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Generally speaking, these antennas should be mounted as high as possible for best performance. Antenna
height will affect the exact resonance point, radiation pattern, and takeoff angle. The higher the antenna, the
lower the takeoff angle to the horizon, which increases the effective range of the antenna.
For DX, the minimum height above ground should be 1/2-to 1-wavelength at the lowest operating frequency.
On the low bands, this height becomes impractical for most hams. For example, an 80m dipole at 70 feet is
about 1/4-wavelength above the ground. This antenna would be good for local and short distance
communications, but not optimal for DX, due to the high takeoff angle and ground absorption. A 40M dipole
at 70 feet is approximately 1/2-wavelength high and is likely to be good for DX and less optimal for local or
short range communications. For more information on antenna design, feedline and radiation angles, consult
a reliable text such as the ARRL Antenna Book.
The antenna, including the 300 Ωfeedline, should also be mounted as far from other structures as possible.
This includes the ends of the wire elements, which are actually the most sensitive part of the antenna. Any
objects, metal in particular, within the near-field radiation pattern can affect the impedance and radiation
pattern of the antenna.
The feedline should also come away from the antenna at right angles for at least 1/2-wavelength for best
performance.
Most installations involve compromises due to local terrain, available supporting structures, or other
restrictions. Do the best you can with what you have.
Multi-Band Center Fed Shortened Dipole using Ladder Line Feedline
The DX Engineering Multi-Band Dipoles include 100 feet of high quality legal limit capable 300 Ω ladder
line. Depending on your specific installation, this feedline will need to be shortened or lengthened. The
optional DXE-LLC-1P Ladder Line Couplers can be used for connecting ladder line together for
lengthening the ladder line.
Also included are two rolls of element wire, a hardware packet and four ring terminals. Two of the ring
terminals accommodate 14 gauge wire and are used for the elements. The smaller ring terminals
accommodate 18 gauge wire and are used for the ladder line.
Unroll the 2 wire elements and the ladder line using a hand-over-hand technique. This will prevent kinks and
allow the wires to lay flat for assembly.
The ladder line feedline should be installed in odd multiple lengths of 1/8-wavelength on the lowest
operating frequency to optimize the impedance presented to the balun over the frequency range of the
antenna. This length can be calculated using the formula shown above Table 1 or use Table 1. DX
Engineering 300 Ωladder feedline has a velocity factor (VF) of 0.88.
If you have excess ladder line, it can be zigzagged while suspended in air, but it can't be closer than a few
conductor spacings to metallic objects and should not be coiled or laid on the ground. If it is necessary to
pass close to a metallic object, twist the line to partially balance the affect on both sides of the feedline.
If you need additional feedline, 100 ft. rolls (part number DXE-LL300-1C) and a convenient line coupler
(part number DXE-LLC-1P) are available from DX Engineering. The line coupler includes a high impact,
insulated splice block, ring terminals and stainless hardware, permitting strong and consistent splices of
ladder line. See Figure 2.