MIL-DTL-85670D
3.6.5 Impedance. The impedance shall be nominally 50 ohms in all bands to operate with a 50 ohm transmitter-
receiver output using 50 ohm aircraft cabling.
3.6.6 Radiation pattern gain. The radiation patterns shall be essentially omnidirectional. The antenna gain pattern
shall be as specified in table II when measured on a 32-foot octagonal ground plane with reference to a vertically
polarized antenna. The gain shall be determined by comparing the amplitude of the signal received by the blade
antenna at its beam maximum with that of a one quarter wavelength monopole (tuned to the frequency of interest) at
its beam maximum. The test shall be conducted on a 32-foot octagonal ground plane. Measured values shall be in
accordance with table II. The established reference gain values of the resonant quarter wave length monopole
antenna when mounted on the 32-foot octagonal ground plane are:
a. +3.5 dBi at 30 MHz.
b.
+4.5 dBi at 50 MHz.
c.
+5.0 dBi at 88, 108, 116, 130, 174, 225, 300, and 400 MHz.
TABLE II. Antenna gain pattern.
Frequency
Minimum gain at Beam Max.
(MHz)
(dBi)
30
-23.0
40
-21.0
50
-20.0
70
-16.0
88
-11.0
108
-8.0
130
-2.5
174
0.0
225
+2.5
300
+4.0
400
+3.0
3.6.7 Power handing capability. The antenna system shall be capable of handling 100 watts average power in the
225 - 400 MHz band, 40 watts average power in the 108 - 174 MHz band, and 40 watts average power in the
30 - 88 MHz band. Duty cycle shall be continuous.
3.6.8 Polarization. The antenna shall be essentially vertically polarized when mounted on a horizontal ground
plane.
3.6.9 Lightning protection. The antenna shall comply with lightning protection requirements of 4.5.4.7 when the unit
is subjected to the current wave form specified in the following test method for direct effects on antennas in zone 1B.
3.6.9.1 Lightning protection test method. The lightning effects which aerospace vehicles experience and the
effects which are reproduced through laboratory testing with simulated lightning waveforms are divided into direct
effects and indirect effects. The direct effects of lightning are the burning, eroding, blasting, and structural
deformation caused by lightning arc attachment, as well as the high pressure shock waves and magnetic forces
produced by the associated high currents. The physical damage to the antenna will be discussed as a direct effect.
Electrical transients induced by lightning due to coupling of electromagnetic fields an indirect effect. These effects
include malfunction or damage to electrical/electronic equipment.
3.6.9.1.1 Lightning attachment zones.
a.
Zone 1. Surfaces of the vehicles for which there is a high probability of initial lightning flash attachment
(entry or exit).
A "B" type region is one in which there is a high probability that the arc will remain attached.
b.
Zone 1B: Initial attachment point with high probability of flash hang-on, such as a trailing edge.
9
For Parts Inquires call Parts Hangar, Inc (727) 493-0744
© Copyright 2015 Integrated Publishing, Inc.
A Service Disabled Veteran Owned Small Business