
The Gain of a half-wave dipole (same as above).
The scale is in dBi (decibels over isotropic).
Many people have had success in feeding a dipole directly with a coaxial cable feed
rather than a ladder-line. However, coax is not symmetrical and thus not a balanced
feeder. It is unbalanced, because the outer shield is connected to earth potential at the
other end. When a balanced antenna such as a dipole is fed with an unbalanced feeder,
common mode currents can cause the coax line to radiate in addition to the antenna
itself, and the radiation pattern may be asymmetrically distorted. This can be remedied
with the use of a balun.
2. Antenna Gain Information:
This antenna gain chart shows the maximum theoretical (minus a small allowance for
system losses) gain achievable from arrays of closely spaced co-linear dipole elements.
Dimensions shown are for elements almost touching; the actual heights may be slightly
more due to phasing networks used between the dipole elements.