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
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.
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