This web page is here because of the generosity of E.M. who sent me this APX-6.
This unit contains a number of features that have migrated into the present day. I think it's an important milestone device.
The FasTrak Vehicle ID Transponder is an example. This is different from an RFID (Wiki) device in that RFID gets it's power from the interrogation signal, i.e. it has no battery or source of power. Transponders are used in aircraft navigation systems such as ADS-B (Wiki) wjich is a direct decedent of this system.
This relates to the gap between the two challenge pulses and to the number of reply pulses, always separated by 16 us.
No. of Pulses
No. of Pulses
4 digit Octal ID
From: Ref 3, Wiki: IFF-modes, Aviation transponder interrogation modes, Secondary Surveilance RADAR\Interrogation modes,
Identification Friend or Foe (Wiki: IFF) "It uses a transponder that listens for an interrogation signal and then sends a response that identifies the broadcaster." This key idea is that the interrogation signal needs to be something the enemy can not easily generate. If the enemy found a way to trigger a transponder response then that response could be used to target that vehicle. One way that was done was using code wheels that might be changed on a daily basis to modulate the interrogation signal.
This compatible with Secondary Surveillance RADAR (Wiki).Louis Alan Hazeltine (Wiki) - Hazeltine Corporation (Wiki) - Neutrodyne (Wiki) - Hazeltine Corp made Radio & Television sets.
This Selective Identification Feature (Wiki: IFF Mk X) enhances how the transponder responds to the interrogator by adding newer modes than 1, 2 & 3 that include an aircraft 4 digit Octal ID
Squawk code. This is typically assigned by Air Traffic Control, but there are reserved codes for various special situations.
Receive range 960 - 1150 Mc.
2C42 (2C42.pdf)Transmit tube.
"The 2C42 is a three-electrode tube of the disk-seal type designed for stable operation as a plate-pulsed oscillator at frequencies up to 1300 megacycles."
Typical Plate voltage 3,000V.
Typical peak output power 1,750 Watts @ 1050 Mc.
For 1090 MHz Tx, set dial to 650
The Antenna cavity can be set half way between Tx of 1090 and Rx of 1030, or 1060 MHz, Dial = 525
LO is set 60 MHz away from Rx so either 1090 or 970, i.e. Dial = 850 or 100.
The 2C42 and 2C46 have the same outline. These are also known as Lighthouse tubes (Wiki).
NSN: 5960-00-237-2414T/R switching (Wiki) tube.
AF 33(600)37650 July, 1956
"The 1B40 is an Argon filled gas switching tube of the separate cavity type."
Ignition Voltage: 250 volts max.
Keep-Alive Current with 300 Vdc & 0.47 Meg limiting resistor: 180 uA min, 320 uA max.
Leakage Power with 500 Watts @ 1050 Mc peak input power, 1000 PPS, 1.0 us pulse width: 0.7 micro Watts continuous max.
Insertion Loss @ 1080 Mc.: 1.0 dB max.
Photo showing purple glow when biased (Industrial Alchemy - Spark Gap Tubes, Trigger Tubes & Passives - 1B40)
Fig 2 Radioactive. Do not remove from
carton except for use or inspection. Do no handle
Radiation Detectors (ORAU, Radioactive Electronic Tubes: the 1B24 uses Ra226 (Wiki)
One each Electron Tube
Mfd. by BOMAC Labratories Inc.
Date Pkd> 5 56
Fig 3 JAN-CBNQ-1B40
"The 2C46 is a three-electrode tube of the disk-seal type designed for use in a specific cavity for stable local-oscillator service between 1000 and 1200 megacycles."
Typical DC plate voltage: 150 @ 8 to 40 mA.
The GSQ-160 Vietnam era outdoor intrusion detector contains a small explosive charge (Atlas MMS) that will make the unit inoperable if someone tampers with it. This prevents the enemy from using it against us.
Most Sonobuoys use squibs (Wiki) to release spring tension but they are typically just a electrical resistor that is way overpowered and so gets hot and breaks, typically allowing a lanyard to be released.
Impact Switch Patents
2236872 Impact switch, Owen E Grigsby, 1941-04-01, -
2236959 Inertia element operated device, Salmond Hubert Mackenzie, Mathisen Anders, Graviner, 1941-04-01, -
2741674 Impact switch, Eugene D Richard, Army, 1956-04-10, - grenade fuze
Fig 1 Front Panel
Fig 2 Inside Side View
Fig 3 Inside Rear View, center tube missing
V-402 (1B40) Missing (1B40.pdf) & phenolic cap
Fig 4 Inside Front View
Left to Right:
2C42, 1B40, 2C48
This was used with the APX-25 IFF which is basically the APX-6 with the addition of an external KY-95 coder (Vintage Avionics \ AN/APX-25) and the removal of the destruct charges. This was to add the Selective Identification Feature (Wiki: SIF) for use with PPI (Wiki) displays that show the four octal digit squawk code. The Destruct switch has been removed in this version.
This test set is built around the C-2714/APX-44 Control Panel. (Vintage Avionics \ AN/APX-44).
The major sections are:
1. 28 VDC power to the C-2714.
2. An RF section that takes in 1090 Mc from APX-44 antenna, and 1030 Mc from VHF Sig Gen (TS-419: 0.9 to 2.1 GHz) and combines them with a directional coupler. The combined signal is split into 3 paths: (P11) RF output to APM-123 Transponder Test Set Probe-11 (TM 11-6625-6678-12, Ref 7); (J21) demodulated RF to power meter TS-731/URM, (J13) RF output.
3. P23 to APX-44.
This came with an R-13 Aircraft VHF AM receiver with a number of Hazeltine patents. It appears Hazeltine was involved in AM radio and television prior to their IFF work. This makes sense since TV makes use of VHF/UHF and pulse signals for horizontal and vertical synchronization.
TS-1843A/APX Serial No. 2032
Env Cat. ABBAAAE Class 1
Weight 3.0 lbs
Stewart-Warner Electronics Chicago, Ill.
Fig 6 newest date code: 1969
2375418 Fixed loop antenna mounting, Fred E Johnston, Stewart Warner, App: 1943-04-29, W.W.II, Pub: 1945-05-08, -
2407916 Shielded coil, Howard O Berg, Stewart Warner, App: 1943-04-10, W.W.II, Pub: 1946-09-17, - Double tuned IF can.
2423797 High-frequency circuit, Reber Grote, Stewart Warner, App: 1944-01-01, W.W. II, Pub: 1947-07-08, - VHF/UHF,
2499613 Electronic pulse time interval discriminator with maximum interval gate, Norman F Thompson, Stewart Warner, 1950-03-07, - IFF, gas tubes, delay lines,
2502343 Pulse generator, Reber Grote, Stewart Warner, App:1945-07-26, W.W.II, Pub: 1950-03-28, - radio altimeter,
2519603 Navigational instrument, Reber Grote, App: 1945-03-17, W.W.II, Pub: 1950-08-22, - radio astronomy, (Wiki: Grote Reber) - by "sighting" the Sun (even through clouds) you get a navigation application.
2542950 Permeability tuned radio receiver, Alfred W Simon, Jr George L Johnson, Stewart Warner,1951-02-20, - Superheterodyne receiver
2556713 Electronic control circuit, Norman F Thompson, Stewart Warner, App: 1946-05-16, W.W.II, Pub: 1951-06-12, - gas tubes, delay lines, IFF
2587146 Antenna, Irving A Gross, Stewart Warner,1952-02-26, - dipole, fold-up, probably 60 - 470 MHz
2760056 Radio tuning apparatus, Irving A Gross, Stewart Warner, 1956-08-21, -
2760057 Signal duplexing system, John D Johannesen, Navy, 1956-08-21, - T/R switching
2760058 Radio frequency oscillator mounting, Irving A Gross, Stewart Warner, 1956-08-21, - 460 - 470 two way radio front end.
2607890 Variably sensitive frequency discriminator, Petroff Merlin, Stewart Warner,1952-08-19, - electrical dial gauge
2698380 High-frequency transmitter and receiver, Irving A Gross, Stewart Warner,1954-12-28, - 460 - 470 two way radio
2770723 Ultrahigh frequency tuner, Harry C Rowe, Stewart Warner, 1956-11-13, - lighthouse tube, variable donut cavity
2794909 Cathode follower radio frequency amplifier for radio receiver, Howard O Berg, Stewart Warner, 1957-06-04, - for use following a ferrite loop antenna.
2945189 Ultra high frequency tuner, Harry C Rowe, Stewart Warner,1960-07-12, - superheterodyne tuner
3025516 Frequency control system for radio identification apparatus, Irving B Bickler, Stewart Warner, App: 1952-11-03, SECRET, Pub: 1962-03-13, 342/45,455/75 - IFF
Cites 3025516 above
4322729 Interrogator-responsor system for secondary radar devices, Peter Honold, Gerhard Wagner, Siemens AG, 1982-03-30, -
4876545 Adaptive blanking interface apparatus for self-protection jamming equipment employed in conjunction with radar systems, Christopher M. Carlson, Nicholas Deninno, ITT, 1989-10-24, -
4990919 Missile decoy system, David V. Manoogian, 1991-02-05 - protects SAM site from ARMs
5144315 System for accurately monitoring aircraft position during training exercises, Carl E. Schwab, Fred N. S. Goodrich, Cardion, 1992-09-01 - IFF pulses used to locate aircraft on test range.
5223837 Anti-exploitation method and apparatus for controlling aircraft IFF, Sidney J. Grossman, Army, 1993-06-29, - a signal analysis receive looks at the "signature" of the incoming IFF interrogation signal and if valid connects the IFF antenna to the IFF equipment, otherwise a termination is connected to the IFF antenna. This implies that the IFF interrogation signal is not crypto covered and is probably the same as used in commercial aircraft transponders.
5424746 Method and system for monitoring vehicles, Carl E. Schwab, Fred N. S. Goodrich, Cardion,1995-06-13, - IFF pulses used to locate aircraft on test range including getting the aircraft altitude from its transponder.
5822430 System for encoding encryption/decryption information into IFF challenges, Robert Doud, Technical Communications Corp, 1998-10-13, - upgrade to the crypto aspects of the interrogation signal.
6545632 Radar systems and methods, Geoffrey Lyons, Michael Pywell, BAE Systems (Hazeltine), 2003-04-08, - adapting ESM Rx & ESM Tx to work as IFF transponder.
20060262006 Transponder, including transponder system, Geir Vavik, 2006-11-23, - commercial general purpose transponder, not military
20080143558 On-Demand Audio Information System and Method For Air Combat, Tsafrir Ben-Ari, Rafael Advanced Defense Systems, 2008-06-19, -
20110001062 Dynamic optical countermeasures for ground level threats to an aircraft, Carl R. Herman, Stephen C. MORAITES, Lockheed Martin, 2014-01-28, - "A laser beam, having Sufficient intensity to interfere with targeting of a weapon system, is projected from the aircraft over a defined scan pattern at ground level." Where the beam scans is determined by the Black Hawk helicopter attitude.
9103628 System, method, and computer program product for hostile fire strike indication, Stephen C. MORAITES, Shawn McPhail, Donald Sobiski, Lockheed Martin, 2015-08-11, - projects gunfire hit probabilities on various places on a helicopter so that maintenance crews know where to look for bullet holes. An IR camera detects the projectile and predicts its path.
9146251 System, method, and computer program product for indicating hostile fire, Stephen C. MORAITES, Shawn McPhail, Donald Sobiski, Lockheed Martin, 2015-09-29, -
9196041 System, method, and computer program product for indicating hostile fire
EP2914977A4 Electronic countermeasures transponder system,
9632168 Visual disruption system, method, and computer program product, Stephen C. MORAITES, Carl R. Herman, Lockheed Martin, 2017-04-25
9714815 Visual disruption network and system, method, and computer program product thereof, Stephen C. MORAITES, Carl R. Herman, Lockheed Martin, 2017-07-25, -
All the patent numbers on the R-13B (28V) 108 - 135 Mc ARC Receiver are assigned to Hazeltine.The RCA Transponder Test Set TS-1843A/APX does not have patent numbers.
1755114 Unicontrol signaling system, Louis A Hazeltine, 1930-04-15, - TRF broadcast band receiver
1755115 Variable condenser, Hazeltine Louis Alan, Hazeltine Corp, 1930-04-15, - TRF broadcast band receiver
1951685 Peak detector, Harold A Wheeler, Hazeltine Corp, 1934-03-20, - peak detection of AM modulation
1958027 Emission valve modulation system, Harold A Wheeler, Hazeltine Corp, 1934-05-08, - mixer for AM radio
2015327 Electron discharge device, Harold A Wheeler, Hazeltine Corp, 1935-09-24, - five or more electrodes in AM radio mixer tube
2041273 Amplifier (AUtomatic) volume control, Harold A Wheeler, Hazeltine Corp, 1936-05-19, - Wiki: AVC
2041291 Detector circuit, Johnson John Kelly, Hazeltine Corp, 1936-05-19, - improved AVC
2152470 Wave signaling system, John F Farrington, Hazeltine Corp, 1939-03-28, - noise reduction
2480872 Beam tube receiver input, James R Moore, Sec of War, App: 1942-11-28, TOP SECRET, Pub: 1949-09-06, - T/R switching
2498561 Adjustable band-pass selector, Harry J Lipkin, Sec of War, App: 1945-09-06, TOP SECRET, Pub: 1950-02-21, - wide IF BW for accurate pulse timing, narrow IF BW for sensitivity
2554515 Radio ranging system, Leo C Young, Robert M Page, (not assigned), App: 1938-08-06, TOP SECRET, Pub: 1951-05-29, - Pulse RADAR
2597352 Decoding device, Jr Edward F Macnichol, Sec of War, App: 1944-10-10, TOP SECRET, Pub: 1952-05-20, - depends on the time between a start pulse and a data pulse. 12.5 uS mentioned a number of times.
2606282 Pulse transponder, Harry J Lipkin, Sec of War, App: 1945-07-09, TOP SECRET, Pub: 1952-08-05, - "...generally known as beacons. When used for navigation and as . transponders when used for identification pur poses."
2567851 Pulse-blocking circuit, Harry J Lipkin, Sec of War, App: 1945-08-01, TOP SECRET, Pub: 1951-09-11, - tube multivibrtor (flip-flop),
2679043 Beacon receiver, Harry J Lipkin, Grambsch Russel, Sec of War, App: 1946-05-21, TOP SECRET, Pub: 1954-05-18, - concerned with AGC & responding only to the main RADAR lobe.
2679580 Wide band receiver-transmitter, Ware Harold, Sec of War, App: 1945-01-24, Pub: 1954-05-25, - acorn tube, Interrogator Responder Transmitter/ Interrogator Responder Receiver.
2890449 Radio navigation system, Sidney B Pickles, Sven H M Dodington, Stavis Gus, ITT, 1959-06-09, - DME (Wiki) 1025 to 1150 MHz in the same frequency range as IFF and also using pulsed signals.
3296615 Identification and recognition system, Robert M Page, La Verne R Philpott, Navy, App: 1942-01-19, TOP SECRET, Pub: 1967-01-03, - IFF
1801466 Electrical method of and means for observing objects in motion, Townsend Clinton Blake, 1931-04-21, - may be the first case of radio telemetry - aircraft sends propeller turns, receiver integrates these to display distance traveled.
1815045 Radio signaling system, Clarence A Boddie, Richard C Curtis, Westinghouse, 1931-07-21, - aircraft uses radio remote control to turn On/Off airport landing lights
1945952 Radio range finder, Nicolson Alexander Mclean, Communications Patents, 1934-02-06, - Hyperbolic requiring multiple stations, LORAN-A?
1993497 Method and means for reporting interference with vehicles, Joseph A Wells, 1935-03-05, - Truck driver can, by pressing a pedal, transmit the truck ID number to indicate a robbery.
2134716 Measuring speed and distance by radiant energy, Gunn Ross, 1938-11-01, - a Doppler system where frequency conversion is used for speed, and pulse time to travel for distance.
2157122 Warning system for indicating the proximity of aircraft, Francis W Dunmore, US Sec of Commerce, 1939-05-09, - altitude coded Collusion warning system
2165690 Navigation instrument, Warrington C Wademan, 1939-07-11, - Time of Flight?
2168602 Radio-controlled signaling means, Joseph A Hassan, 1939-08-08, - light on roof of police car can be turned on by radio.
2207267 Radio apparatus for detecting aircraft, Plaistowe Donald Leopold, RCA, 1940-07-09, - Tx: TV type raster scan, multiple receivers
2225524 Directional wireless system employing pulses, Percival William Spencer, EMI, 1940-12-17, - "The System described in these specifications is of the type having an auxiliary receiver designed to discriminate in favour of interference and which serves to switch of the main receiver for short periods corresponding to each pulse of interference which exceeds a certain amplitude."
2252083 Radio traffic control, David G C Luck, RCA, 1941-08-12, - "As one of the objects of the invention, means are provided to visually indicate to a dispatcher the bearing of one or more aircraft approaching an airport. Another object is to provide means for identifying an aircraft, and its bearing and altitude with respect to an airport. A further object is to provide means on an aircraft whereby a signal from a rotating beacon at the airport keys an aircraft transmitter which sends signals from the aircraft to a suitable direction indicating receiver located at the airport. A still further object is to provide means on an aircraft for automatically transmitting information identifying the craft, its altitude, and bearing." - an aircraft transponder."
3427612 Air to ground radar target identification system, John Vander Horn, ITT, 1969-02-11, - operator in aircraft hears beep coincident with blip on PPI.
Patent Citations (5)
Cited By (1)
3738593 Sector defense system, F Duvall, Army, 1973-06-12, - uses IFF to screen out friendly planes and sends targeting information for hostile planes.
Patent Citations (7)Cited by:3772688 Secondary radar system, J SmitW Kneefel, 1973-11-13, -
4104630 Vehicle identification system, using microwaves, Norman E. Chasek, AT Comm, 1978-08-01, - lTunnel diode & transistor based ow power transponder for railroad car identification
Patent Citations (11)
Cited By (13)
Citations:4376937 Antenna for primary and secondary radars, Georges Cohen, Thales, 1983-03-15, - waveguide combiner
5001488 Battlefield IFF method and system for its application, Jean-Claude Joguet, LMT Radio Professionnelle, 1991-03-19, -
Citations:5223839 Radar identification, Sidney J. Grossman, Army, 1993-06-29, -
Citations:8049643 Vehicle tracking system for vehicle washing, Pete Ness, DRB Systems, 2011-11-01, - TV based for car wash
1823327 Shielding for radio-frequency amplifiers, William A Macdonald, Fred E Johnston, Hazeltine Corp, 1931-09-15, - cans over the coils in a TRF receiver
2135344 Transposed lead-in, Fred E Johnston, Crosey Radio, 1938-11-01, - twin lead with transposing blocks "Tests demonstrate that the average impedance of a lead-in of twisted wires is in the region of 100 ohms, which makes Such a lead-in unsuitable for direct connection to most types of antenna, and receiver." see Zo twisted pair "...The transposition block lead-in, on the other hand, has an impedance averaging about 500 ohms, which is a value very much more suitable..."
2188970 Electric timing system, John C Wilson, Hazeltine Corp, 1940-02-06, - using lumped delay lines for working with TV pulses. involves pulse to pulse timing.
2327248 Wave-signal translating channel, Nelson P Case, Hazeltine Corp, App: 1942-05-08, W.W.II, Pub: 1943-08-17, - IFF?
2398694 Carrier-wave generating system, Nelson P Case, Hazeltine Corp, - generating correct frequency for given channel, IFF?
2403889 Telemetering system, Toro Michael J Di, Hazeltine Research, App:, TOP SECRET, Pub: 1943-08-24, - maybe to encode the altimeter onto an IFF type system?
2407282 System for indicating mechanical motion, Johnson John Kelly, Hazeltine Research, App: 1941-12-18, TOP SECRET, Pub: 1946-09-10, - goniometer & CRT
2413440 Electronic switch, John F Farrington, Hazeltine Research, App: 1942-05-15, W.W.II, Pub: 1946-12-31, - IFF?
2413451 Ultra high frequency tuning unit, Johnson John Kelly, Hazeltine Research, App:1942-10-03, W.W.II, Pub: 1946-12-31, - TV or IFF?
2413607 Time-delay network, Toro Michael J Di, Hazeltine Research, 1946-12-31, - TV or IFF?
2415359 Wave-signal translating system, Bernard D Loughlin, Hazeltine Research, Priority: 1943-12-31, TOP SECRET, Pub: 1947-02-04, - "This invention relates, in general, to wave-signal translating systems and is particularly directed to coding or secrecy aspects of transponder systems. As used throughout this specification and in the appended claims, the term “transponder system' is intended to describe a wave signal translating system which includes a receiving system and a transmitting system so arranged that a predetermined answer or reply signal is transmitted in response to a received interrogating signal, the reply and interrogating signals preferably comprising radiant-energy wave signals."
2421136 Gain control system for pulse modulation receivers, Harold A Wheeler, Hazeltine Research, App: 1945-06-01, W.W.II, Pub: 1947-05-27, - "...for use in a radio-locating and direction-finding system of the type utilizing pulse-modulated signals ..." "For example, the coded signal may include a pair of pulse components, individually having a rectangular wave form and fixed duration but a time separation that is variable in a code sequence. "
2426454 Electronic switch, Johnson John Kelly, Hazeltine Research, App: 1942-05-27, W.W.II, Pub: 1947-08-26, - IFF? pulse train with variable widths
2426454 Electronic switch, Johnson John Kelly, Hazeltine Research, App: 1942-05-27, W.W.II, Pub: 1947-08-26, - IFF? pulse train with variable widths
2454865 Time-delay network, Toro Michael J Di, Hazeltine Research, App: 1945-06-18, W.W.II, Pub: 1948-11-30, -
2457212 Time-delay network, Toro Michael J Di, Hazeltine Research, App: 1945-06-18, W.W.II, Pub: 1948-12-28, -
2483097 Position indicator for airborne traffic, Mcilwain Knox, Hazeltine Research, App: 1946-09-12, W.W.II, Pub: 1949-09-27, - bearing and altitude of aircraft
2522706 Multiple-reflecting time-delay system, Toro Michael J Di, Hazeltine Research, 1950-09-19, - television
2570805 Signal-translating system, Hazeltine Alan, Hazeltine Research, App: 1946-07-20, W.W.II, Pub: 1951-10-09. -
2589808 Transpondor system, Charles J Hirsch, Hazeltine Research, App: 1946-10-21, W.W.II, Pub: 1952-03-18, - 2 ground stations give position and direction of aircraft. -
Hirsch worked for T.A. Edison up until 1930, patent 1996378 Hum elimination (in AM radio) in his name 1931, then started at Hazeltine Research by 1944.
2462265 Frequency divider, App: 1944-08-16, W.W.II, Pub: 1949-02-22, - related to A-scope RADAR display
2572725 Path-indicating system for Mobile Craft, App: 1946-02-15, W.W.II, Pub: 1951-10-23, - for blind landing
2652194 Electrical Computer, 1953-09-15, - tubes, makes use of the frequency divider, not clear what it's for
2686910 Wave-signal transmitting system, 1954-08-17, - VOR (Wiki)
2640925 Electron discharge signal-sampling device, 1953-06-02, - DME (Wiki)
2754481 Electrostrictive time-delay signal translating device, 1956-07-10, - prior art barium titanate
2827564 Time-delay signal-repeater system, 1958-03-18, - MTI (Wiki)
2996707 Radar control system, 1961-08-15, - DME (Wiki)
2795656 Repeater system, 1957-06-11, - for bipolar signals down to DC, but what application?
3002090 Automatic-gain-control system, 1961-09-26, -
3015689 Color-television camera, 1962-01-02, -
3235806 Signal translating circuit, 1966-02-15, - based on Tunnel Diodes work done at and for RCA, not Hazeltine.
3387299 Lightweight IFF detection system, John H Gutman, Huebscher Herbert, Hazeltine Research, 1968-06-04, - for use on the ground with SAM (Wiki).
2515178 Means for synchronizing detection and interrogation systems, Barchok Donald, Army, App: 1943-10-12, W.W.II, Pub: 1950-07-18, -
2796602 Aircraft identification and location system, Gerard C Hess, Norman H Taylor, Raymond M Wilmotte, PADEVCO Inc, App: 1947-08-08, Pub: 1957-06-18, - 32 patent citations.
3004253 IFF System, Teck A Wilson, Hughes Aircraft, 1961-10-10, -
3750163 IFF System, K Hecker, Navy, 1973-07-31, -
5892478 Adaptive azimuth processing for monopulse IFF interrogators, Leonard A. Moss, Hazeltine Corp,
Agilent E4404B ESA-E 9kHz - 6.7 GHz Spectrum Analyzer
FasTrak Vehicle ID Transponder
Gamewell - Code Wheels
Ref 1. QST Sep 1960: Communication on 1215 Mc. with the APX-6, printed page 30. - converting for use in ham band for AM voice.
Ref 2. QST Feb 1961: Practical Operating HInts for 1215 Mc. printed page 27. -
Ref 3. Army ST 44-188-9 IFF Mark X System and IFF Mark X with SIF, Feb 1962 - Training Manual
Ref 4. TM 11-1160, Radar Set AN/TPX-4, War Dept., 28 Dec 1944, 223 pgs, (pdf) TS-159, - this is an IFF interrogator, not a skin reflection radar. 157 to 187 MHz.
Ref 5. Power Point at jproc.ca: Identification Friend or Foe, Richard M. Trim OBE CEnd FIET, 7 Feb 2007, 57pgs -
pg 13: the system shown is not the APX-6.Ref 6. “Radar Contact!”: The Beginnings of Army Air Forces Radar and Fighter Control, Randall DeGering, 2018, 111pgs (pdf) -
Ref 7. TM 11-6625-6678-12, [NAVAIR 16-30APM-123-1; TO 33A1-3-367-1], Operator and Organizational Maintenance Manual, Test sets, Transponder:
AN/APM-123(V)1 (FSN 6625-948-0071) - Army power cables
AN/APM-123(V)2 (FSN 6625-948-0077) - Navy power cables
AN/APM-123(V)3 (FSN 6625-948-0076) - AF power cables
June 1974, w/ C3 28 March 1977; C2 4 December 1975; and C1 3 December 1974. (Liberated Manuals: TM-11-6625-667-12.pdf)Ref 8. TM 11-487, Electrical Communication Systems Equipment, War Dept, 2 October 1944, 537 pgs (Radio Nerds: TM_11-487_OCTOBER_1944.pdf) - does NOT have APX-1
For checking AN/APX-44, DOD AIMS AN/APX-64 and AN/APX-72. The test set provides coded radio-frequency (RF) interrogation signals to check the transponder set P4610.19B and DSAR 4500.15.
Tx: 1030 MHz @ - 6 dBm
Sidelobe suppression type: 3 pulse
PRF: 230 pps
Pulse output group: 2 (P1 & P3) without sidelobe suppression or (P1, P2 & P3) with sidelobe suppression.
Pulse spacing (P1 & P3):
Mode 1: 2 us
Mode 2: 5 us
Mode 3/A: 8 us
Mode C: 21 us
TEST: 6.5 us
4: Modulation from ext source.
Sidelobe suppression pulse spacing (P1 & P2): 2.0 us
Rx: 1090 MHz
-3 dB bandwidth: 6.5 MHz
Sensitivity: -9 dBm
Gating: only for duration replies
Decoding: Codes 0000 to 7777 including emergency and identity
TS-1809/APM-123 Power Requirements:
AC: 115 VAC 50 - 420 Hz, 0.5 Amp
DC: 28 +/-3 VDC 1.5 Amps
Ch 1. Purpose & Scope
Ch 2. Illustrative Problems
Ch 3. Telephone Station Equipment
Ch 4. Telephone Centrals
Ch 5. Portable AWS Information Centers
Ch 6. Wire & Cable & Construction Information
Ch 7. European & US Cables & Loading Systems
Ch 8. Electrical Protective Equipment
Ch 9. Telephone Line Transmission Equipment
Ch 10. Telegraph Equipment (& TTY)
Ch 11 Facsimile Equipment
Ch 12 Power Equipment - Generators, inverters,batteries, Battery Terminals,
Ch 13 Maintenance Supplies- Test Sets,
Ch 14 Radio Equipment
S1 General -
S2 Tactical Radio Sets for Ground Use - SCR-nnn, BC-nnn,
S3 Fixed Plant Radio Equipment
S4 Antennas & Associated Equipment
TM 11-487C-1 Military Standardization Handbook United States Radar Equipment, 15 Dec 1960, 1531 pgs. (Liberated Manuals: TM-11-487C-1.pdf)
Technical Manuals: AN16-30.2APX6-3Navy APX-7 IFF - C-1040 Control, B-47, B-52 - RC-121D & H and C130 aircraft
Technical Orders: 12P4-2APX6-1, 12P4-2APX6-2, 12P4-2APX6-3, 12P4-2APX6-506, 12P4-2A PX6-5O6B, 12P4-2APX6-506C, 12P4-2APX6-506D
"The primary purpose of Radar Set AN/APX-6 is to enable the airplane in which it is installed, to identify itself automatically as friendly whenever it is properly challenged by suitable equipped friendly surface and airborne radars. Two supplementary purposes of the equipment are:
Two (sic) provide two separate channels for the identification of specific friendly airplanes among many friendly planes, and
to provide means for transmitting a special reply referred to as "emergency".
Technical Manuals: 12P4-2APX7-1, 12P4-2APX7-2, 12P4-2APX7-2C, 12P4-2APX7-2D, 12P4-2APX7-2E, 12P4-2APX7-3, 12P4-2APX7-4, 12P4-2APX7-4C, 12P4-2APX7-14AF APX-25 IFF - Similar to AN/APX-6 and replaced by AN/APX-25A.
Components: RT-279/APX-25, C-1158/APX-25, AT-234/A PX-25, KY-95/APX-25, C-112B/APX-25, MT-362A/AAF APX-25A IFF - The AN/APX-25A is similar to AN/APX-6, and replaces the AN/APX-25. C130, C135, KC135, F105, T-39A & B
TO: 12P4-2APX25-2, 12P4-2APX25-2C, 12P4-2APX25-2E, 12P4-2APX25-2F, 12P4-2APX25-3, 12P4-2APX25-3C, 12P4-2APX25-4C, 12P4-2APX25-501, 12P4-2APX25-501B
Components: RT-279/APX, C-1158/APX, AS-133/APX or AT-234/APX, MT-362A/A, KY-95/APX-25, F-245/APX-25APX-26 IFF - This air-to-air identification system consists of an interrogator and a cooperative transponder operating in the X-band. It is operated in conjunction with a separate radar set, and uses the radar antenna and indicator to display identification information. B-52
Technical Manuals: 12P4-1-1, 12P4-2APX25- Series
Specifications: MIL-C-25341A, MIL-T-25036, MIL-T-25348, MIL-M-25460A, MIL-C-8327A
APX-28 IFF Interrogrator - Interrogator Set AN/APX-28 is an IFF Mark X interrogation set intended for use in interrogating Radar Identification Set AN/APX-6 and presenting visual indication of the range and azimuth of the AN/APX-6 reply source for air-to-air rendezvous of aircraft.
Detailed operation of most of the stages in Interrogator Set AN/APX-28 are similar to the operation of like stages in Radar Identification Set AN/APX-6. The RT-198B/ UPX-7 is identical to the RT unit used in AN/UPX-7. Interrogator Set AN/APX-29A can be used by Air Rescue Service as a replacement for AN/APX-28 equipment
Components: RT-198B/UPX-7, MT-1439/A, C-774A/UPX-7, r IP-219/APX, AS-624/APX, AS-625/APX, SA-314/APX, MT-11B9/U, FT-4O9/UAPX-29A IFF Interrogrator - The Interrogator Set AN/APX-29A is an airborne interrogator-responder to be used in conjunction with Radar Identification Sets AN/APX-6 or AN/APX-25 for air-to-air rendezvous of aircraft.
Interrogator Set AN/APX-29A replaces the AN/APX28 and the AN/APX-29. AN/APX-29A uses components of the AN/APS-10 and AN/ UPX-7
APX-35() IFF Transponder - C-1128 or C-1158;
APX-37 IFF Transponder- C-1128 or C-1158; The transponder set provides for the reception, detection, and decoding of IFF Mark X, interrogation, the coding of IFF Mark X replies, and the transmission of the coded reply.
APX-46(V) IFF Transponder - Transponder Set AN/APX-46(V) is a lightweight airborne IFF equipment consisting of either radio receiver-transmitter RT556/APX-46 or radio receiver transmitter RT-555/APX-46, and coder group control C-1128/APX-25 and transponder set control C-1158/APX. This set provides for the reception, detection, decoding, encoding and transmission of signals in the IFF Mark X (SIF) system.
The AN/APX-46(V) is similar to the AN/ APX-37 in operation. It employs the same control panels as the AN/APX-37
APX-49 IFF Interrogator - The prime purpose of the AN/APX-49 is to challenge the identity of targets that are detected and displayed by Radar Set AN/APS-95 operating with the interrogator set. The AN/APX-49 distinguishes between friendly targets and enemy targets and provides a more detailed recognition of friendly targets for additional security and tactical information.
The AN/APX-49 is used with AN/APS-20B, APS-95 and USQ-25.
ASQ-8 MAD - The AN/ASQ-8 is designed to detect submerged submarines from low-flying aircraft. The presence of a submarine is indicated by deflections in inked trace on the paper chart of a recording meter.
Range: 1000 ft approxASQ-10 MAD -
Components: ID-378/ASQ-8, AM-579/ASA-8, MT-993/ASA-8, C-934/ASA-8, DT-37/ASQ-8, AM-294/ASQ-8, MT-776/ASQ-8, 0-90/ASQ-8, AM-295/ASQ-8, y PP-447/ASQ-8, RD-47/ASQ-8, MT-B30/ASQ-8, C-820/ASQ-8, SA-181/ASQ-8, CN-191/ASQ-8, MX-1361/ASQ-8
Technical Manual: AN16-30ASQ8-3
OA-3369/APX-7 IFF Decoder - Decoder Group OA-3369/APX-7 is a selective identification feature (SIF) decoding equipment designed for use in an airborne Mark X IFF system and is comprised of three units: Pulse Decoder, Video Decoder and Control Indicator. Translation and read out of digital SIF codes are an integral function. Numerical display of code designations for three targets replying from a preset challenge sector is provided. The challenge sector is delimited by controls and circuitry within the Decoder Group units.
AN/CPT-2 Life Raft beacon transmitter - The Radar Set AN/CPT-2 is a self-contained, lightweight beacon transmitter for use in a one (1) man life raft. The radar set has as effective range of from 12 to 18 miles. It operates in the frequency of 176 megacycle (mc).
Related Equipment: The AN/CPT-2 is designed to operate with such equipments as Radio Set SCR-729-A, Radar Set AN/ APN-12, Radar Set AN/APN-10, Radio Set SCR-521, Navy ASE, British MK 11. (Equipment Required but not Supplied) (1) Frequency Meter BC-96-C or BC-906-D; (1) Test Set TS-35; (1) Cathode Ray Oscillograph RCA-158 or equivalent; (2) Battery BA-30 (1.5v); (1) Battery BA-38 or BA-38B (103.5v or 93.6v).
Ref 9. YouTube: OZ1GEO's magnificent radio museum. Part 1, 11:36 - @6:20: APX-6 inside shows 1B40 tube removed.
WHAT is THAT blip on the RADAR ? | How do I know if it is Friend or Foe?, 19:30 - Automatic Target Recognition (Wiki)
Vintage Avionics.nl - APX-6 -
JProc.ca: APX-6 IFF Unit -
File:Hazeltine AN-APX-6 Identify Friend or Foe (IFF) transponder, introduced 1950 - National Electronics Museum - DSC00301.JPG -
APR-1 & APR-4 surveillance receivers.
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