MIL-STD-291C
5.4 Pulse coding. For X channels, the pulses shall be coded in pairs with a spacing which shall be 12 ± 0.10 µsec as measured at 50 percent voltage amplitude points from the leading edge of the first pulse to the leading edge of the second pulse. For Y channels, the ground-to-air function spacing shall be 30 ± 0.10 µsec as measured at 50 percent voltage amplitude points
from the leading edge of the first pulse to the leading edge of the second pulse.
5.5 Main reference pulse group. The 15 Hz reference bearing group is called the main reference group: for X channels, it shall consist of a group of 12 pairs of pulses, with the
spacing between pairs established as 12 ± 0.10 µsec; for Y channels, it shall consist of a group of
13 single pulses spaced 30± 0.10 µsec. In each case, the repetition rate of the group shall be
15 Hz ± 0.2 percent.
5.6 Auxiliary reference pulse group. The 135 Hz reference bearing group is called the auxiliary reference group: for X channels, it shall consist of 6 pairs of pulses, with the spacing between pairs established as 24 ± 0.10 µsec; for Y channels, it shall consist of a group of 13 single pulses spaced 15 ± 0.10 µsec. In each case, the repetition rate of the group shall be 135
Hz which shall be synchronized with the main reference group; however, the auxiliary group which would otherwise coincide in time with the main reference group shall be removed so that only the main reference group appears in this position in the final output signal.
5.7 Precedence. Random, identity, and distance reply pulses shall not appear during a main or auxiliary reference group.
5.8 Identification signal. The identification signal shall consist of a series of paired pulses spaced as specified in 3.4, transmitted at a repetition rate of 1350 pulse pairs per second (sec)
and synchronized so that the first pulse of an identity pair shall occur 740 ± 50 µsec after the first pulse of the preceding auxiliary reference group.
5.8.1 Equalizing pulse pair. To preserve a constant duty cycle and to minimize bearing
error during identity signals, an equalizing pair of pulses shall be transmitted 100 ± 10 µsec after each identity pair.
5.8.2 Identity cycle. The random and distance reply pulses shall be replaced by the identity pulses at a recurrence rate of once ever 37.5 sec ± 10 percent. During identity, the beacon code shall be transmitted as dots and dashes (Morse Code) of identity pulses; the spaces between dots and dashes being occupied by distance reply and random pulses. The dots shall be 0.125 sec ±
10 percent; dashes shall be 0.375 sec ± 10 percent. Maximum message length shall not exceed
5.0 seconds.
5.9 Pulse repetition rate. The signal shall have randomly distributed pulses which shall be maintained at a rate of 2700 ± 90 pairs per sec before the reference groups are added; the random pulses shall include any distance replies. The distribution of the random pulse pairs, for no interrogating load, shall fall within the limits shown on Figure 1, for a dead time of 60 µsec.
3
For Parts Inquires call Parts Hangar, Inc (727) 493-0744
© Copyright 2015 Integrated Publishing, Inc.
A Service Disabled Veteran Owned Small Business