Radio Direction Finding

Background

Huff-Duff (Wiki)

In the movie Castles in the Sky (IMDB) they point out that Robert Watson-Watt worked in the meteorology (weather) (Wiki: MET) branch of the National Physical Laboratory (NPL).  While there he developed a direction finding system utilizing an Adcock antenna (Wiki) combined with a Western Electric model 224 oscilloscope which gave instantaneous bearings to lightening strikes.  This lead to automatic HF DF (Wiki: Huff-Duff).  An advanced version of this system in the Elephant Cage (Wiki: Wullenweber) DF system that has a bearing in a fraction of a second.

This is very different from DF systems that require manual pointing.

Patents by Robert Watson-Watt.
YouTube: The Last Elephant Cage - FLR-9
Sonobuoy Ref 54: Sighted Sub Sink Same: the United States Navy's Air Campaign Against the U-boat, pgae XV has a photo of a CRT based Huff-Duff station.

Operation Rafter (Wiki)

By listening using a very sensitive receiver the LO of a W.W.II vintage receiver can be tuned.  For RAFTER the frequency of the transmitter was known (typically a specific Numbers Station (Wiki).  The sensitive receiver would be tuned to 455 kHz above the transmit frequency (sometimes 455 kHz below).

From the Wiki page: "By accident, one such receiver for MI5 mobile radio transmissions was being monitored when a passing transmitter produced a powerful signal. This overloaded the receiver, producing an audible change in the received signal. Quickly the agency realized that they could identify the actual frequency being monitored if they produced their own transmissions and listened for the change in the Superheterodyne (Wiki) tone."

It's not clear what is learned and how the sensitive receiver is tuned?  Let me know.

Platforms

Ships

The idea of the SE950 was that ships in W.W.II could locate submarines by using RDF. The target signal might be a transmission or from the Local Oscillator (LO) from a receiver leaking out to the antenna.

The YE-ZB system (http://aafradio.org/docs/YE-ZB.pdf) as described in History of Communications-Electronics in the United States Navy, by Howeth,1963 (Ref 2), used 12 azimuth beams each of which sent out a Morse code letter.  An omni directional receiver in a carrier based airplane would know the bearing to the carrier by the letter that was strongest. 
Aircraft: "ZB" UHF adapter for RU receiver.
Aircraftcarrier: rotating YE transmit antenna at top of mast.  Codes tied to Magnetic North, not ship heading.
This system was replaced by TACAN (Wiki).
1820004 Aerial navigation system and method, Kruesi Geoffrey Gottlieb, FED TELEGRAPH CO, 1931-08-18 - a 6 beam system.  

Aircraft

One use for RDF is part of a navigation system where the transmitting beacon location is known.  This might be a low frequency, high frequency, VHF or UHF.  The ARN-89 is an example of a LF-HF RDF system and the Light Weight Beacon is an example of an LF beacon that can be backpacked to a known location.

Another application is the one Robert Watson-Watt first developed, knowing about lightening. The "StormScope" is just such an instrument.

The A-N Low Frequency Radio Range was introduced in 1928.  The Link Trainer was to learn how to use this navigation aid, not to learn to fly.
FAA: Flight Inspection History - checking various radio aids to navigation

The DU-1

This was made by Bendix.  It covers the low and medium frequency bands.

	1892151 Direction finding system, Hyland Lawrence A, Wired Radio Inc, Dec 27, 1932, 342/445, 343/728 - loops & sense whip, switchable unidirectional or bidirectional Note sense antenna (1) used to eliminate ambiguity of loop antennas (6, 7).
	1981884 System for detecting objects by radio, Hyland Lawrence A, Taylor Albert H, Young Leo C, Nov 27, 1934, 342/27, 367/128, 342/453, 340/991, 342/407 - bi-static RADAR, depends on re-radiation rather than reflection since the frequency is much lower than current RADAR systems (i.e. probably HF). Note this is THE first U.S. RADAR patent. It is for a CW system that can not determine distance, only Doppler from a single station.
	2144309 Radio apparatus, Hicks Charles William, Bendix Radio, App: 1935-07-12, Pub: 1939-01-17, 342/443 116/280 342/449 116/302 455/274 -
	2144310 Radio apparatus and method of manufacture, Hyland Lawrence A, Bendix Radio Corp, Jan 17, 1939, 343/842, 343/866, 29/605, 29/602.1, 343/872, 403/270 Note using insulating spacers (5) to keep wires separated from eachother and from the metal tube reduces capacitance which improves operation.
	2159379 Radio antenna, Hyland Lawrence A, Bendix Radio Corp, May 23, 1939, 343/705, 343/872, 123/41.56, 244/1.00A, 343/866 - shielded loop built into a Townend ring (Wiki).  Note even though the cowling is close to the spark plugs, the shielding stops the ignition noise.
	2411198 Radio apparatus, George V Eltgroth , Bendix Aviation Corp, App: 1941-11-07, W.W.II, Pub: 1946-11-19, - looks like the DU-1 Band 1: 200 - 400 Kcs Band 2: 400 - 800 Kcs Band 3: 800 - 1600 Kcs.
	2356922 Direction finding apparatus, George V Eltgroth , Bendix Aviation Corp,App: 1942-04-27, W>W.II, Pub: 1944-08-29, - has motor powered tracking loop, uses thyratron tubes in push-pull (400Hz?) oscillator This is for a system newer than the DU-1 manual loop, maybe the ARN-6 or later systems.

Another use might be when an aircraft is involved in Search And Rescue (Wiki: SAR) where the beacon transmitter is in an unknown location.  Survival Radios such as the PRC-90 transmit on known frequencies so the aircraft direction finder system only needs to operate on a limited number of frequencies.

Modern aircraft ejection seats contain a beacon transmitter, similar to the Vietnam era URT-33.  Also built into aircraft there are locator beacons (Wiki) that are activated by a crash.  Locating a downed aircraft is a problem that's not been solved as of 2015.  The case of MH370 (Wiki) is troubling.  The crash type beacon would be ineffective if a plane crashes into water because it will be under water in a very short amount of time.  Although an improved crash beacon could be made (or probably already exists) that would eject from the aircraft and float to the surface. The ultrasonic Underwater Locator Beacon (Wiki: ULB) only has enough battery life to work for a month.  So in the case of MH370 where the crash location could be in a huge area the battery had gone dead by the time the search location was narrowed.  There needs to be improvement in the ULB.  One area is so that standard Sonobuoys can detect it's signal.  The existing signal was designed for optimum range when a very specialized ULB receiver is used.  But in the case of MH370 where no one knew where to look that's of no value.  But there are a huge number of sonobuoys all over the globe and the related equipment and personnel trained to use them.

There has been talk about live streaming aircraft data so that a plane in trouble would be recognized before it crashed, but that's not practical because if every plane aloft or moving on the ground was streaming data there would need to be a system that could (1) have enough bandwidth and (2) process that large volume of data in real time.  A more practical system would be to put a box between the airplane and Flight Data Recorder (Wiki: Black Box) that would look for signs that a crash was likely.  The problem is if the algorithm is too sensitive there will be a lot of false alarms and if too rigid it may not transmit enough information prior to the crash.  Note this system would probably be put out of action the instant of a crash.

2020 June:  the ADS-B beacons (Wiki) might be the answer if it's possible to have a satellite monitor the oceans?

Here's an idea I sent to the FAA:
"A simple solution might be to make an ADS-B transponder with internal rechargeable battery in an enclosure that's strong enough to contain an internal explosion and or fire caused by it's own battery.  This would allow the crew to turn off it's external power, but not turn off the transponder function.  The battery would be charged from the aircraft electrical system and there would be signal from the transponder if it's battery state was low.  That signal can be monitored both by the crew and anyone receiving it's signal.  The battery needs to have enough capacity so that the beacon can operate for more time than the plane it's in.  Rather than just using the internal battery to replace the normal external power when the external power is off the transponder would go into a mode that depends on internal sensors.  Part of this battery mode would be a signal saying it's on battery power.  If a combination of sensors all say the plane is stopped on the ground then the transponder would turn off it's internal battery, but even then would run if external power was applied."

AAF Radio: DU-1 -

TACAN (Wiki)

The frequency band for TACAN is 916 to 1215 MHz which includes IFF and ADS-B.
Wiki: Transponder, Modes, IFF (used Chain Home radar as trigger,not reliable), IFF2 (pre Magnatron based RADARs), IFF3 (157 - 187 Mhz), the Mk X IFF introduced 1030 Mhz for interrogation and a reply at 1090 MHz.  The separation of 60 MHz means an LO at 1060 gives a 30 MHz IF for both Rx and Tx thus allowing the use of very common 30 Mhz IF equipment, ADS-B, 

Replaced the Ze-ZB system (see ships above).  TACAN systems can be installed on ships or pretty much wherever they are needed. But I'm guessing (2020) that as of the common use of ADS-B beacons and GPS the use of TACAN may decline.

The Wiki mentions there's no provision for stealth or crypto.  That's to say the TACAN can be used by an enemy for their own use, or to attach the TACAN station.

2232096 Radio direction finder, Francis W Dane, 1941-02-18 -
2468109 Direction finder,Avery G Richardson, Arbor G Everhart, Federal Telephone and Radio Corp, 1949-04-26 - motor driven & oscilloscope
3185988 Navigation bearing indicator system, Conrad D Ramalho, Hoffman Electronics Corp,  1965-05-25 - TACAN receiver 

Ground Based

During W.W.II there were HFDF systems called Wullenweber (Wiki) FLR-9, Circularly Disposed Antenna Array or AN/FRD-10 (Wiki).  In these systems which started off using a motor driven high speed scan and later upgraded to solid state beam rotation a very short transmission was all that was needed to get a good bearing to the source.  This eliminated the cover that was provided by burst transmission like the GRA-71 that transmitted a message at 300 Words Per Minute instead of maybe 15 WPM for a manual Morse transmission.

The Army has a number of DF systems to locate enemy ground radio transmitters, for example the PRD-1 HF Direction Finding Radio used in Korea and Vietnam, Radio Receiving Set AN/TRQ-23 which uses the OE-4/GR antenna group.  This system uses a motor drive to rotate the DF antenna and a CRT to provide bearings.

The Drop Zone Assembly Aid System (DZAAS)  is a directional receiver worn on the wrist the points to a package on the ground that's arrived by parachute.

Key, Object & Pet Location Tags are a new class of devices.  Most work in conjunction with a smart phone and can help in locating something.  Most of them do not depend on direction finding, but rather proximity between the tag and smart phone.

I have a couple of Black Boxes that are in machined aluminum boxes with water proof sealing that probably good to very great depths, i.e. they are the most indestructible electronic products I've ever seen.  Not only could a tank drive over them but also they are immune to high levels of shock and vibration.  They transmit a narrow pulse that all my receivers will not receive because a matched detector would require a much wider bandwidth than commercial or military receivers use, so the signal is very stealthy.  I'm sure there's a directional receiver that works with these to help someone find whatever is attached.

Submarines

They can have systems that are similar to the Wullenweber only at much higher frequencies.  This could be used to locate other ocean going vessels or land based radio transmitters.

Missiles

Anti Radiation Missiles (Wiki: ARM) are designed to fly into a source of radiation like would be used on a ground to air weapon system. For example the Shrike and HARM.

Patents

"radio direction finder" exact phrase.
Quick Search for Class  with all years selected. CCL/342/443, also: 342/436
Quick search for Class  with all years selected.  CCL/342/$

GB130490 (Google)  Means for Determining the Direction of a Distant Source of Electro-magnetic Radiation (Wiki: Adcock antenna), Reginald Eaton Ellis (Adcock, Frank (Wiki?)), 1919-08-07, -

2142133

2142133 Radio direction finder, Geoffrey G Kruesi, App: 1933-11-25, Pub: 1939-01-03, 342/436 342/439 - two seat biplane.  flexible shafts for loop rotation and loop tuning as well as radio tuning. What Radio Direction Finder is this.  Let me know. See Army Air Force Radio: SCR-AE-183 and scroll down to: Flight, April 11, 1935, pg 400: An American "Radio Compass"; The Kreusi Type which is the Key Unit in the U.S. Army Air Corps Blind Landing System. Thanks to Mike  KC4TOS for this link. AAF Radio: Bendix 1941 Brochure - SCR-242 (MN-26) 1937 manual - Thanks to Bart, K6VK

Pan Am

See Ref 15: Pan Am, Hugo Leuteritz and Radio Direction Finding -

2166100 Direction finder, Ferris W Sullinger, Pan Am, 1939-07-11, - vertical dipoles

2333688 Distance measuring system, Francis H Shepard, RCA, App: 1937-10-29, Pub; 1943-11-09, 367/95; 73/384; 235/414; 331/64; 331/168; 331/170; 331/174; 342/88; 367/114 - Fig 1 -4 & 7 - 9 audio, Fig 5 & 6 RF.  Plate current depends on distance. This may be the first patent for this simple type distance measurement? Why does the plate current vary with the distance?

Calls patents:
GB252263 - 252,263. Watt, R. A. W. Dec. 3, 1924 - One loop (North-South) connected directly to the vertical deflection plates of a CRT and another (East-West) loop connected to the horizontal deflection plates of a CRT.
GB274344 - 274,344. Pilgrim, G. J. M. Dec. 9, 1926. Adding and subtracting apparatus - Not R.A. Watt
GB280235 - Telefunken Ges. f³r Drahtlose Telegraphie. Nov. 5, 1926, [Convention date]. Vacuum tubes. - a CRT like device with a sector shaped metal target or viewing screen.
GB380385 - 380,385. Directive wireless signalling. BRAILLARD, R., 55, Avenue Beau- Sejour, Uccle, MARIQUE, J., 249, Avenue Brugmann, and SOC. ANON. INTERNATIONALE DE TELEGRAPHIE SANS FIL, 13, Rue Brederode, both in Brussels, both in Belgium. April 2, 1932, No. 9514. Convention date, April 3, 1931. [Class 40 (v).] A direct reading radio compass comprises a mirror galvanometer 9
GB447238 - 447,238. Directive wireless signalling. MARIQUE, J., 36, Avenue Burnard, Uccle, and SOC. ANON. INTERNATIONALE DE TELEGRAPHIE SANS FIL, 13, Rue de Brederode, both in Brussels. Oct. 11, 1935, No. 28155. Convention date, Jan. 4. [Class 40 (v)] Relates to direct-reading radiogomometers of the type in which a Neon-lamp is used to indicate the critical points of maximum or minimum reception.
US1471406 see above.

Cited by 11 patents

2321606 Aircraft navigation instrument, William P Lear, Lear Aviation, App: 1940-05-15, Pub: 1943-06-15, 342/426; 342/443 - Is this the SCR-269/LP-21 or some other manual rotation DF antenna?

Calls:
2254943 see above
2286804 Radio compass, Frederick J Hooven, RCA, 1942-06-16, 342/436; 342/439 - single loop and steer Left-Right indicator.
2279151 see: Radar Warning Receivers\Panoramic (Radio Corp or Labs)
2159754 Tuning element for broadcast receiver sets, Wohlfarth Otto, AEG, 1939-05-23 - "On the other hand, Variometers have been disclosed in the prior art in which changes in in ductance are effected by variation of permeability rather than the shifting of an iron-core. The said change in permeability is obtained by varying the biasing magnetization of the iron coils. For instance, an auxiliary winding wrapped on the iron-core could be connected with a source of voltage existing in the set, the current caused to flow through the said auxiliary winding being regulated by a variable resistance or potentiometer."

Popular Mechanics1931 Planes are Landed by Radio when Fog Hides Field.  "Airplanes can be landed safely by special radio guidance even when dense fog shrouds the field.  Transmitting and receiving apparatus developed by the Bureau of Standards make it possible for the pilot to tell by indicators if he is on the proper course, when he reaches the boundary of the field and if he is sending the ship down at the right angle of glide to make a safe landing.  A visual pointer, actuated by radio beams, shows the proper curve to make at landing and tells if the plane is too high or low for safe approach.  The signal is loud until the boundary is reached and stops when crossing it."

Cites

Publication number  Priority date  Publication date  Assignee  Title

US2156297A *  1936-09-30  1939-05-02  Geoffrey G Kruesi  Radio compass

US2174016A *  1937-04-08  1939-09-26  Pan American Airways Corp  Direction finder

US2184306A *  1936-09-30  1939-12-26  Geoffrey G Kruesi  Radio direction finder - Steer Left-Right

US2208378A *  1938-06-30  1940-07-16  Rca Corp  Continuously indicating radio compass, David G C Luck - CRT

US2213273A *  1936-11-06  1940-09-03  Int Standard Electric Corp  Radio direction finding apparatus, Earp Charles William - CRT no moving parts

GB526658A *  1938-04-13  1940-09-23  Sperry Gyroscope Co Inc  Improvements in or relating to apparatus for indicating the position of objects emitting or reflecting radio beams

US2279021A *    1939-11-30  1942-04-07  Rca Corp  Directional receiver
US2408039A *1941-03-05  1946-09-24  Int Standard Electric Corp  Electronic rotation direction finder, H.G. Busignies - similar to Watson0Watt system, see Background above.

Cited by:
2547028 Direction finding system, Lester L Libby, Cole Eugene,  Federal Telephone & Radio (Standard Telephone & Cable), App: 1946-02-14, Pub: 1951-04-03, - similar to Robert Watson-Watt lightening system.
3105193 Visual frequency indicator for broad band sonar monitor, Robert L Denton, 1963-09-24 - indicates the frequency of sonar pulse less than 100 mS long.

Calls:
2208378 see above
2213273 see above
2263377 System for indicating the direction of propagation of electromagnetic waves, Busignies Henri Gaston, Bac Fernand, International Standard Electric Corp, 1941-11-18, 342/429; 367/120 - spinning antenna and CRT/deflection.  See Background above. Cited by 44 patents.
2380929 Indicating system particularly for the measure of angles, Ahier Jean, Hardy Rene, App: 1941-05-17, Pub: 1945-08-07, 342/429 - CRT electrical commutation
2403727 Direction-finding system, Arthur V Loughren, Hazeltine Research, App: 1941-11-10, Pub: 1946-07-09, 342/436; 342/439 - feeds signals into antennas = complex
2407281 Radiated-signal direction finder, Johnson John Kelly, Harold A Wheeler, Hazeltine Research, App: 1941-12-18, (W.W.II), Pub: 1946-09-10, 342/429; 315/378 - 100 to 156 MHz coverage, CRT display, cited by 15 patents.
2408039 see above.

Calls:
2361436 Radio direction finder, Paul B Taylor, App: 1937-11-18, Pub: 1944-10-31, 342/437; 342/439; 342/448 - CRT
2365118 Electrical apparatus, Strafford Frederick Wentworth, AC Cossor, App: 1941-09-13, Pub: 1944-12-12, 342/432; 343/812 - remove ambiguity w/o sense ant.
2407659 Phase comparison system, Fuchs Morton, Federal Telephone and Radio, 1946-09-17, 342/430 - not clear if manual or CRT?
2427660 Radio direction finding system, Roger B Colton, Rex V D Corput, Eleanor T Watson, App: 1944-06-27, Pub: 1947-09-23, 342/428 - CRT
2474268 Radio-frequency in-phase indicator, Marchand Nathan, Federal Telephone and Radio, App: 1945-07-03, Pub: 1949-06-28, 324/84; 324/85; 342/439; 333/125 - phase comparison
2476977 see above.
2656536 see above.

References

Ref 1 Secret Weapon by Kathleen Broome Williams (ISBN: 1-55750-935-2) - History of HF-DF
Ref 2 History of Communications-Electronics in the United States Navy, by Howeth,1963 (free)
Ref 3 History of the Bureau of Engineering, Navy Department, during the world war, 1922 - about W.W.I

[Part 2 Radio Direction Finder pg 210] - Kolster, Stone Radio & Telegraph, 1916 patent
Ch 22 The Radio Direction Finder, pg 261 -

Ref 4 An instantaneous direct-reading radiogoniometer, R.A. Watson Watt & J.F. Herd, IEE, Vol 64 (1926), pages 596-622 or (611-622) - operated between 200 and 400 kHz. (see: SkyScan Severe Thunderstorm Detector which operates on 700 & 1400 kHz)
Ref 5 Journal of Intelligence History: Shore High-Frequency Direction-Finding in the Battle of the Atlantic: An Undervalued Intelligence Asset - mentions Ref 4 above
Ref 6 Scottish Science Hall of Fame: Robert Watson-Watt (1892-1973): An instantaneous direct-reading radiogoniometer - Page 614 -
Ref 7 FCC Radio Intelligence Division (RID) - historic info - also see Aperiodic receivers on my Radar Warning Receiver web page.
Ref 8 CIA: The U.S. Hunt for Axis Agent Radios - also see my Hollow Nickel Spy Case web page.
Ref 9 The History of the Radio Intelligence Division Before and During World War II, 1940 -  1945(pdf), (Google search page, NSA.pdf)
Ref 10 YouTube: Patrolling the Ether, (echo in sound)
Ref 11 TM 11-487D, Radio Direction Finding Equipment, Jan 1951, (Google), 27 pages.

Type	Manual	Frequency MHz	Receiver	Ant	Unpacked Weight Pounds
CRD-2		0.54 - 30	R-127	4 Verticals	2,959
CRD-3		0.25 - 1.5	R-128	5 Verticals	10,060
SCR-206		0.2 - 18	BC-470	Manual Loop + Sense	383
SCR-255		0.55 - 30	BC-903	Twin Vertical Dipoles on Building	2,974
SCR-291		2 - 20	BC-1147	5ea Crossed "U" Adcocks	6,683
SCR-502		1.5 - 30	BC-1147	2 sets of 5 crossed "U: Adcocks	9,015
SCR-503	TM 11-246 286 pages (2 radios) Precursor to PRD-1	1 - 3 0.1 - 1	BC-973 BC-1003 Stylish	LP-23 LP-33 Manual Crossed Loop + Sense	602
SCR-504		0.1 - 65	BC-792 Suitcase	Built-in	89
SCR-555		18 - 65	BC-1005	Manual Adcock + Sense	1,468
SCR-556		65 - 156	BC-1006	Manual Adcock + Sense	1,453
TC-8		0.015 - 145	BC-342 BC-344 BC-787 BC-794 BC-969	Many on Masts	9,470

Ref 12 Radio Material School, Chapter 3, Aircraft Radio Direction Finders (pdf) - The RDF-1-A has a resonate loop driving the grid of VTa, a wire antenna with a pot feeding VTb with a variable cap connecting the two tube plate circuits and a fixed cap feeding the receiver.  Similar to the DU-n series of 1' OD loops on a box.
Ref 13 Appendix  M.  U.S.  Naval  Radio  Equipment - 4. The Radio Direction Finder: includes SE 950
Ref 14 History of Communications-Electronics in the United  States Navy, 1963 (html, pdf)
Ref 15. YouTube: Pan Am, Hugo Leuteritz and Radio Direction Finding, 1:20:22 -

@46:40: RCA receiver patents - the most early patents were licensed
1050441 Electric signaling apparatus, Reginald A Fessenden, 1913-01-14, - motor driven spark transmitter
1050728 Method of signaling, Reginald A Fessenden, 1913-01-14, - motor driven spark transmitter
1113149 Wireless receiving system, Edwin H Armstrong, 1914-10-06, - one tube radio
1173079 Selective tuning system, Ernst F W Alexanderson, GE, 1916-02-22, - Tuned Radio Frequency (TRF) receiver
1201272 Telegraph and telephone receiving system, Lee De Forest, De Forest Radio Telephone & Telegraph, 1916-10-17, -
1231764 Telephone-relay, Fritz Lowenstein, 1917-07-03, - audio amplifier
1239852 Receiver of electrical impulses, Frederick K Vreeland, Vreeland Apparatus, 1917-09-11, - long pole telephone receiver for spark system
1273627 Method of and means for controlling electric currents or potentials, Irving Langmuir, GE, 1918-07-23, - for controlling AC voltage?
1282439 System for amplifying variable currents, Irving Langmuir, GE, 1918-10-22, - transformer coupled TRF?
1329283 Thermionic amplifier, Harold De F Arnold, WE, 1920-01-27, - physical layout of tube
1349252 Method of and means for utilizing thermionic currents, Harold D Arnold, WE, 1920-08-10, - non-linear tube circuits (detectors)
1377405 Audion-circuit, Forest Lee De, De Forest Radio Telephone & Telegraph, 1921-05-10, - audio amp
1398665 Thermionic amplifier, Harold D Arnold, WE, 1921-11-29, - audio amp
1401121 Mounting for vacuum-tubes, Roy M Allen, WE, 1921-12-27, - socket for 4-pin tube with terminals on one side
1426754 Circuits for electron-discharge devices, Robert C Mathes, WE, 1922-08-22, - a change in the "B" supply has a compensating effect on the grid circuit.
1459419 Multistage amplifier circuits, Edward O Scriven, WE, 1923-06-19, - number of stages selected by switch
1465332 Vacuum-tube amplifier, Arnold Harold De Forest, WE, 1923-08-21, - common B+ supply for multiple tubes
1492000 Thermionic device for wireless telegraphy and telephony, Round Henry Joseph, RCA, 1924-04-29, - physical layout of tube
1537708 Thermionic vacuum tube, Schottky Walter, Siemens, 1925-05-12, - physical layout of tube
1544081 Transmitting intelligence by radiant energy, Frederick K Vreeland, Vreeland Apparatus, 1925-06-30, - CW system
1558437 Electrical discharge apparatus, Langmuir Irving, GE, 1925-10-20, - physical layout of tube
1611848 Wireless receiving system for continuous waves, Edwin H Armstrong, Westinghouse, 1926-12-21, - one tube radio

Ref 16. YouTube: Navigation in the 1940s: The Four Course Radio Range, 10:00 -

Introduction
3:25 take off
4:30 Description of ground based transmitter - 28 MHz,
7:20 In plane with graphic of map location

Ref 17. YouTube: 1941 U.S. Army Air Corps Training Film " Radio Aids To Navigation " 32084, 28"30 -

01:45. There is an aerial view of a radio range station. Graphics are used to show how radio fields are set up at a range station using radiators. A map shows radio range coverage in the U.S.
05:27. The film shows a radio tower and discusses the “cone of silence,” which is located directly above a radio tower
06:50. A pilot sits in the cockpit and adjusts knobs on his radio panel
07:29. Z-type markers are used at a radio range station
08:58. A marker beacon in the plane flashes when a plane flies over the Z-type marker
09:41. A fan marker can also be used as a position marker at a radio range system
10:05. The pilot watches the plane’s marker beacon signaling when it is in range of the fan marker. A pilot dials in his range receiver
12:29. The pilot looks at his radio facilities chart. A graphic is used to show how a pilot adjusts his course based on the signals he receives from a radio beam. The film uses basic animation over an aerial photograph to show how a plane can make minor adjustments while the pilot is trying to determine the correct course
18:00. A pilot adjusts the volume of his radio in the cockpit
18:40. A man in a range station transmits regular weather reports
22:31. The film shows the fifth radio tower of a range station that is for voice transmissions, primarily weather reports. The film then shows the radio compass on the instrument panel
23:29 and its antennae on the exterior of the plane. A man takes off the cover of a loop antennae on the top of an aircraft
24:40. A pilot plots his location on a chart (26:30). The film then shows the new automatic compass panel
26:47. A plane flies over a radio tower of a radio range station, concluding the film.

Ref 18. Allied Analysis of Electronic Transmissions in WWII by Jerry Proc VE3FAB was: "Radio Fingerprinting (RFP) and Tina"

RFP involves measuring parameters associated with the transmitting hardware, like carrier frequency, harmonics, azimuth bearing, chirp, hum, &Etc.  Tina involves measuring the "fist" of a telegraph operator.

Ref 19. RDF to RADAR | The secret electronic battle (1946), (A Record of the work of TRE, Malvern 1942), 41:34 -

@1:50 The Defensive - Chain Home (Wiki, Watson-Watt)
@9:50 IFF (Wiki, APX-6)
@ 11:16 The Defensive: The Night Battle -
@21:05 Sea War, Phase I -
@22:52 Allied Air Offensive - GEE (Wiki)
@25:01 Oboe (Wiki) & H-System & Gee-H (Wiki)
@28:06  H₂S (Wiki) ground scanning radar
@30:18 Airborne Jamming (APT-3 Mandrel (Wiki) v. Freya (Wiki) and Wurzburg (Wiki), Moonshine (Wiki) Fighter v. fighter,
@32:03 Window (Wiki, Chaff)
@32:42  Carpet II jamming
@34:06 Saw War, Phase II - ASV (Wiki: Air-to-Surface Vessel radar), ASV-X X-band radar mounted on swordfish (Wiki) biplanes.
@36:38 D-Day - Rebecca/Eureka transponding radar (Wiki, Drop Zone)

Ref 20. YouTube: The Viet Cong and North Vietnamese Army's Radios of the Vietnam Wars, 1:11:52, KN4R -

Left Jab U-21A (Wiki) with Spinning Spaced Loop - (b.c.- later replaced with the RC-12 Guard Rail (Wiki)

Ref 21. Pronto in South Vietnam -  United States Air force Airborne Radio Direction Finding (ARDF) System South Vietnam 1966  (formerly SECRET) -

The EC-4
Nav Equip: AN/APN-179 Bendix Doppler Computer, C12 compass
ARDF Workstation: X, Y and Z.  (ALR-38 Mini-Mod VHF ARDF)

Sub-references
Project CHECO Southeast Asia Report. Igloo White (Initial Phase) (ADA485055.pdf), 64 pgs, July 1968.
Adsid - bomb shape with fins + fake plant antenna out the tail end
Acoubuoy - cylinder with hemispherical nose
Spike Acoubuoy - longer version of Acoubuoy with pointed nose
Munitions: Grave; XM41 & XM41E, Micro-Gravel/XM45E1, Dragon Tooth/CBU-28 (Wiki: MSQ-77) for seeding sensors
There were many problems, many related to management.

Project CHECO Southeast Asia Report. Southeast Asia Tactical Data Systems Interface (U) (ADA486939.pdf) 74 pgs, Jan 1975

Project CHECO Southeast Asia Report. USAF Reconnaissance in Southeast Asia (1961-66) (ADA486464.pdf)  119 pgs, Oct 1966 - (formerly TOP SECRET/NOFORN) the report mentioned in Ref 21, there are many CHECO reports and Ref 21 did not mention which one.
pg 42 Wild Weasel - See Radar Warning Receivers -
App A: USAF Reconnaissance aircraft in SEA 1961 - 1966
App B: USAF Reconnaissance Losses in SEA
App C: Data on Basic USAF Reconnaissance Equipment in SEA

I. Aircraft: RF-101, RF-4C, RB-57E, RB-66
II. Aircraft Performance: Speed (cruse & Max), Radius, Nav Sys, Coms
III. Sensors: Photo (Aerial Recon): KS-72, KA-56, KA-1, KA-55, KC-1B,KA-2, K-47; IR: AN/AAS-18, RS-7, RECON VI; SLR: APQ-102; Other: APQ-99, ALR-47 (RWR\FLares)
IV. Photo Equipment Data:
V. IR Equipment Data: Reconofax VI 70mm film; RS-7 57mm film, AN/AAS-18 no film
VI. Side-Looking Radar: AN/APQ-102 X-band, 5" film
VII. Forward Looking Radar: TI, Modes: Terrain Following, Terrain Avoidance, Gross Scan, Ground Map - lo alt, Ground Map - hi alt.

App D. USAF Sorties by Project: 6 Jan 1966; Rolling Thunder, Electronic Warfare, Steel Tiger, Blue Tree, South Vietnam, Barrel Roll, Yankee Team.
App E. USAF Sorties by Project: 7 Jan - 31 May 1966: RT, BT, YT, SW (Sky Wave), EW, SV
App F. USAF Reconnaissance SEA Sorties & Targets in 1965
App G. Analysis of Sorties in May 1966
App H. 7AF IPIR Dist List
App I. USAF Reconnaissance Projects in SEA: Able Mable to Yankee Team

Ref 22. EC47.com (Wiki) - Electronic Equipment -  USAFSS History of the 6994th Security Squadron 1 July – 31 December 1966, (1969-07_thru_12_6994th_History_(Web).pdf), 93 pgs, March 1970,
Ref 23. Sigint Chatter - The Radio Security Service (in W.W.II)
Ref 24. The Secret Listeners - Direction Finding (in W.W.II)
Ref 25. Hide and Seek during the Battle of the Atlantic with @USSCod Pt 1, 4:42 - mainly about the Bathythermograph,
Ref 26. Hide and Seek during the Battle of the Atlantic Part 2, 8:06 -

Satellite Based RDF

Poppy

The Poppy satellites (Wiki) were early (1962) ELINT (Wiki) satellites, some of which may have flown in formation.

NOSS

Naval Ocean Surveillance System (Wiki) satellites flying in formation can locate Russian (any) ships at sea.  First launch in 1976.
In the past decade I've read that China has a very similar system that can locate US (any) ships at sea.  That article also stated that China could use the same missiles used for nuclear weapons to launch a missile with a conventional warhead.  This is a problem because at launch we will not know what type of warhead is being used. The time between a ship detecting that the missile is coming straight down and the time the conventional explosive destroys the ship is a few seconds.  Note this is much less warning time that is available when an anti-ship missile approaches from the horizon.  Similar to the ultimate weapon that existed prior to W.W.II.

HawkEYE360

A private company doing RF emitter location using three satellites flying in formation. Covers 144 Mhz to 15 GHz.  This is part of Geospatial intelligence (Wiki).

8952847 System of geographical location of a radio signal transmitter located on the earth's surface, and associated method of distributed interferometry, Christian Peyrotte, Francis Martinerie, Jean-Baptiste THEVENET, Thales, 2015-02-10, 342/424 - the satellites shown in Fig 1 look very much like those shown at: HawkEye360/Technology.

My Related Web Pages

YouTube

Restricted Training Film 1-328, Aerial Navigation, 1942,  28:58  - Airways Flying -

Radios and the the Disappearance of Amelia Earhart and Fred Noonan, 1:27:21 - @34:00 Hooven Loop
2062906 Direction finder, Frederick J Hooven, 1936-12-01, -
2107633 Direction finder, Frederick J Hooven, 1938-02-08, -
2171561 Air navigation and landing system, Frederick J Hooven, 1939-09-05, -
2175025 Radio receiver, Frederick J Hooven, 1939-10-03, - aircraft radio compass
2190787 Radio compass, Frederick J Hooven, 1940-02-20, -
2220904 Radio compass system, Frederick J Hooven, 1940-11-12, -
2327641 Radio compass, Frederick J Hooven, 1943-08-24, -

many patents related to aircraft & radios

Links

The Chum Bucket - Marine Radios - Marine Radio Direction Finders -
USASADF (United States Army Security Agency Direction Finding): Radio Fingerprinting - RFP - identifying transmitters (giving each a serial number).
FAS: PRD-12 - HF/VHF/UHF
An Evaluation of Short-Based Radio Direction Finding 1978 - for VHF EPRIB beacons with analysis of Doppler and other systems
Army: More aerial intelligence systems used during Vietnam War - various platforms and bands
: United States Army Airborne Radio Direction Finding Operations -
General Dynamics: AN/MLQ-44 Prophet-Enhanced SIGINT -
AirVectors: The Wizard War: WW2 & The Origins Of Radar: 10: Radio Navigation Systems -
RDF Products: Literature,  WN-004, A Comparison of the Watson-Watt and Pseudo-Doppler DF Techniques -

page created 5 Oct 2009.