Hy-Gain 18AVQII Instruction Manual

308 Industrial Park Road
Starkville, MS 39759
(662) 323-9538 Fax: (662) 323-5803
INSTRUCTION MANUAL
General Description
The Hy-Gain 18AVQII is an omni-directional,
vertical radiator that operates on the 10, 15, 20, 40,
and 80 meter amateur bands. The system will work
against earth ground or a resonant radial system
when mounted above ground. You can make your
own radial system following the manual, or use the
Hy-Gain RRK-88 Radial System Kit available at
your Hy-Gain dealer.
The antenna can be used for either Phone or CW
with either a ground or roof mount. It can also be
tuned to mid-band for use with either Phone or CW.
In either case, the SWR bandwidths of the antenna
are broad enough that the antenna will operate at an
SWR of 2:1 or less on the 10, 15, 20 40 and 80-
meter bands. The 18AVQII is supplied with
stainless steel hardware and element clamps for all
electrical and most mechanical connections.

Theory of Operation

The use of heavy duty "Hy-Q Traps" provides
automatic band selection. The Hy-Q Traps are
parallel resonant circuits that isolate the various
sections of the antenna and give quarter wavelength
resonance on all bands. The top-loading coil is used
for operation on the 80-meter band while the overall
height of the antenna remains less than 20 feet.
WARNING: When installing your antenna, take
extreme care to avoid any accidental contact with power
lines or overhead obstructions. Failure to exercise this
care could result in serious or fatal injury.
Lightning Protection
For maximum lightening protection we recommend
the use of a lightening arrestor installed on the feed-
line along with a properly installed ground rod.
Model 18AVQII
Five Band Vertical Antenna
10, 15, 20, 40, 80 Meter
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.
However, it presents a 50-ohm load impedance to
RF energy.
Choosing a Site
The 18AVQII can be mounted on the ground, on a
rooftop, or on a mast. The antenna must be secured
using non-conducting guy ropes. When choosing an
installation site be sure to allow sufficient space for
these guy ropes.
Radial System and Grounding
For best performance, the 18AVQII should be
ground-mounted, clear of buildings 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.
When mounting the antenna more than three feet
above ground, a resonant radial system must be
used, such as Hy-Gain's RRK-88 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
lightning protection.
Important: This antenna must be guyed for
support. Non-conducting U-V proof guy rope (not
included) should be secured between the tubing
clamps (item #17) located below the 80-meter
loading coil shown in Figure 2. The ends of the
guys should be sufficiently anchored to the ground
with stakes or another sturdy support.
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