ANTENNAS 353 
IN PLANE OF THE V 
n=16, a=!I7-S 
IN PLANE t TO V 
N=16, @=17.5° 
FicureE 19. Power distribution for standing-wave V antenna. (Courtesy of IRE ) 
vantage of being insensitive to small changes in 
frequency and at the same time are not so subject to 
corona (breakdown of the air because of large poten- 
tial gradients) as slender antennas are. 
Standing-Wave V Antennas 
This type of antenna (Figure 18) utilizes the 
directive properties of the multi-half-wave antenna. 
Two such elements are combined in a V arrange- 
ment so that the major lobe of each (at angle @ with 
each element) is parallel to the axis of the V. By 
feeding the two halves of the V with currents 
180 degrees out of phase the lobe structure is reversed 
to produce maxima, forward and backward, along 
the axial direction, while the field in the plane 
perpendicular to the axis is greatly reduced. The 
value for angle a is equal to the angle between each 
element and its maximum lobe (see Figure 11). 
Figure 19 gives the (power) radiation pattern for 
n = 16 half-wavelengths. 
The directivity of this antenna system may be 
improved by adding one or more reflectors (see 
text on p.358) The reflector is a V antenna of 
identical type. The legs of the reflector are placed 
parallel to those of the primary V and lie in the same 
plane as the original V. The reflector is set approxi- 
mately \/4 behind the primary V. 
TRAVELING-WAVE ANTENNAS 
Field and Pattern 
A traveling-wave antenna is one in which only 
progressive (or traveling) waves are allowed. Re- 
flected waves are eliminated by terminating the end 
opposite the input point in the characteristic imped- 
ance. See Figure 20. 
The equation of the radiation field, neglecting 
wire losses, is 
607; sin 6 
d 1—cosé 
Ep = in [= (1 — cose) | . (19) 
The major lobes given by this equation are plotted 
in Figure 21, and the major lobe angles with the 
wire 0, are plotted in Figure 22. Angle 0,,, it will be 
noted, decreases with increasing wire length. 
Traveling-Wave V Antenna 
As in the case of the standing-wave antenna a 
pair of lines arranged at a suitable angle with each 
CHARACTERISTIC 
IMPEDANCE 
e— L ———______—_-» 
Ficure 20. Lobe structure for Z = 2) traveling-wave 
antenna in free space. 
other, and carrying traveling waves, can be made to 
produce a directional pattern with fairly high gain. 
The traveling-wave V antenna can be designed 
so that the plane of the V is horizontal and the 
maximum lies in the direction of the axis of sym- 
