background image

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).

Summary of Contents for DX-88

Page 1: ...8 Band HF Vertical 80 thru 10 Meters Model DX 88 Instruction Manual ...

Page 2: ...s to Coil Assembly 3 1 10 12 15 Meter Trap Assembly 3 3 Capacitor Assembly 3 3 Attaching Capacitor to Coil Assembly 3 4 17 20 Meter Assembly 3 5 Capacitor Assembly 3 5 Attaching Capacitors to Coil Assembly 3 6 30 Meter Trap Assembly 3 7 Attaching Capacitors to Coil Assembly 3 7 Attaching Upper Radiator Tubes to 30 Meter Trap Assembly 3 8 Installation of Tubing Clamp 3 9 Attaching the Trap Assembli...

Page 3: ...Clamp 3 2 Detail C 1 1 8 x 7 16 Mast Capacitor Clamp 3 2 3 10 12 15 Meter Capacitor Assemblies 3 3 Detail A 13 Capacitor Assembly 3 3 Detail B 16 Capacitor Assembly 3 3 4 10 12 15 Meter Trap Assembly 3 4 Detail A 1 1 8 x 1 Mast Capacitor Clamp 3 4 Detail B 1 1 8 x 7 16 Mast Capacitor Clamp 3 4 5 17 20 Meter Capacitor Assemblies 3 5 Detail A 13 Capacitor Assembly 3 5 Detail A 16 Capacitor Assembly ...

Page 4: ...le 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 t...

Page 5: ... Mast O D Mast not supplied 1 1 2 l 5 8 38 41 mm Wind Survival unguyed 75 MPH 121 kmph Wind Survival unguyed with 160 MK 88 50 MPH 80 kmph NOTE If the terminals of the input connector are checked with an ohmmeter they will show an open THIS IS NORMAL A DC shorting coil may be constructed from information in this manual This coil will also improve the impedance match on the 80 meter band CAUTION Wh...

Page 6: ...TYPICAL VSWR CURVES Cont ...

Page 7: ...s are missing There should be 4 coil assemblies These may be identified by comparing them to Figures 2 4 6 and 7 Make all measurements to the given dimen sions plus or minus not more than 1 8 inch The assembly of the DX 88 will be easier if you read this manual completely through at least twice and follow the recommended directions Allow at least 3 hours for assembly Tools The following tools are ...

Page 8: ...lide this assembly into the 1 x 45 tube Seat the rain cap over the 1 inch tube Repeat this instruction for the other capacitor DO NOT place the caplug on the 7 16 tube at this time Attaching Capacitors to Coil Loosely assemble two pairs of 11 8 x 1 clamps and two pairs of 1 1 8 x 7 16 clamps as shown in Details B and C of Figure 2 Select the 80 40 meter coil assembly Item 14 and attach the capacit...

Page 9: ...el 3 Tube 1 x 45 33 Lockwasher 10 internal stainless steel 14 Coil Assembly 80 40 Meters 34 Caplug 7 16 Black 17 Clamp Mast Capacitor 11 8 x 1 35 Insulator 7 16 x 7 8 spacer 18 Clamp Mast Capacitor 1 1 8 x 7 16 36 Rain Cap 1 26 Bolt 10 24 x 1 2 hex head stainless steel Figure 2 80 40 Meter Assembly Detail C 1 1 8 x 1 Mast Capacitor Clamp ...

Page 10: ... Item 8 3 spacers Item 35 1 rain ap Item 36 and 1 caplug Item 34 Push the spacers onto the 7 16 x 19 tube and adjust so that the top spacer is approximately 10 inches from the top end of the tube and the bottom spacer is near the bottom end of the tube Select a 1 x 13 tube Item 5 7 16 x 16 inch tube Item 9 3 spacers Item 35 1 rain cap Item 36 and 1 caplug Item 34 for each assembly Assemble the 13 ...

Page 11: ...tructions NOTE Disassembly of clamps may be needed to properly install them onto several inside locations on the 10 12 15 meter trap assembly NOTE The edge of each 11 8 x 1 clamp should be flush with the edge of each coil form The rain caps should be pushed completely on each 1 tube and should be flush with the 11 8 x 7 16 clamp Tighten the hardware on these 6 pairs of clamps Push a caplug Item 34...

Page 12: ...16 x 19 tube Item 8 3 spacers Item 35 1 rain cap Item 36 and 1 caplug Item 34 Push the spacers onto the 7 16 x 19 tube and adjust so that the top spacer is approximately 10 inches from the top end of the tube and the bottom spacer is near the bottom end of the tube Select a 1 x 13 tube Item 5 7 16 x 16 inch tube Item 9 3 spacers Item 35 1 rain cap Item 36 and 1 caplug Item 34 Assemble the 13 inch ...

Page 13: ... set later on in the instructions NOTE The edge of each 11 8 x 1 clamp should be flush with the bottom edge of each coil form The rain caps should be pushed completely on each 1 tube and should be flush with the 11 8 x 7 16 clamp Tighten the hardware on these 4 pairs of clamps Push the ca Place a large 16 tubing clamp Item 23 over the slotted end top of this assembly but DO NOT tighten at this tim...

Page 14: ...s onto the coil assembly using the clamps as shown in Figure 7 NOTE The edge of each clamp assembly should be flush with each edge of the coil form Tighten the hardware on these two clamp assemblies Place a 10 tubing clamp Item 22 over the slotted end top of this assembly but DO NOT tighten at this time Refer to Figure 9 Detail A 1 Mast Capacitor Clamp Detail B 3 8 x 1 x 3 8 Mast Capacitor Clamp F...

Page 15: ... x 55 tube Item 2 and the two 6 tubing clamps Item 21 Assemble as shown in Figure 8 Dimensions H and I will be set later on in the instructions Tighten all hardware and clamps except for the middle tubing clamp Push a caplug Item 34 on the top end of the 55 x 7 16 tube Item 2 Figure 8 Upper Radiator Tubes Attached to 30 Meter Trap Assembly ...

Page 16: ...ths tighten the clamp with a 5 16 inch nut driver socket or open end wrench until the tubing will not twist or telescope Figure 9 Tubing Clamps Part Description Fits No Tubing Sizes 358756 Clamp Size 6 1 2 all stainless steel and 3 4 5 16 hex head screw Part Description Fits No Tubing Sizes 358757 Clamp Size 10 all stainless steel 1 5 16 hex head screw Part Description Fits No Tubing Sizes 358758 ...

Page 17: ...Item 25 four 10 lockwashers Item 33 and four 10 24 hex nuts Item 28 Assemble this tube as shown to join the bottom of the 10 12 15 meter trap assembly to the top of the 80 40 meter tuning assembly Tighten all hardware securely Select the base assembly and attach to the bottom of the 80 40 meter tuning assembly using two 10 24 x 13 4 inch bolts Item 25 two 10 lockwashers Item 33 and two 10 24 hex n...

Page 18: ...Figure 11 Connecting Trap Assemblies ...

Page 19: ...e tuned individually to favor a particular part of each band On 30 meters dimension H may be lengthened to lower the resonance or shortened to raise the resonance on each band On the other bands more capacitance tubing pushed in will lower the resonance and less capacitance tubing pulled out will raise the resonance If installed on a rooftop the supplied dimen sions will be accurate only if the RR...

Page 20: ... Sum of Dimension A and B Sum of Dimension A and B 80 40 Meter Trap for 6 9 7 4 MHz 80 40 Meter Trap for 3 5 4 0 MHz Graph 3 Graph 4 Dimension C Dimension D 10 Meter Trap for 27 29 7 MHz 12 Meter Trap for 245 26 5 MHz ...

Page 21: ...raph 5 Dimension E 15 Meter Trap for 20 5 22 MHz Graph 6 Dimension F 17 Meter Trap for 17 5 18 5 MHz Graph 8 Dimension H 30 Meter Trap for 9 5 10 5 MHz Graph 7 Dimension G 20 Meter Trap for 13 5 15 5 MHz ...

Page 22: ...1 11 975 12 100 11 25t 13 570 13 870 13 22 15 100 15 450 15 19t 15 450 15 800 15 19f 17 480 17 700 17 16v 17 700 17 900 17 16t 18 900 19 020 19 16t 21 450 21 750 21 13t 21 750 21 850 21 13 25 600 26 100 26 lit Tropical bands for broadcasting use in designated tropical areas Regional band used only in Europe and Asia World Bands used worldwide World Band extensions Not yet officially authorized but...

Page 23: ...TOP VIEW TOP VIEW Figure 12 DX 88 Overall View ...

Page 24: ...duct near power lines is dangerous For your safety follow the installation directions DO NOT install this antenna near any power lines Not only is it dangerous to put up and take down the power lines could cause excessive noise to be received by the radio connected to this antenna If the DX 88 is installed on the ground a radial system is normally required The minimum recommended radial system con...

Page 25: ...ound Mounted Vertical Antennas by Brian Edward pages 2830 QST magazine June 1985 for more information It is recommended to use copper wire or copperweld wire for the radials The Hy Gain ground radial kit model GRK 88 uses 7 23 Copperweld wire The wires may be soldered to lugs and attached to the bottom of the base bracket If the DX 88 vertical is installed on a garage or house roof a resonant radi...

Page 26: ...23 9 7 24 m 22 17 10 5 43 m 20 17 1 5 21 m 19 16 0 4 87 m 17 13 8 4 17 m 16 13 10 4 23 m 15 11 111 3 63 m 13 11 5 3 47 m 12 10 3 3 12 m 11 9 7 2 92 m 10 9 1 2 77 m Table 3 Resonant Radial Lengths NOTE The radial wire lengths may be adjusted longer or shorter to fine tune the resonant frequency on each band Figure 15 Roof Mounted Radial System ...

Page 27: ...transmitter While using low power less than 200 watts output check the VSWR across each band from 3 5 to 29 7 MHz Record this information for future reference See Table 4 Check the VSWR periodically to ensure proper operation This completes your installation of the Omni DX 88 Service Information If you are unable to resolve your problem or if you need to order replacement parts you should contact ...

Page 28: ...VSWR Meter Date_____________ Date______________ Date____________ Frequency VSWR VSWR VSWR 3 7 000 7 150 7 300 10 100 10 150 14 000 14 200 14 350 18 068 18 168 21 000 21 250 21 450 24 890 24 990 28 000 28 400 28 800 29 600 ...

Page 29: ... 2 179737 Clamp Mast Capacitor 3 8 x 1 x 3 8 2 2 358756 Clamp 6 Tubing stainless steel A 2 2 358757 Clamp 10 Tubing stainless steel l 2 358758 Clamp 16 Tubing stainless steel 3 2 543792 U bolt 5 16 x 15 8 x 2 1 4 2 878541 Parts Pack DX88 Hardware 1 2 500321 Bolt 10 24 x 13 4 hex head stainless steel 6 2 500158 Bolt 10 24 x 1 2 hex head stainless steel 50 2 505266 Bolt 1 4 20 x 3 4 hex head stainle...

Page 30: ...r warranty provided the product is returned postage prepaid to Hy Gain with a personal check cashiers check or money order for 8 00 covering postage and handling 3 Under no circumstances is Hy Gain liable for consequential damages to person or property by the use of any Hy Gain products 4 Out of warranty Service Hy Gain will repair any out of warranty product provided the unit is shipped prepaid A...

Reviews: