard 2 or more adjustable equisignal directional zones (e.g., cam-driven A/N system), and rotating directional signal/beam (cardioid or figure-of-8 using same 2 loop antennas) with predetermined speed + omni-directional reference direction marker (e.g., north passage ID), i.e., the 1912 Telefunken/Meißner system per German patent 1135604]; same as the Furnival/Bubb US patent 2045904 filed a year later (in 1931), which has, however, Radio Corporation of America (RCA, originally Marconi's Wireless Telegraph Co. of America, "American Marconi") as assignee/owner.
1945952 US 1930 Alexander McLean Nicolson Communications Patents, Inc. --- "Radio Range Finder" [One of the stations initiates an RF carrier impulse of predetermined duration (e.g., 10-100 cycles of a 1 MHz carrier). The receiver of the second station (referred to as "reflecting" station) keys the associated transmitter for the duration of the received pulse. The resulting is received back at the initiating station, after round-trip travel time at the speed of light. That time is proportional to twice the distance between the stations. Like the second station, the receiver in the initiating station now keys the associated transmitter for the duration of the received pulse. This results in continuous back-and-forth transmissions. The resulting beat-frequency indicated on a meter instrument with distance scale. (FD: this method is a copy of the one in the 1927 Koulikoff & Chilkowsky responder/transponder patents FR632304 and GB288233!) In a second embodiment of the method, a manually variable re-transmission delay is used in the originating station is used, which is adjusted until the circulating beat frequency is zero. Patent claims that meter or audible tone may also indicate direction of travel. However, it can only do so in the sense of increasing or decreasing distance (i..e, not bearing)! ]
1949256 US 1931 Ernst Kramar C. Lorenz A.G. --- "Radio Direction Finder" [Visual course-deviation indicator/meter with dial/scale, for use with an equi-signal beam fixed course-beacon (e.g., A/N, or easier to interpret by pilot: E/T = dot/dash). Four embodiments (circuit diagrams) shown, all transformer-coupled audio output of receiver, a rectifier (tube/valve) with quadratic characteristic (to obtain high gain for small differences), and a galvanometer. The meter-needle swings about the non-zero deflection corresponding to the equi-signal, in the rhythm of the received dots & dashes, and the swing amount depends on the relative strength ( = course deviation direction and amount). Note: this is not a "kicking meter" arrangement, in which dot/dash pulses are passed through an inductive differentiating circuit, and meter deflection is about the zero indication. Also proposes transmitter keying not with square pulses, but rounded pulses with "rapid rise"/"slow decay" pulse flanks for one of the two overlapping beams, and the opposite for the complementary beam.]
1923934 US 1931 Frank G. Kear US Government --- "Radio beacon course shifting method" [shift 2 beacon courses from their normal 180° displacement to align them with 2 airways that intersect at an angle other than 180°; expand 2-loop/2-pair antenna config with separate vertical antenna (inductively coupled to one of the goniometer primaries) whose omni-directional patternn combines with the figure-8 of 1 loop to create a cardioid.]
1992197 US 1932 Harry Diamond US Government --- "Method and apparatus for a multiple course radiobeacon" [rapid increase in number of airways emanating from major airports means need beacon capable of marking > 4 courses; 3-tone beacon with up to 12 simultaneous courses; 2 triangular vertical loops crossing at 90°, several transmitter configurations (transmitter with master oscillator (carrier freq) + 3 intermediate modulator-amplifiers (65, 86⅔, 108⅓ Hz tones) + 3 final amplifiers, special goniometer with 3 stators (1 for each PA, spaced 120°) + 1 rotor (2 coils crosssing at 90°, each coil 3 sections); several other transmitter configurations.]
1913918 US 1932 Harry Diamond & Frank G. Kear US Government --- "Triple modulation directive radio beacon system" [expansion of H. Diamond triple-modulation/12-course beacon system 1932 US patent 1992197, same diagrams, adding method for shifting the normally 30°-spaced individual courses of the 12-course beacon, to align them to the airways.]
577350 RP 1932 Ernst Kramar C. Lorenz A.G. "Sendeanordnung zur Erzielung von Kurslinien" "Transmission arrangement for creation of course lines" [This is the invention of what was later called the "Lorenz Beam", localizer part of the Instrument Landing system; create equisignal beam, not with two separate directional antenna systems with overlapping patterns, but with a single omnidirectional vertical dipole antenna whose continuously active circular pattern is alternatingly deformed into a bean-shaped pattern to the left and right, by activating a corresponding parallel vertical reflector ( = passive) that is placed at some distance to the right & left of the vertical antenna. The two reflectors are alternatingly enabled in the standard A/N or similiar dots/dashes rhythm. The shape of the "bean" patterns depends on the length of the reflector rods and the distance between the reflectors and the dipole antenna. This method also eliminates key-clicks, since the vertical dipole is allways energized (i.e., not keyed).]
592185 RP 1932 Ernst Kramar & Felix Gerth C. Lorenz A.G. "Gleitwegbake zür Führung von Flugzeugen bei der Landung" "Glide path beacon for guiding airplanes to landing" [Blind/fog landing requires localizer/course beam and glide-path guidance. The latter follows the curved constant-field-strength path upon beam intercept. So far, ground stations used a LW localizer beam and separate VHF glide path beacon. This requires two complete beacon transmitter and receiver systems. Patent proposes simplification by using a single VHF equisignal beam beacon system with complementary keying (with choking-coils; FD: see Kühn's 1923 US patent 1653859 and Karmar/Gerth's 1929 German patent 502562) with asymmetrical pulses (short-rise/long-fall times for one beam and the opposite for the other beam; here: triangular pulses (FD: Kramar's patent 1949256 proposes rounded pulses). The VHF receiver's audio output is rectified. The rectifier output is fed to a galvanometer that indicates the combined/summed strength of the two beams, and is used to fly a constant-strength curved glid path. The rectifier output is also transformer-coupled to a push-pull amplifier stage that drives a kicking-meter (alternatively, the rectifier output can feed a differential-galvanometer). This meter indicates course deviation.]
405727 BP 1932 --- C. Lorenz A.G. --- "Directional radio transmitting arrangements particularly for use with ultra-short waves " [Same as Lorenz' 1932 German patent 577350]
589149 RP 1932 --- C. Lorenz A.G. "Leitverfahren für Flugzeuge mittels kurzen Wellen, insbesondere ultrakurzer Wellen" "Method for guiding aircraft by means of short waves, in particular ultra-short waves" [Landing beacon arrangements to accommodate final descent to a landing from various heights, in particular steep descents from higher altitudes, and glide path intercept (FD: from below = the way it shoud be done) from greater distance. One arrangement with standard Lorenz course beacon ( = vertical dipole + 2x reflector) placed at the approach end (!!!!) of the runway (serving as course beacon and runway marker beacon), and a standard equisignal glide path beacon placed at the departure end (!!!) of the runway. By using different modulation tones, both could operate on the same frequency (in particular with appropriate tone filters at the receiver). Other arrangement with two co-located standard Lorenz course beacons side-by-side, the plane of the antenna systems of these beacons at an appropriate elevation angle instead of vertically (to generate glide path beam of 8-11° (FD: vs. 3° standard in modern times), and at an angle with respect to each other such that their equisignal beams cross; slightly expanded by Lorenz' same-title 1933 German patent 607237.]
1961206 US 1932 Harry Diamond US Government --- "Twelve-course, aural type, triple modulation directive beacon" [Explicitly aural beacon ( = requires interpretation of 3 audio tones (e.g., 850, 1150, 1450 Hz) by pilot, i.e., not 12-course VISUAL beacon with visual instrument to interpret the tones; Aural 12-course beacon were considered impossible, as for 6 of the 12 courses, the 2 overlapping tones that form the equi-beam are overpowered a much stronger figure-8 lobe of the 3rd tone; LW (e.g., 290 kHz) transmitter blockdiagram for 2 configs; keying device between modulators with slip contacts on rotating cylinders with patterns of conductive patches)pilot selectable audio filters.]
2093885 US 1932 Ernst Kramar & Felix Gerth Standard Elektrik Lorenz A.G. --- "Means for guiding aeroplanes by radio signals"  [Two overlapping VHF beams for lateral guidance, curved glidepath on constant signal strength of same 2 beams; FD: equivalent to Lorenz' 1932 German patent 592185.]
408321 BP 1932 --- C. Lorenz A.G. --- "Radio beacon for directing aircraft" [Two overlapping VHF beams for lateral guidance, curved glidepath on constant signal strength of same 2 beams; FD: equivalent to Lorenz' 1932 German patent 592185.]
2028510 US 1932 Ernst Kramar C. Lorenz A.G. --- "Transmitter for electromagnetic waves" [FD: equivalent to the 1932 German "Lorenz Beam" patent 577350.]
1981884 US 1933 Albert H. Taylor, Leo C. Young, Lawrence A. Hyland Albert H. Taylor, Leo C. Young, Lawrence A. Hyland --- "System for detecting objects by radio" [Detection of moving objects (e.g., aircraft, ship, motive vehicle), system comprising CW transmitter and remotely located receiver, continuously receiving ground waves directly from transmitter (constant signal), and intermittently receiving skywaves that are not reflected (!!!) but re-radiated by such conductive/metallic objects (or parts thereof) that have a size of ca. ½λ of the transmitted CW signal, and that interfere/combine with the ground waves signals (causing variable amplitude at receiver). Amplitude of the interence pattern signal fluctuates when object moves, more rapidly (and with larger amplitude) when moving over receiver or transmitter site. Also, moving parts of the object (e.g., rotating propeller(s) = "propeller effect"), cause superimposed distinguishable modulation of the interence pattern signal. Ground wave may be extinguished by the time it reaches receiver, or be transmitted in dirction of receiver if using directional transmitter.]
2121024 US 1933 Harry Diamond US Government --- "Radio transmitting and receiving system" [System for simultaneous transmission of radiotelephone (e.g., broadcast of weather & landing conditions) and radio range beacon signals. For some time, these 2 radio services used different radio frequencies; due to expansion of beacon network, frqeuencies becoming scarce. Method for simultaneous transmission, without overlapping modulations. 2 loop antennas for beacon service, separate omni antenna for broadcast service; single master RF oscillator for both services, with 3+1 intermediate modulator amplifiers (3 keyed tones + microphone or recorded message), and 3+1 final amplifiers; 2-outputs tone filter unit between receiver and headphones, with LPF for beacon signals and HPF for broadcast audio.]
2172365 US 1933 Harry Diamond US Government --- "Directive antenna system" [Radio range beacon; to eliminate erroneous course indications with crossing loop beacons due to "night effect", now antenna configuration with 2 pairs of 2 vertical antennas, evenly spaced, each with ground plane, all with same feedline distance to transmitter, coupled to a single transmitter via a radio goniometer and tuned feedlines to a coupling transformer for each antenna pair, with 180° twisted feedline between on the antenna side of these transformers. Refers to patents GB130490 (1919), GB198522 (1923), and GB363617 (1932).]
1999047 US 1933 Walter Max Hahnemann C. Lorenz A.G. --- "System for landing aircraft" [Upon intercept, as indicated on meter, the pilot adjusts vertical flight path as necessary, such that the meter deflection does not change from the indication at moment of intercept (absolute deflection is not important). Various converging curves can be selected ( = steepness), by adjusting the receiver/indicator gain, also possible a receiver device that is triggered by reception of the marker beacon and with a timer, moves the indicator scale to indicate estimated height above ground.]
2348730 US 1933 Francis W. Dunmore & Frank G. Kear US Government --- "Visual type radio beacon" [Fixed course beacon comprising 2 pairs of "transmission line" (TL) antennas (pair of vertical monopoles with ground planes, instead of 2 crossing loops) with figure-8 pattern (90° phase shifted excitation), with a different modulation tone (65 & 83⅔ Hz) for each pair (feed-line arrangement to eliminate "night effect"), combined with two co-located omni-directional transmissions on same frequency but with 270° phase difference, with the same 2 modulation tones; combined "figure-8 and omni" pattern pairs form cardioid pattern; two 2 overlapping cardioids form 2 equisignal course lines; refers to description in CAA-ACM 1932 No. 2.]
653519 RP 1933 --- Marconi's Wireless Telegraphy Co. Ltd. "Verfahren zur Übermittlung von Nachrichten allert Art auf drahtlosem Wege" "Method for wireless transmission of messages" [directly readable, omni-directional transmission of, e.g., weather data, as pointer on CRT display with scale, without synchronization complexity of TV or fax]
2072267 US 1933 Ernst Kramar C. Lorenz A.G. --- "System for Landing Aircraft" [Expanded by 1937 follow-up Lorenz' 1937 US patent 2215786 "System for landing airplanes".]
2120241 US 1933 Harry Diamond & Francis W. Dunmore US Government --- "Radio guidance of aircraft" [UHF landing/take-off beam beacon, method and apparatus, able to serve all wind directions with a single beacon that has variable glide path steepness to a proper/predefine touch-down point. Demonstrated at College Park/MD and Oakland/CA airports. Beacon antenna placed in a pit, just below ground level of the airfield / landing zone. First antenna arrangement: horizontal UHF dipole. With this installation position, the dipole's torus radiation pattern in free space (FD: i.e., figure-8-on-its-side vertical cross-section in all directions) is pushed upward with increasing distance from the antenna, enabling curved constant-field-strength glide path. The horizontal dipole can be made rotable about its vertical axis (with remote controlled motor and 2 slip rings to feed the antenna) to accomodate any pair of 180° spaced directions (2-course). A rotable 4-course equivalent can be obtained by using two crossing dipoles with 2 pairs of slip rings.]
2044852 US 1933 Ernst Kramar C. Lorenz A.G. --- "Electric indicator for comparing field intensities" [E/T equisignal beam deviation indicator; standard circuitry with rectifier and transformer; galvanometer. References 1928 US patent 1782588 "Electrical mesasuring instrument" (2-pole galvanometer with rotary coil) by F.E. Terman. The desrired meter sensitivity reduction for increasing meter / needle deflection is obtained electromechanically instead of electronically, by tapered (instead of concave) shape of the galvanometer poles.]
616026 RP 1934 --- C. Lorenz A.G. "Sendeanordnung zur Erzielung von Kurslinien gemäß Patent 577 350" "Transmission arrangement for obtaining course-lines per Lorenz' 1932 German "Lorenz beam" patent 577350" [vertical dipole + two near-resonant reflectors]
612825 RP 1934 --- C. Lorenz A.G. "Verfahren zum Betrieb von Funkbaken" "Method for operating a radio beacon" [2-course A/N or E/T beam; left/right beams are swapped, based on which of the two courses is actively used by aircraft, such that indicated left/right course deviation indications is correct for both, i.e., A & N (E & T) always on the same side of the equisignal beam when approaching the beacon]
2196674 US 1934 Ernst Kramar & Walter Max Hahnemann C. Lorenz A.G. --- "Method for Landing Aircraft" [Localizer beacons that are used to provide guidance for curved, constant field-strength approach to landing, typ. depend on constant transmitter power and constant receiver gain (FD: at least during the beam intercept and final approach & landing phase). The latter is more difficult to ensure than the prior. Method usable with equisignal course beam beacons, elevated/upwardly transmitted radiation patterns, and torus-shaped patterns (FD: e.g., from a vertical dipole or monopole). Method uses a marker beacon (accoustic or - preferred - radio) below the intended point of positive intercept of the desired constant field-strength curves. This also supports using the same curve, even if intercepting at a different altitude. Aircraft to approach & intercept the beam (FD: from below) at a predermined altitude. The marker beacon may transmit vertically or at some other, steep elevation angle in te direction of the approach. Upon intercept, as indicated on meter, the pilot changes vertical flight path such that the meter deflection does not change from the indication at moment of intercept (absolute deflection is not important). Various converging curves can be selected ( = steepness) with method covered by Hahnemann/Lorenz' 1933 US patent 1999047. Patent also references Kramar/Lorenz' 1932 US "Lorenz Beam" patent 2028510]
2217404 US 1934 Walter Max Hahnemann & Ernst Kramar C. Lorenz A.G. --- "System and Method for Landing Airplanes" [Expansion of Hahnemann/Kramar 1934 US patent 2196674 with the manually adjusted receiver/indicator configurations per Fig. 4 & 5 of Hahnemann's 1933 US patent 1999074]
2025212 US 1934 Ernst Kramar C. Lorenz A.G. --- "Radio Transmitting Arrangement for Determining Bearings" ["Lorenz Beam" beacon station with continously rotating equisignal beam course direction. Standard antenna arrangement (continously excited vertical dipole (with omni pattern), a vertical reflector on each side, motorized A/N keying for complementary reflector interruption). However, now with the reflectors continously rotating about the vertical dipole, with the relays used to interrupt each reflector controlled via slip rings, to create a rotating 2-course equisignal beam system. This is much simpler than an arrangement with a motorized radio goniometer. During passage of the equisignal beam pair through a predetermined bearing (e.g., north/south), the interruption of the reflectors is briefly stopped and a predetermined combination of Morse characters is omni-dirctionally transmitted via the vertical dipole (keying by hand or motorized). receiver station determines bearing to/from station based on timing beam passage after "north" signal (FD: = Telefunken Compass stopwatch method). Alternatively, a short special character (e.g., a single dot) could be tranmsitted omnidirectionally at regular bearing increments (e.g., every 5°), and the receiver's bearing be estimated simply by counting the number of received dots since the north/south signal reception]
2083242 US 1935 Wilhelm Runge Wilhelm Runge --- "Method of Direction Finding" [3D RDF method, searching direction with maximum signal strength (unlike minimum method, accuracy is not affected by background noise, static, etc.) with a highly directional antenna system; antenna beam is moved, such that its narrow/sharp beam is precessed (conical movement) about a pointing direction (without changing the polarization direction of the antenna). Beam precession is obtained either mechanically (precession manually or with motor drive, and receiving dipole with a parabolic reflector, on a platform with manual or motorized rotation about vertical axis to change bearing, manual elevation axis adjustment; adjustments until strength of received signal remains constant (FD: this is referred to as "hill climbing" technique in modern control systems engineering terminology), or electrically (a stationary "flat" symmetrical 2D array of dipoles, with beam sweeping by means of changing phases (feed line lengths) between the dipoles.]
2184843 US 1935 Ernst Kramar C. Lorenz A.G. --- "Method and Means for determining Position by Radio Beacons" [Method of determining bearing at the receiving station, automation of this method, for use with rotating equisignal beam beacon with 1) E/T keying (60 per 360° rev of the beacon = 15 per quadrant = 1 per 6° rotation), 2) omni-directional transmission of sync/timing/zero signal upon beam passage through specific direction (e.g., north), and 3) beam transmission only during the first 180° rotation after the sync signal; standard "kicking meter" differentiating circuitry (transformer) for converting leading & trailing edge of received E & T tone pulses into short voltage peak pairs (polarity sequence +/- for E, -/+ for T); these + & - peaks are counted separately with 2 electro-mechanical counting devices; stopwatch-type bearing indicator that is reset & started manually or automatically based on receipt of the omni "north" signal) and stopped automatically by the counters upon detection of the equibeam signal; bearing ( = angle from the sync signal) is difference in number "a" of dots and number "b" of dashes reecived between the sync signal and equisignal beam passage, multiplied by half the number "f" of dots & dashes per 360°, i.e., (a-b)*(f/2).]
180995 CH 1935 --- C. Lorenz A.G. "Sendeanordnung zur Erzielung von Kurslinien mittels zweier verschieden gerichteter, abwechselnd asugesandter Hochfrequenzstrahlungen" "Transmission arrangement for generating course lines bei means of two high frequency fields, alternatingly sent in two different directions"  [standard Lorenz landing beam beacon = vertical dipole + 2 alternatingly switched parallel passive reflectors, E/T = Dot/Dash keying]
180996 CH 1935 --- C. Lorenz A.G. "Verfahren zum Betriebe von Funkbaken" "Process for operating radio beacons" [standard Lorenz landing beam beacon = vertical dipole + 2 alternatingly switched parallel passive reflectors, E/T = Dot/Dash keying, but two sets of outer & inner marker beacons (on front course & back course); to avoid confusion interpreting inverted left/right meter deflection on front course vs backcourse, keying of the reflectors can be inversed, depending on which equisignal course the inbound aircraft is using.]
44879 F 1935 --- C. Lorenz A.G. "Appareil transmetteur pour les ondes électriques et en particulier pour les ondes ultra-courtes" "Transmitter for electrical waves, in particular ultra-short" [A vertical dipole at an appropriate height above ground has a radiation pattern that resembles a torus (ring) that is slightly angled upward, away from the antenna (as opposed to a perfect torus when in free-space), instead of a perfect torus if that dipole were in free space. Likewise, if the dipole pattern is deformed with a vertical deflector. Thus upward angle makes it possible for the same beacon to provide glide path guidance. Localizer beacon placed at standard position (on the landing course-line, beyond departure end, and outside the boundary of the airfield (FD: in those days, airfields were often round, without runways). Lines of constant equisignal field-strength emanate from the beacons antenna system, curve downwards towards ground level over some distance, then curve upward with increasing distance. No radiation straight up (FD: i.e., the "hole" in the torus). Pilot follows equisignal localizer beam inbound at the certain altitude, until intercepting a particular curved constant-strength line (or receiving the signal from a marker beacon placed on the course line), and then descends to landing, ensuring that the indicated signal strength remains constant, i.e., the aircraft follows the associated curved line (glide path). Similar to Kramar/Hahnemann's 1934 US patent 2196674.]
2134535 US 1936 Wilhelm Runge Telefunken GmbH --- "Distance Determining System" [Based on received signal-strength. Method depends on receiver sensitivity and transmitter power. Distance is derived from signal strengths received by 2 antennas installed at the same location but a different heights above ground/sea. In general at VHF and horizontally polarized waves, received field intensity is zero at zero height, and changes in sinusoidal manner with increasing height, due to interference of slanted direct wave and ground-reflected wave (single "bounce"). Path-length difference between those waves is equal to 2x product of the transmitter & receiver antenna height, divided by distance over ground level. Receiver audio level is proportional to square of field strength. For known transmit & receive antenna heights + audio volume ratio of the 2 receive antennas, a formula for distance-over-ground is derived.]
2117848 US 1936 Ernst Kramar C.Lorenz A.G. --- "Direction Finding Method" [D/F antenna and circuitry arrangement to produce 2 alternating/opposed cardioid patterns. Instead of standard arrangement of two loop antennas that are alternately combined with an omni-directional antenna, or of single loop with alternatly used center tap: loop antenna + 2 omni antennas, one of which generates 2x the signal strength as the other and with opposite sign, all 3 antennas coupled to the input tube of the same receiver. The "2x" omni antenna is connected via variable coupling, to create a rotable cardioid. Same antenna is activated with switch, typ. in rythm with 50% on/off duty cycle.]
2170659 US 1936 Ernst Kramar C.Lorenz A.G. --- "Direction Finding Arrangement" [D/F antenna and circuit arrangement, with alternately connecting 2 loop antennas with opposite sense of winding (and directivity), switching controlled by a motorized commutator, aural output and visual indication to pilot/operator (the latter in the form of a signal-strengths comparing indicator per Kramar's 1933 US patent 2044852).]
2141247 US 1936 Ernst Kramar & Heinrich Brunswig C.Lorenz A.G. --- "Arrangement for Wireless Signaling" [References Kramar's 1932 US patent 2028510, which itself is equivalent to Kramars 1932 German "Lorenz Beam" patent 577350, as baseline for the antenna arrangement of 1 vertical dipole + 2 switchable reflectors (FD: resulting plane measures ca. ½λ x ½λ). The physical length of the dipole and the reflectors is reduced significantly (e.g., to 1/8 λ or 1/3 λ), and the associated reduction in electrical length is compensated by adding inductances (FD: "loading coils"). The omni-directional radiation pattern of the dipole is hardly affected by shortening the dipole, as well as by the angles of intersection between the two overlapping beams. If the electrical length of the reflectors is also reduced, and compensated back up to ¼λ or ½λ, the patterns becomes more cardioid than that of the baseline arrangement. (FD: ¼λ spacing must be retained for the reflectors to work as such). Principle of the patent is applicable to directional reception and transmission. ]
734130 RP 1937 Ernst Kramar & Walter-Max Hahnemann C.Lorenz A.G. "Ultrakurzwellen-Sendeanordnung zur Erzielung von Gleitwegflächen" "Arrangement of VHF transmission for generation of glide path planes" [Curved "constant field strength" glide path: curve to be used (FD: steepness & gradient) depends on aircraft type (approach speed, etc.). If beacon beyond departure end of runway, then beam elevation adjusted such that flat bottom of curves coincides with intended touch-down point. More optimal curve(s) obtained when curve bottom coincides with ground level at the beacon location. This requires beacon installation at the intended touch-down point. E.g., 2 UHF beacons with horizontal diople just below ground level at the intended touch-down point (FD: i.e., per Diamond/Dunmore's 1933 US patent 2120241). Straight glide path guidance can be obtained with equisignal beam, e.g., two VHF dipoles below ground (fed in-phase by common transmitter), spaced several wavelengths on the localizer course line. Also see equivalent Hahnemenn/Kramar 1939 US patent 2210664]
816120 FR 1937 Le Matériel Téléphonique S.A. Le Matériel Téléphonique S.A. "Systèmes de guidage par ondes radioélectriques par exemple pour l'atterrissage des avions sans visibilité extérieure" "Radio guidance systems, e.g., for landing aircraft without external visibility" [Antenna arrangement for creating 2 overlapping beams with equisignal zone, front-course only, no significant back-course beams (i.e., 1-course, not 2-course pattern). Hence, no ground & obstacle reflections from the back-course emissions. arrangement with vertical dipole + reflector at ¼λ + 2nd vertical dipole (or director) at ½λ + side-reflector at ¼λ, transmitter located behind the reflector (in the now suppressed back-course zone). Two such arrangements to obtain the 2 overlapping beams. Vertical (glide path) guidance via standard visual/instrument method (curve of constant field-intensity), enhanced with device that converts signal strenght to audio tone frequency, hence, deviation from constant field-strength curve changes the audio pitch.]
2147809 US 1937 Andrew Alford Mackay Radio & Telegraph Co. --- "High frequency bridge circuits and high frequency repeaters"  [transmission-line bridge to combine two tone-modulated RF signals with same carrier frequency; used on 90/150 Hz Localizer and Glide Slope systems]
705234 RP 1937 Ernst Kramar & Dietrich Erben C.Lorenz A.G. "Sendeanordnung zur Erzeugung von geknickten Kurslinien" "Arrangement for generating angled/bent course lines" [In the standard configuration of equisignal beam beacon with 1 vertical dipole + 2 alternately switched vertical reflectors (FD: i.e., "Lorenz Beam"), is with reflectros spaced symmetrically left & right of the dipole. Resulting radiation pattern has 2 equisignal beams that point in opposite directions. Beam directions can be shifted to obtain angles other than 180°/180° ((FD: this is referred to as "course bending"), by spacing the reflectors asymmetrically with respect to the dipole. Extreme case of using dipole with single reflector also has this effect, but makes equisignal beam unsharp. Alternative configuration is vertical dipole with symmetrically spaced reflectors, but reflectors of unequal length, one ½λ and the other < ½λ (FD: i.e., 1 reflector + 1 director).]
720890 RP 1937 Ernst Kramar & Werner Gerbes C.Lorenz A.G. "Anordnung zur Erzeugung einer geradlinigen Gleitwegführung für Flugzeuglandezwecke" "Arrangement for generating straight glide path guidance for aircraft landing purposes" [Curved "constant field-strength" beacon glide paths are generally (too) steep on approach and (too) flat near ground, resulting in (too) high landing speed and associated extended floating before actual touch-down. (FD: also require constant power controls and pitch angle adjustments by pilot, instead of stabilized approach, which is highly undesirable and bad practice). A (near-)straight glide path guide beam can be obtained with an upwardly angled equisignal beam (of two vertically overlapping complementary keyed beams, instead of using curves of horizontally overlapping beams). Optimal equisignal beam elevation angle is ca. 3°. High sensitivity for glide path deviation indication requires very sharp/directive sub-beams. For practical antenna system dimensions, this implies UHF radio frequencies (freq. > 300 MHz = wavelenghts < 1 mtr); multiple equisignal beams (at separate elevation angles), separated by sharp nulls, are obtained when antenna system placed several wavelengths above ground. No problem, if always intercepting the equisignal beams from below. So far, nothing new. Proposed antenna configuration: two stacked vertical collinear dipoles. A/N keying makes it possible to identify the multiple glide slope (GS) beams, as the "A" & "N" sub-beams are above/below the lowest GS beam, below/above the next (steeper) GS beam, etc. Same beam patterns can also be obtained with a single vertical antenna that is several wavelengths long (FD: to obtain pattern with multiple lobes), the electrical length of which is cyclicly momentarily slightly increased in the standard complementary keying rythm. Also see Kramar's 1938 US patent 2297228]
2215786 US 1937 Ernst Kramar & Walter Max Hahnemann C.Lorenz A.G. --- "System for landing airplanes" [Partial continuation of Kramar/Hahnemann's 1934 US patent nr. 2196674. Known is VHF beacon with upwardly-angled omni-directional torus-shaped radiation pattern, creating constant-signal-strength glide path curves. This required constant transmitter output and constant receiver gain during the landing phase. Patent proposes using one or more marker beacons, with narrrow pattern across thee approach course line, to indicate glide path intercept planes, and starting point for following constant-signal-strength glide path. (FD: no significant expansion of the referenced 1934 patent).]
2226718 US 1937 Ernst Kramar & Walter Max Hahnemann C.Lorenz A.G. --- "Method of Landing Airplanes" [Continuation of Kramar/Hahnemann's 1934 US patent nr. 2196674 and their 1937 US patent 2215786. ]
767399 RP 1937 Ernst Kramar & Joachim Goldmann C.Lorenz A.G. "Verfahren zur Erzeugung einer vertikalen Leitebene" "Method for creating a vertical guidance plane" [Method for long-range navigation; standard beacon with two complementary-keyed (e.g., A/N) overlapping beams with associated equisignal beam course-line, operating on Longwave or VHF frequencies, suitable for short-range; very long range navigation (great-circle) requires short-wave frequencies; on short-wave, radio waves propagate as groundwaves and skywaves. The latter are refracted by E &amp; F layer in ionosphere, depending on wave elevation angle and frequency. At the receiver station, these various waves combine / interfere; associated phase differences cause periodic fading and A/N distortion, affecting apparent course line. Solved with elevated directional beams (3 parallel vertical dipoles one 1 line + 2 reflectors on perpendicular line through center dipole), such that received skywave is always stronger than the groundwave. Antenna arrangement can be made azimuth-rotable. References Hahnemann's 1924 German patent 474123, Yagi's 1926 German patent 475293, and LMT Co.'s 1937 French patent 816120.]
2206463 CH 1938 --- C. Lorenz A.G. "Sendeanordnung zur Erzielung von Kurslinien" "Transmission arrangement for generating course lines" [Simplified Lorenz landing beam system; vertical dipole with single periodically activated parallel passive reflector.]
731237 RP 1938 Ernst Kramar C.Lorenz A.G. "Empfangsverfahren für Leitstrahlsender" "Method of reception of guide beam beacons" [Method for obtaining simultaneous aural & visual indication regarding equisignal beam of beacons with two overlapping-beams that are complementary-keyed with two different modulation tones. At receiver, the 2 tones are separated with 2-channel filter unit, rectified and fed to a comparing visual instrument. Beacon also broadcasts its keying signal via separate modulaton frequency. This is also received, and used to drive a commutating relay (i.e., synchronized to the beacon keying) for passing the filtered received tones to circuitry that generates their harmonics that are modulated such that the 2 complementary keyed tones now have the same audio frequency (i.e., as if the beacon was a standard 1-tone complementary-keyed one), and fed to the headphones. Also see Kramar's equivalent 1939 US patent 2255741]
206464 CH 1938 --- C. Lorenz A.G. "Rotierende Funkbake" "Rotating radio beacon" [Motorized rotating antenna arrangement of 2 pairs of vertical antennas (grounded monopoles or dipoles) at corners of a square, Adcock arrangement, simultaneously fed by transmitter via , central vertical monopole, fed simultaneously by same transmitter; creates rotating equi-signal beams; using shortwave to obtain long range]
767522 RP 1938 Ernst Kramar & Felix Gerth & Joachim Goldmann & Heinrich Brunswig C.Lorenz A.G. "Empfangsvorrichtung zur Richtungsbestimmung mittels rotierender Funkbake" "Receiving device for determining direction with a rotating radio beacon" [Rotating-beam beacon with omnidirectional north-signal pulse and rotating minimum/null; mentions optical device with synchronously rotating light bulb (inaccurate, complicated construction) and CRT display (Braunsche Röhre) showing pip upon receipt of max signal]
711673 RP 1938 Ernst Kramar C.Lorenz A.G. "Gleitweglandeverfahren" "Glide Path Landing Method" [The curved/parabolic constant-field-strength VHF glide paths are too steep at altitude and too flat near ground (with high engine power setting, resulting in floating down the runway due to high speed), which cannot be done with all aircraft type. Beam method provides (near-)straight glide path (FD: i.e., glide slope), allowing descent to landing with constant descent rate ( = constant vertical speed), and round-out (UK) / flare (US) with idle engine(s). This is achieved with a beacon that has a heart-shaped horizontal radiation pattern (heart-tip at the antenna system), angled towards the inbound approach direction (line hearth-tip / heart-dip crossing the approach track outside the airfield perimeter). Radiation pattern obtained with 2 vertical antennas, spaced 3.87λ or 1.95λ, fed 180° out of phase. Also see Kramar/Hahnemann's equivalent 1938 US patent 2241907, and Kramar's 1939 German 1-course expansion patent 2241915]
2212238 US 1938 Frederick A. Kolster Int'l Telephone Development Co. (part of Int'l Telephone & Telegraph Corp. (ITT), the parent company of C. Lorenz A.G. since 1930) --- "Ultra short wave course beacon" [100% copy of the Lorenz A/N with dipole & switched reflectors landing beam system, with operating frequency increased to higher VHF [30-150 MHz, vs. 30 MHz for standard Lorenz A/N system], so as to avoid night-effect / ionospheric distortions (but susceptible to reflections from terrain and man-made structures), with an added colocated beacon with figure-of-8 pattern for wide-angle approximate location by aircraft far from primary course lines]
2282030 US 1938 Henri Busignies Henri Busignies --- "System of Guiding Vehicles" [Ground-based D/F apparatus comprising 2 sets of 3 antennas (1x 3 orthogonal loops, 1x 3 orthogonal crossing dipoles), eliminating night effect and aircraft effect (transmitting with trailing antenna = horizontally polarized); 2 antennas of each set are connected via amplifiers to 2 pairs of oscilloscope deflection plates. The remaining antennas are alternately connected to a signal strength indicator via an amplifier.]
2290974 US 1938 Ernst Kramar C.Lorenz A.G. --- "Direction Finding System" [Method of indicating equisignal beam beacon (2 switched directional antennas or 1 omni antenna + 2 switched reflectors) course line deviation, by comparing amplitude of the 2 signals. Standard Visual Indicator (vibrating reeed) for use with non-keyed 2-tone equibeams does not provide acoustic deviation indication, but pilot requires both to be available simultaneously. Existing instruments for equisignal beam aural beacons are based on electrical pulses derived from the flanks of the received tone pulses (rectified tone-pulses ( = DC-pulses) are passed through a transformer ( = inductance), which creates a positive induction pulse for each rising flank of a DC pulse and a negative pulse for each falling flank, the pulse amplitude being proportional to the DC-pulse amplitude ( = relative tone strength). This only works with beam-keying with single elements per side (e.g., complementary E/T keying, with only dots on one side, only dashes on the other). However, with these, it is difficult to assess the course deviation by listening to the combined audio signals (except for very large course deviations, when only one sub-beam is received). Aural interpretation is better with complementary dots & dashes keying patterns where both characters have the same number of dots and the same number of dashes (A/N, D/U, etc.). However, these cannot be used with the existing "kicking meter" indicators. Patent fixes this limitation, by inserting a 2-tone filter + 2nd rectifier stage between the 1st rectifiers and the standard summing moving-coil meter. Filters tuned to the repetition rates of the positive (or negative) induction pulses (i.e., factor 2:1). Hence, meter decaying pulse reflections to one side for "A" and to the other side for "N". This is a co-patent / split-off of Kramar's 1939 US patent 2241915. Also see Kramar's 1931 US patent 1949256, and L.M.T. Co.'s 1937 French patent 816120, p. 99 in ref. 21B.]
2297228 US 1938 Ernst Kramar C.Lorenz A.G. --- "Glide Path Producing Means" [Equivalent to Kramar's 1937 German patent 720890]
2288196 US 1938 Ernst Kramar C.Lorenz A.G. --- "Radio Beacon System" [Equivalent to Kramar's 1938 German patent 731237, with some expansion.]
7105791 RP 1938 Ernst Kramar & Heinrich Nass C.Lorenz A.G. "Sendeanordnung zur Erzeugung von Leitlinien" "Arrangement for producing course guide-beams" [The standard "Lorenz Beam" equisignal beacon configuration ( = 1 vertical dipole + 2 reflectors, per Kramar/Lorenz 1932 German patent 577350) is based on complementary keying of the reflectors, and transmitting continuous single tone via the dipole. Equisignal "visual" beacons continuously transmit 2 overlapping sub-beams with different tones, which allows simpler indicator system. Patent modifies the "Lorenz beam" configuration, by not hard-keying the reflectors, but replacing their keying switches / relays with interruptors / variable capacitors / goniometers that are each driven by seperate motor; one motor with 90 rpm, the other with 150 rpm, resulting in 90 & 150 Hz modulation respectively ( = standard modulation tones of Visual Equisignal Beacons), and constant carrier transmitted via the dipole. However, without further measures, this this results in suppression of the equisignal course-lines! This is fixed by changing the reflector length and reflector-dipole spacing such that the deformed dipole patterns have less overlap. Same result if, instead of dipole & reflectors placed on a straight line, they are arranged as a triangle. Can be used with standard Visual Indicator (e.g., reeds). Also see Kramar/Nass's equivalent 1939 US patent 2238270]
2241907 US 1938 Ernst Kramar & Walter Max Hahnemann C.Lorenz A.G. --- "Landing Method and System for Aircraft" [Equivalent of Kramar's 1932 German patent 711673]
2238270 US 1939 Ernst Kramar & Heinrich Nass C.Lorenz A.G. --- "Radio Direction Finding System" [Equivalent of Kramar's 1938 German patent 710591]
2210664 US 1939 Ernst Kramar & Walter Max Hahnemann C.Lorenz A.G. --- "Radio Direction Finding System" [Equivalent to Hahnemann/Kramar's 1937 German patent 734130 (UHF beacon with horizontal diople just below ground level at the intended touch-down point (FD: i.e., per Diamond/Dunmore's 1933 US patent 2120241).]
525359 GB 1939 Frank Gregg Kear Frank Gregg Kear --- "Improvements in or relating to radio transmitting systems" [Equisignal beam beacon, with antenna configuration comprising 2 omni-directional antennas, spaced ½λ and alternately & complementary keyed in-phase and 180° out of phase, to create 2 overlapping cardioid patterns. Alternatively: 2 separately fed omni-antennas, physically spaced ¼λ, with bi-directional transformer-coupled ¼λ feedline between them (= 90° phase difference); can be generalized for X° physical spacing; antennas fed by transmitter(s) via transformers, either 2 tones (Visual Range) or complementary keyed Aural Range. With this arrangement and resulting sub-beam patterns, contrary to conventional 2-/4-course beacons, there is no need for TO/FROM switching on the indicator, as the same characteristic signal (keying pattern or tone) is always (i.e., for all 4 courses!) on the same side of the equisignal beams when flying FROM (or, conversely, TO) the beacon! Various transmitter / modulator-amplifier / transformer configurations.]
2255741 US 1939 Ernst Kramar C.Lorenz A.G. --- "System for determining navigatory direction" [Equivalent to Kramar's 1938 German patent 731237]
718022 RP 1939 Ernst Kramar C.Lorenz A.G. "Antennenanordnung zur Erzeugung einer Strahlung für die Durchführung von Flugzeugblinlandungen" "Antenna configuration for generating a beam for blind landing of airplanes" [Expansion of Kramar's 1938 German patent 711673]
2241915 US 1939 Ernst Kramar C.Lorenz A.G. --- "Direction-Finding System" [Expansion of Kramar's 1938 German patent 711673. Instead of a 2-course glide path beacon with 2 antennas spaced 3.87λ or 1.95λ and fed 180° out-of-phase, now a 1-course beacon based on same cardioid pattern concept, with 2 linear arrays with 3.87λ or 1.95λ spacing between array centers, each array comprising 4 antennas with ¼λ spacing, and the 2 arrays fed 180° out of phase.]
2272997 US 1939 Andrew Alford Int'l Telephone Development Co. (part of Int'l Telephone & Telegraph Corp. (ITT), the parent company of C. Lorenz A.G. since 1930) --- "Landing beacon system"  [2-transmitter beacon system, one producing landing beam with curved, constant field intensity approach path, the other (also) located on the approach course but displaced in the direction of the approach, its field combining with the first, so as to create a linear (straight) landing path.]
767254 RP 1939 Ernst Kramar C.Lorenz A.G. "Verfahren zur kontinuierlichen Ortsbestimmung eines Flugzeuges längs der Anflugstrecke zu einem Landeplatz" "Method for continuously determining position of an aircraft along a the approach path to an arfield"  [From marker beacon to touchdown, rotating wave interference pattern, one beam with phase modulation, one with unmodulated CW, wavelength at least approach path length, e.g., 900 m or 4 km, located at departure end of runway]
2294882 US 1940 Andrew Alford International Telephone & Radio Mfg. Corp. [subsidiary of ITT] --- "Aircraft Landing System" [methods & means for providing a glide path with antenna location remote from landing runway [FD: beside runway, abeam T/D point]; parabolic/curved GP too steep at higher alt, but correct shap at T/D point; straight GP at higher altitude but too sharp angle at T/D point; patent proposes hyperbolic GP shape that is substantially straight but curved at lower alt; antenna system has symmetrical pattern in opposite directions, i.e., 2 GP's in opposite directions (FD: undesirable, since only 1 can serve a correct T/D point!)
2404501 US 1940 Frank Gregg Kear Frank Gregg Kear --- "Radio beacon system" [VHF rotating-beam radio beacon with, e.g., 200-300 MHz carrier frequency; narrow beam rotates in azimuth at a constant rate (e.g., 12-30 rpm); the 360° azimuth is divided into a fixed number of consecutive arc-segments (e.g., 5° wide), starting with, e.g., north. The odd-numbered segments all have a different-but-fixed modulation tone. No transmission when beam sweeps through an even-numbered segment. E.g., with 5° wide arc-segments, 36 segments each with a distinct tone, interspersed with 36 no-tone segments. A receiver on an abritrary azimuth/course, will receive sequentially 3 tones: the strongest is the tone associated with the arc-segment in which that course lies; this is preceded by the (weaker) tone of the preceding arc-segment and followed by the (weaker) tone of the next arc-segment. Transmitter has tone-modulator with tone stepwise altered by same motor as rotating the directional antenna. Receiver has 3 audio filters with center frequency that is operator-selectable to the tone-combination of the desired & adjacent arc-segments. The tone of the center arc-segment directly drives a signal strength indicator. The other 2 tone filters are both followed by a slow-decay signal peak-capturing circuit, the outputs of which drive a zero-center meter, indicating relative strength (with sign) of the 2 adjacent arc-segment signals. Instrument provides continuous indication of deviation from any selectable course.]
2283677 US 1940 Armig G. Kandoian Int'l Telephone & Radio Mfg. Corp. --- "Localizer beacon" [ILS localizer system, 5 loop antennas, transmission line bridge, 2-tone continuous modulation]. Also see 1951 "Localizer antenna system" US patent 2682050 by A. Alford.
2288815 US 1940 David G.C. Luck Radio Corporation of America (RCA) --- "Omnidirectional radio range" [equivalent to the German UKW-Phasendrehfunkfeuer “Erich”; precursor to the post-WW2 VOR system]
581602 GB 1942 Robert James Dippy Robert James Dippy --- "Improvements in or relating to Wireles Signalling Systems" [invention of the Grid / GEE/ G hyperbolic system; covers GEE pulse-signals receiver & CRT display system design]
581603 GB 1942 Robert James Dippy Robert James Dippy --- "Improvements in or relating to Wireles Systems for navigation" [co-patent to Dippy's 1942 British patent 581602]
2436843 US 1943 Chester B. Watts & Leon Himmel Federal Telephone & Radio Corp. [subsidiary of ITT] --- "Radio Antenna" [UHF directional antenna system with 2 overlapping beams, radiating predominantly horizontally polarized waves, without rear lobes, suitable for operation with a mobile glide path transmitter, lower end of GP changes from straight GP angle to zero; finalization of US patent 2419552 (filed 1 month earlier) with same title, by Leon Himmel & Morton Fuchs]
862787 DP 1944 Joachim Goldmann C.Lorenz A.G. "Antennenanordnung zur Erzeugung von ebenen Strahlungsflächen der Strahlung Null" "Antenna configuration for generating narrow nulls in beam radiation pattern" [Invention of the "Elektra" multiple beam system]
148430 GB 1918 Hugo Lichte Hugo Lichte --- "Improvement in navigation by means of an alternating current cable located in the water" [inductive pilot-cable / leader-cable; also same-date French patent 524960]
163741 GB 1919 William Arthur Loth William Arthur Loth --- "Improvements in the system and apparatus for enabling a movable object to pursue an electrically staked out route in a more precise way than by means of visual points of reference" [inductive pilot-cable / leader-cable system for surface/submerged ships/boats, energized with electrical power with specific rhythms or frequencies.]
423014 DE 1919 William Arthur Loth William Arthur Loth "Empfangseinrichtung auf Fahrzeugen zur Navigation nach Führungskabeln" "Reception arrangement on vehicles for navigation by pilot-cables / leader-cables" [crossing loop antennas and "Telefunken Compass" switched dipoles in star-configuration]
410396 DE 1920 William Arthur Loth William Arthur Loth "Vorrichtung zur Navigierung von Fahrzeugenm insbesondere von Schiffen" "System for navigation of vehicles, in particular of ships" [crossed-loops receiver antenna for inductive pilot-cable / leader-cable system]
2224863 US 1938 Edward N. Dingley Edward N. Dingley --- "Blind landing equipment" [inductive pilot-cable / leader-cable system, cables in or on ground; with equi-signal; supplemented by 1938 US patent 2340282 and its equivalent 1938 GB patent 522345 ]
820319 GB 1950 Brian D.W. White National Research Development Corp. --- "Improvements in or relating to azimuth guidance systems" [aircraft azimuth guidance system; a wire supplied with AC power runs parallel with each side of the runway; the frequency of the supplies are either different or have the same carrier frequency with differing modulation frequencies and two equisignal fields exist along the runway center line; aircraft equipped with pick-up loop(s) to detect EM field and derive position relative to the wire(s) and runway center line.]

Table 3: Selected patents regarding radio direction finding, radio location, radio navigation through WW2


Note 1: due to copyright reasons, this file is in a password-protected directory. Contact me if you need access for research or personal study purposes.

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