Figure 2-23.—Whip antennas.
capabilities. Power ratings for most whips range from
1 to 5 kW PEP.
WIRE-ROPE FAN ANTENNAS
Figure 2-24 shows a five-wire vertical fan antenna.
This is a broadband antenna composed of five wires,
Figure 2-24.—Vertical fan antenna.
each cut for one-quarter wavelength at the lowest
frequency to be used. The wires are fanned 30 degrees
between adjacent wires. The fan antenna provides
satisfactory performance and is designed for use as
a random shipboard antenna in the hf range (2-30
MHz).
DISCAGE ANTENNA
The discage antenna (fig. 2-25) is a broadband
omnidirectional antenna. The diseage structure consists
of two truncated wire rope cones attached base-to-base
and supported by a central mast. The lower portion
of the structure operates as a cage monopole for the
4- to 12-MHz frequency range. The upper portion
operates as a discone radiator in the 10- to 30-MHz
frequency range. Matching networks limit the vswr
to not greater than 3:1 at each feed point.
Vinyl-covered phosphor bronze wire rope is used
for the wire portions. The support mast and other
portions are aluminum.
VHF/UHF
At vhf and uhf frequencies, the shorter wavelength
makes the physical size of the antenna relatively small.
Aboard ship these antennas are installed as high as
2-14
