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
Winkler, David F., Searching the Skies: the Legacy of the United States Cold War Defense Radar Program, USAF Hq Air Combat Command, 1997, 192 pages, Pdf
