NOTE: If the terminals of the input connector
are checked with an ohmmeter, they will show
a direct short. This is normal! The matching
coil in the antenna base puts the entire system
at DC ground, but present a perfect 50 ohm
impedance to rf energy
Choosin
a Site
The 14AVG/WB-s can be mounted on the
ground, on a rooftop or on a mast. When
mounting the antenna more than three feet
above ground, a resonant radial system must
be used, such as Hy-Gain's 14RMQ Radial
System Kit. If the antenna is roof mounted
and the roof space is too small for a radial
system, you can droop the radials over the
edge of the roof at almost any angle without
seriously changing the performance of the
antenna. The radial system must be insulated
from the roof and connected to a good ground
for li
htnin
rotection. See Fi
ure 5.
Basically, the function of radials is to provide
a low-loss return path for ground currents.
The reason that short radials are sufficient.
when few are used, is that at the perimeter of
the circle to which the ground system extends,
the radials are sufficiently spread apart. Most
of the return currents are already in the
ground between the radials rather then in the
radials themselves. As more radials are added,
the spaces between them are reduced and
longer lengths help to provide a path for
currents still farther out.
Since the 14AVQ/WB-S is a multi-band,
vertical antenna, the radial system should be
optimized on the lowest frequency you plan
to use. Higher frequencies will benefit
equally from the ground system, while lower
frequencies will not show as much
im
rovement.
To determine the optimum radial installation
for your 14AVQ/WB-S, you must first decide
what is the limiting factor for your
installation.
For best performance, the 14AVQ/VVB-S
should be ground-mounted clear of building
and other structures. When the antenna is
ground-mounted, a radial system is
sometimes not needed. In most areas, where
soil surface conductivity is poor and a good
ground plane is not possible, lay out ground
radials to improve the efficiency of your
antenna.
1. Cost of radial wires
2. Land available for radials
3. Efficiency of your antenna
Table 1 shows some various ground system
configurations. System A is the least costly
and the least efficient. System F is the most
expensive, takes the most land and is the most
efficient.
There is no need to make radials exactly 1/4
wavelength long for the 14AVQ/WB-S. In
fact, the only case where you should have 1/4
wavelength radials would be for
approximately 90 radials. This differs rather
dramatically from the case of the Ground-
Plane antenna where resonant radials are
installed above ground. Since the radials of a
ground-mounted vertical are actually on, if
not in, the ground, they are coupled by
capacitance or conduction to the ground, thus
resonance effects are not important.
