MIL-STD-291C
1. SCOPE
1.1 Scope. This standard defines the Standard TACAN Signal. The characteristics and tolerances specified will ensure compatibility of all airborne and ground equipment.
2. APPLICABLE DOCUMENTS (Not applicable)
3. DEFINITIONS (Not applicable)
4. GENERAL REQUIREMENTS
4.1 TACAN channels. The TACAN system shall operate on the frequencies shown in table
I.
4.1.1 Number of channels. There shall be provision of 252 channels, 126 "X" channels numbered 1X through 126X, and 126 "Y" channels numbered 1Y through 126Y. Each channel shall have an interrogating frequency/pulse spacing and reply frequency/pulse spacing as shown in table I. In addition, there shall be provision for 126 pairs of air-to-air (A/A) mode channels as specified in 5.1 and also in table I.
4.1.1.1 Interrogating frequency. The interrogating frequency for the 252 channel TACAN system shall begin with Channel 1 (X or Y) at 1025 megahertz (MHz) and increase in 1 MHz increments until Channel 126 (X or Y) at 1150 MHz is reached. The interrogating pulse spacing shall be 12 microseconds (µsec) for X channels, 36 µsec for Y channels, and 24 µsec for Y mode A/A. (See table I) (NOTE: See 3.4 for definition.)
4.1.1.2 Ground reply frequency. The ground reply frequency for the 252 channel TACAN system shall begin at Channel 1X with 962 MHz (which is 63 MHz lower than the interrogating frequency) and increase in 1 MHz increments until Channel 63X is reached at 1024 MHz. Continuing, Channel 64X will be at ground reply frequency of 1151 MHz (which is 63 MHz higher than the interrogating frequency), and increase in 1 MHz increments until Channel 126X is reached at 1213 MHz. The ground reply pulse spacing for X Channels shall be 12 µsec. For
Y Channels, the ground reply frequency shall begin for Channel 1Y with 1088 MHz (which is 63
MHz higher than the interrogating frequency) and increase in 1 MHz increments until Channel
63Y is reached at 1150 MHz. Continuing, Channel 64Y will be at a ground reply frequency of
1025 MHz (which is 63 MHz lower than the interrogating frequency) and increase in 1 MHz increments until Channel 126Y is reached at 1087 MHz. The ground reply pulse spacing for Y channels shall be 30 µsec. (See table I.)
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