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UPX-14 Long Range Interrogator-Responder IFF/SIF Set - A Long-Range Interrogator-Responder IFF/SIF set built by ?????. The UPX-14 transmits IFF/SIF interrogations and receives replies from aircraft within the host radar's range. The UPX-14 requires a master external encoder and a separate decoder for each operating position/data processor. Typical of the encoder/decoder equipment used in a manual system is the GPA-122 which allows up to 14 decoder units or one for each radar scope. In the SAGE System, the FST-2 Coordinate Data Transmitter supplies the encoder and decoder functions to the UPX-14.

It is possible with the UPX-14 to process information about friendly aircraft (SIF) and to determine if an aircraft is friendly (IFF). SIF information is obtained by interrogating friendly aircraft with a set of two pulses, the space between them determines which of the 4 modes is used. IFF (Identification Friend or Foe}) also known as Mode 4 transmits the two pulses and a classified (a/o 1958) encrypted code train of pulses providing identity information.

UPX-14 Interrogator-Responder IFF/SIF
Mode Int Spacing Reply Codes Users Uses Notes
1 3 us 32 Mil 2-digit 5-bit mission code, cockpit selectable
2 5 us 4096 Mil 4-digit octal unit code set on ground for fighters
can be changed in flight by transport aircraft
3A 8 us 4096 Mil/Civ 4-digit octal id code for the aircraft, set in the cockpit
assigned by the air traffic controller
3C 21 us 1278 Mil/Civ Altitude from aircraft altimeter
4 Encrypted
3-pulse reply Mil Encrypted ID info

UPX-14 Interrogator-Responder IFF/SIF

Element Value Notes
Nomenclature UPX-14
Origins UPX-6
Type SIF/IFF Interrogator-Responder
Technology Tube
Transmit Frequency 1030 MHz
Receive Frequency 1090 MHz
PRF Host radar determined
Range Host radar determined Long
Power 117 V, single phase
50, 60, 400 Cycles
Coder/Decoder External
UPX-14 Controls.

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