MFJ-1742 20 Meter Double Extended Zepp Instruction Manual
2
whole system look like a “long wire” antenna of random length, and the gain
decreases.
The gain of the double extended
zepp is contained in two large
“lobes” at right angles to the
antenna (figure at right). Minor
lobes exist in other directions,
giving the antenna about the same
gain (i.e. 1) as a dipole in these
directions.
Because a double extended zepp is
not resonant at its design
frequency, its input impedance is
complex and very high, so it must
be fed with balanced feedline through an antenna tuner.
Assembly
This antenna comes assembled and ready to install. The lengths of the antenna
wires are quite critical and should not be changed. Nylon ropes are needed to
support the ends of the antenna from suitable structures or trees.
Installation
The best location for this antenna is as high and far away as possible from utility
wires, other antennas, and other structures. It is impossible to find a perfect
location, so the best compromise must be accepted. In order to perform properly
the antenna must be installed as a h
orizontal antenna
,
using two tall supports
separated by more than 85 feet.
Suspend the antenna with at least a 50-pound working load nylon rope or
equivalent strength weather resistant non-metallic rope. Never use wire or wire
core rope to support the ends of any antenna. Attach the rope to the end
insulators through the empty holes.
Try to keep the antenna as horizontal (level) as possible. The antenna should be
at least 35 feet above ground to give acceptable performance and as high as
possible for the best overall performance. The feedline should drop vertically
from the horizontal section of the antenna as far as is practical.
If you are using trees for end supports, be sure to allow enough slack or use
some type of pulley and counterweight system to prevent the antenna
