MIL-STD-291C
(8) t = time in seconds from the corrected position of the 10th pulse of the X-mode main reference group or 15 µsec after the 6th pulse of the Y-mode main reference group. t is computed from the average position of the 12th pulse of each auxiliary reference group.
Tolerances:
f = 15 Hz ± 0.2 percent
For angles of elevation between -45 and +45 degrees
θ = 0.3 degree maximum
0 = 0.3 degree maximum
A = 0.21 ± 0.09
B = 0.21 ± 0.09
Sum of A and B not greater than 0.55
Cross polarization effects up to plus or minus 45 degrees from the vertical and within elevation angles of -45 to +45 degrees must be limited such that θ does not exceed 3 degrees and 0 does not exceed 1 degree.
5.11.1 Harmonic content. At vertical angles from the horizon to 6 degrees above the horizon the root means square (r.m.s.) sum of the second through the sixth harmonics of the 15
Hz modulation component of the radiated signal shall not exceed 20 percent. The r.m.s. sum of the harmonics of the 135 Hz modulation component of the radiated signal shall not exceed 15 percent. The amplitude of modulation components radiated at frequencies of 105 Hz, 120 Hz,
150 Hz, and 165 Hz individually shall not exceed 15 percent nor shall the r.m.s. sum of these components exceed 20 percent.
5.12 Distance reply signal. The distance reply signal shall consist of a pair of pulses transmitted in response to a pair of interrogating pulses. The surface transponder shall be capable of delaying the response, when measured from the leading edge of the first interrogating pulse to the leading edge of the first reply pulse, 50 ± 0.1 µsec and 74 ± 0.10 µsec for X-mode and Y-mode. The user then may select the delay that is applicable.
5.12.1 Reply efficiency. The transponder shall reply with not more than 30 percent countdown to 3300 interrogations per second.
5.13 TACAN interrogating signal. The standard signal, to be radiated and received by the airborne equipment of the TACAN system, shall nominally be vertically polarized. The interrogating signal, radiated by the airborne equipment, shall have the following characteristics:
5.13.1 Radio frequency. The frequency of the transmitter output shall be maintained within plus or minus 0.005 percent of its specified frequency.
5.13.2 R.f. pulse spectrum. The energy contained in an 0.5 MHz band centered on a frequency plus or minus 0.8 MHz from the channel frequency shall be at least 23 db below the
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