CHAPTER I
GENERAL DESCRIPTION
ELECTRICAL DESIGN
The Hy-Gain DX-88 is an omnidirectional, unity
gain, self supporting vertical antenna that
operates in the Amateur 10, 12, 15, 17, 20, 30,
40, and 80 meter bands. This vertical antenna
may also be tuned to provide outstanding
reception in the SWL 11, 13, 16, 19, 22, 25, 31,
41, 49, 74, and 90 meter bands. The DX-88 will
work against an earth ground and a set of ground
radials or a resonant radial system when
mounted above ground. You may construct your
own radial system from information in this
manual, or you may purchase the optional
ground radial kit for the DX-88, Model GRK-88,
Order No. 189S, or the resonant roof radial kit,
Model RRK-88, Order No. 1905.
An optional 160 meter kit, Model 160 MK-88,
Order No. 191S, is also available for the DX-88
vertical. The 160 meter kit is only recommended
for ground-mounted installations.
Dimensions are included in this manual for op-
timization on either the CW or phone portions of
the 80, 40, and 20 meter bands. Regardless of
the optimization, the VSWR bandwidths of the
DX-88 are broad enough for the antenna to
operate at a VSWR of 2:1 or less on the 10, 12,
15, 17, and 30 meter bands. The bandwidth on
80 meters is approximately 50 KHz at 2:1
VSWR, because it is inductively loaded on this
band. The bandwidth on 40 meters is
approximately 200 KHz, and on 20 meters
approximately 250 KHz.
The Omni DX-88 vertical antenna features stain-
less steel hardware for all electrical and most
mechanical connections. The DX-88 also
features heavy-wall 1 3/8 inch and l 1/8 inch
aluminum tubing for high strength and large
diameter #12 copper wire coils for low loss and
high-Q performance.
A high-efficiency non-automatic band-switching
kit is available to add 160 meter operation to the
DX-88, Model 160 MK-88, Order No. 00191S.
The Omni DX-88 vertical antenna utilizes its
entire length for radiation on both 80 and 40
meters.
It resonates on each of these two bands with the
aid of a tuned circuit near the base which looks
inductive in the 3.5 - 4.0 MHz band and
capacitive in the 7.0 - 7.3 MHz band. Adjustable
piston capacitors set the resonance of this tuned
circuit, which affects the amount of inductance
and capacitance, and the resulting antenna
resonances within each band.
The remaining bands are obtained by using low-
loss, high-Q tunable traps to isolate one-quarter
wavelength sections along the radiator. One-
quarter wavelength sections always produce low-
angle radiation patterns without high-angle
lobes. The distances between the traps are fixed
and the traps themselves are tuneable, except for
the 30 meter band. This allows the antenna to
operate on the new WARC bands of 12 and 17
meters as well as the older 10, 15, and 20 meter
bands. This also allows the DX-88 to resonate on
or very close to the international SWL bands,
with the proper adjustment of each trap.
MECHANICAL DESIGN
The DX-88 mechanical design features 0.120
wall, 1 3/8 inch and 1 1/8 inch 6063T832
aluminum tubing for extra high strength. Wind
survivability is 75 MPH WITHOUT guying. The
large diameter coils used in the traps and 80/40
tuning circuit are constructed on large diameter
high strength forms and are protected from
environment by covers made from the same
material. The DX-88 may be disassembled into
sections of less than 55 inches for easy
transportation to DX locations. All stainless
steel hose clamps and hardware are used for all
electrical connections. All insulators and coil
covers are UV protected. The coil covers may be
removed easily for cleaning, modifying or
repairing the coils. When the 160 meter kit has
been added, the wind survivability is 50 MPH
(80 kmph).
