ASSEMBLY AND INSTALLATION
INSTRUCTIONS
738XB
70 CM OSCAR BOOMER
432-438 MHz
COMMUNICATIONS ANTENNAS
951451 (7/94)
738XB
THIS ANTENNA IS AN ELECTRICAL CONDUCTOR. CONTACT WITH POWER LINES CAN RESULT IN DEATH, OR SERIOUS INJURY.
DO NOT INSTALL THIS ANTENNA WHERE THERE IS ANY POSSIBILITY OF CONTACT WITH OR HIGH VOLTAGE ARC-OVER FROM
POWER CABLES OR SERVICE DROPS TO BUILDINGS. THE ANTENNA, SUPPORTING MAST AND/OR TOWER MUST NOT BE CLOSE
TO ANY POWER LINES DURING INSTALLATION, REMOVAL OR IN THE EVENT PART OF THE SYSTEM SHOULD ACCIDENTALLY
FALL. FOLLOW THE GUIDELINES FOR ANTENNA INSTALLATIONS RECOMMENDED BY THE U.S. CONSUMER PRODUCT SAFETY
COMMISSION AND LISTED IN THE ENCLOSED PAMPHLET.
Your Cushcraft 738XB Boomer antenna is designed and manufactured to give trouble free service. This antenna will perform as specified if the
instructions and suggestions in this manual are followed and care is used in the assembly and installation. When checking the components received
in your antenna package use the parts listed beside each diagram. There is a master parts list on page 2. If you are unable to locate any tube or
component, check the inside of all tubing.
to verify the parts count. If you claim a missing part, you will be asked for the weight verification label.
IMPORTANT: Save the weight label from the outside of the carton. Each antenna is weighed at the factory
WARNING
PLANNING
Plan your installation carefully. If you use volunteer helpers be sure that they are qualified to assist you. Make certain that everyone involved
understands that you are the boss and that they must follow your instructions. If you have any doubts at all, employ a professional antenna
installation company to install your antenna.
LOCATION
Location of the antenna is very important. Surrounding objects such as trees, power lines, other antennas, etc. will seriously reduce efficiency. To
minimize the effects of surrounding objects, mount the antenna as high and in the clear as possible. If metal guy wires are used, they should be
broken with strain insulators. EXTREME CARE MUST BE USED FOR YOUR SAFETY. YOU MUST INSURE THAT WHILE THE 738XB IS IN
OPERATION NEITHER PEOPLE OR PETS CAN COME IN CONTACT WITH ANY PORTION OF YOUR ANTENNA. DEADLY VOLTAGES AND
CURRENTS MAY EXIST. ALSO, SINCE THE EFFECTS OF EXPOSURE TO RF FIELDS ARE NOT FULLY UNDERSTOOD, LONG TERM
EXPOSURE TO INTENSE RF FIELDS IS NOT RECOMMENDED. THERE IS A WARNING STICKER WHICH MUST BE ATTACHED TO THE
BOOM AS SHOWN IN FIGURE G.
MOUNTING
The mast mount bracket will accommodate up to 2" (5.1 cm) mast. A 1-1/2" (3.8 cm) or larger heavy wall mast should be used. A good heavy duty
antenna rotator will provide the best service and longest life.
Mount your 738XB at least 10 feet (3 meters) above the ground so that the antenna may be pointed straight up. The mast should be at a 45 degree
angle to both element planes. Typical mounting is shown in Figure F.
SYSTEM GROUNDING
Direct grounding of the antenna, mast and tower is very important. This serves as protection from lightning strikes and static buildup, and from high
voltage which is present in the radio equipment connected to the antenna. A good electrical connection should be made to one or more ground rods
(or other extensive ground system) directly at the base of the tower or mast, using at least #10AWG ground wire and noncorrosive hardware. For
details and safety standards, consult the National Electrical Code. You should also use a coaxial lightning arrester. Cushcraft offers several different
models, such as LAC-1, LAC-2 and the LAC-4 series
.
ASSEMBLY
Assemble your antenna by following the directions and illustrations in steps 1 through 5. After the antenna is completely assembled, verify
dimensions and element spacings for accuracy.
HOW TO CHECK VSWR
The 738XB does not require tuning after assembly. You may check the VSWR in order to confirm assembly was done properly. The easiest place to
check the antenna is likely to be in its final mounting configuration. Orient the antenna such that it is pointing straight up. The back of the antenna
should be at least 2 feet (0.6m) off the ground.
Run the coax cable from your transmitter to the area in which the antenna is going to be tested. The length of this cable or your feedline is not critical.
Connect a good quality VSWR bridge to the end of this cable. Connect a short length of cable [10 ft. (305 cm) or less] from the VSWR bridge to the
antenna under test. Set the transmitter to your center operating frequency and measure the VSWR while taking care not to effect the measurement
with your body. A VSWR of 2:1 or less is satisfactory and will not degrade the performance. If the VSWR is greater than 2:1, check all dimensions
and connections.
1
738XB
MASTER PARTS LIST
KEY P/N DESCRIPTION QTY
11 010011 8-32 stainless steel hex nut 36
26 190026 7/8" (2.2 cm) formed aluminum bracket 38
28 190028 Aluminum half washer 38
32 190032 3-5/8" x 2-1/2" (9.2 x 6.4 cm) U-bolt bracket 3
33 190033 Aluminum backing plate 1
38 050038 1" (2.5 cm) black plastic cap 2
41 011941 No. 8 split lock washer 36
66 013766 6-32 x 2" (5.1 cm) stainless steel machine screw 2
84 010084 1/4"-20 (.6 cm) stainless steel lock washer 2
85 010085 1/4"-20 (.6 cm) stainless steel hex nut 2
108 351108 Male phono plug 1
112 010112 6-32 stainless steel hex nut 8
113 010113 6-32 stainless steel split lock washer 8
115 050115 Vinyl Boot 1
116 240116 Silicone Package 1
118 010118 5/16" (.79 cm) stainless steel hex nut 2
119 010119 5/16" (.79 cm) stainless steel lock washer 2
120 010120 8-32 x 2" (5.1 cm) stainless steel machine screw 14
231 010231 8-32 x 1-3/4" (4.4 cm) stainless steel machine screw 22
326 290326 Danger label 1
402 013402 5/16" (.8 cm) stainless steel flat washer 2
405 010405 4-1/2" x 2-7/16" (11.4 x 6.2 cm) stainless steel U-bolt 1
411 030411 1-1/4" (3.2 cm) stainless steel worm clamp 2
BA 1" x 43" (2.5 x 109.2 cm) aluminum tube, 12 holes 1
BB 1-1/8" x 72" (2.9 x 182.9 cm) aluminum tube, 16 holes 1
BC 1" x 71" (2.5 x 180 cm) aluminum tube, 14 holes 1
BN RG-303 coax balun assembly 2
FD 3/8" x 12-3/4" (1 x 32.4 cm) folded dipole assembly 2
PS738 Polarity switch assembly aluminum box 1
KEY P/N DESCRIPTION QTY
H2 12-1/4" (31.1 cm) aluminum rod 1
H3 12-7/16" (31.6 cm) aluminum rod 1
H4, H5 12-3/16" (31 cm) aluminum rod 2
H6, H7 12" (30.5 cm) aluminum rod 2
H8 11-7/8" (30.2 cm) aluminum rod 1
H9, H10, H11 11-5/8" (29.5 cm) aluminum rod 3
H12 11-1/2" (29.2 cm) aluminum rod 1
H13 11-7/16" (29 cm) aluminum rod 1
H14 11-5/16" (28.7 cm) aluminum rod 1
H15, H16 11-1/16" (28.1 cm) aluminum rod 2
H17 10-13/16" (27.5 cm) aluminum rod 1
H18 10-9/16" (26.4 cm) aluminum rod 1
V1 13-15/16" (35.4 cm) aluminum rod 1
V2 12-1/4" (31.1 cm) aluminum rod 1
V3 12-7/16" (31.6 cm) aluminum rod 1
V4 12-13/16" (31 cm) aluminum rod 1
V5 12-1/4" (31.1 cm) aluminum rod 1
V6, V7 12" (30.5 cm) aluminum rod 2
V8 11-7/8" (30.2 cm) aluminum rod 1
V9, V10, V11 11-5/8" (29.5 cm) aluminum rod 3
V12 11-1/2" (29.2 cm) aluminum rod 1
V13 11-7/16" (29 cm) aluminum rod 1
V14 11-5/16" (28.7 cm) aluminum rod 1
V15, V16 11-1/16" (28.1 cm) aluminum rod 2
V17 10-13/16 (27.5 cm) aluminum rod 1
V18 10-9/16" (26.4 cm) aluminum rod 1
H1 13-15/16" (35.4 cm) aluminum rod 1
2
738XB 738XB
Align these two holes
and pin temporarily.
Temporary
Pin
120
10-7/16"
(26.5 cm)
FIGURE A
9-13/16"
(24.9 cm)
BB
(16 Holes)
U-bolt holes
for mounting antenna
72"
(182.9 cm)
10-3/8"
(26.3 cm)
H10
FIGURE B
10-1/16"
(25.5 cm)
H11 H12 H14
1-3/4"
(4.4 cm)
BA
(14 Holes)
(116.8 cm)
46"
1-7/16"
(3.65 cm)
38
Use care in laying out the boom sections in order. The number of holes and undrilled spaces at the ends of the boom sections are good guides. Align the sections
and secure them with the hardware shown (Figure A). Note that the first hole in each section will line up with the first hole in the adjacent section. Temporarily
place a machine screw through the overlapping holes and secure it with a nut. Do this for each of the two joints. Measure the overall boom length 14 feet, 8
-3/4" inches (4.49 m) as a check.
2"
(5.1 cm)
6"
5-7/16"
(15.2 cm)
(13.8 cm)
H1 H13 H17 H18H16H15H2
#1 - ASSEMBLE BOOM
7-9/16"
7-13/16"
(19.2 cm)
(19.4 cm)
H3 H4 H5 H6 H7 H8 H9
5-13/16"
(14.8 cm) 3-3/4"
11
41
411
10-3/16"
8-13/16"
(25.9 cm)
(22.4 cm)
FD
2-1/4"
14' 8-3/4"
(4.49 m)
(9.5 cm)
11
41
120
Temporary
411
(5.7 cm)
Pin
KEY P/N DESC. SIZE QTY
BA ALUM TUBE 1" x 46" 1
BB ALUM TUBE 1-1/8" x 72" 1
BC ALUM TUBE 1" x 72" 1
11 010011 SS HEX 8-32 2
9-5/8"
9-1/2"
(24.1 cm)
10"
(25.4 cm)
(24.4 cm)
(12 holes) (2.5 x 116.8 cm)
(16 holes) (2.8 x 182.9 cm)
(14 holes) (2.5 x 182.9 cm)
NUT
10-3/16"
(25.9 cm)
Align these two holes
and pin temporarily.
10-9/16"
(26.8 cm)
BC
(14 Holes)
72"
(182.9 cm)
KEY P/N DESC. SIZE QTY
38 050038 PLASTIC 1" 2
41 011941 SS LOCK #8 2
WASHER
120 010120 SS MACHINE 8-32 x 2" 2
411 030411 SS WORM 1-1/4" 2
10-9/16"
(26.8 cm)
10-3/16"
(25.9 cm)
FRONT
FRONT
CAP (2.5 cm)
SCREW (5.1 cm)
CLAMP (3.2 cm)
"V"
Elements
2"
(5.1 cm)
38
38
FD
V1
5-7/16"
6"
(13.8 cm)
(15.2 cm)
2"
(5.1 cm)
7-9/16"
(19.2 cm)
411
7-13/16"
(19.4 cm)
8-13/16"
(22.4 cm)
10-3/16"
(25.9 cm)
10-7/16"
(26.5 cm)
V9 V16 V17V15V14 V18
V8V7V6V5V4V3V2
9-13/16"
(24.9 cm)
V10 V12V11 V13
10-3/8"
(26.3 cm)
9-15/16""
(25.2 cm)
3
9-7/16"
(24.4 cm)
411
9-1/2"
10"
(24.1 cm)
(25.4 cm)
10-3/16"
(25.9 cm)
10-9/16"
(26.8 cm)
10-9/16"
(26.8 cm)
10-3/16"
(25.9 cm)
4
"H"
Elements
38
View
From
Back End
738XB
Cable B
Cable A
#2 - ASSEMBLE AND ATTACH DRIVEN ELEMENTS
Slide one finished assembly (FD) over the rear of the boom and fasten it in the more forward position as shown in figure C. Attach the second FD in
the position closer to the back of the antenna and tighten hardware.
Attach the PS738 switching unit to the rear of the boom with drain holes down. Install baluns (BN) over three terminals on the each dipole. The baluns
should loop toward rear of antenna. When attaching the two feed cables leading from the PS738 be sure that they are connected to the correct dipole.
Study Figure C carefully to be sure. Tighten all hardware.
FIGURE C
Driven Element
for the "V" elements
Cable A
112
113
112
113
112
113
FD
H1
BN
112
28
113
26
66
K
C
A
B
PS738
1"
(2.5 cm)
32
84
85
KEY P/N DISPLAY DESC SIZE QTY
26 190026 MOUNTING 7/8" 2
28 190028 HALF 2
32 190032 U-BOLT 3-5/8" x 2-1/2" 2
66 013766 SS MACHINE 6-32 x 2" 2
84 010084 SS LOCK 1/4"-20 2
85 010085 SS HEX 1/4"-20 2
32
84
85
BRACKET (2.2 cm)
WASHER
BRACKET (9.2 x 6.4 cm)
SCREW (5.1 cm)
WASHER (.6 cm)
NUT (.6 cm)
66
28
H2
V1
Cable B
Driven Element
for the "H" elements
FD
KEY P/N DISPLAY DESC SIZE QTY
112 010112 SS HEX 6-32 6
113 010113 SS LOCK 6-32 6
BN BALUN 2
FD FOLDED 3/8" x 12-3/4" 2
PS738 POLARITY 1
26
BN
NUT
WASHER
ASSEMBLY
DIPOLE (1 X 324 cm)
SWITCH ASS'Y
113
112
113
113
112
112
5
738XB
#3 - MOUNT ELEMENTS
Two sets of elements are provide with the antenna. Each set is mounted
90 degrees to the other. Note that the two sets of elements are not the
same. Lengths are shown in Table A. Using Figure B for positioning,
attach the elements using the hardware shown in Figure D. Element
lengths within 1/16" (.16 cm) of the stated length are acceptable. Check
elements again to assure that they are in the correct position and tighten
the hardware. Tape feed cable A and B and baluns in place.
BOOM
231
KEY P/N DESC. SIZE QTY
11 010011 SS HEX 8-32 36
26 190026 ALUMINUM 7/8" 36
28 190028 ALUM HALF 36
41 010941 SS SPLIT #8 36
120 010120 SS MACHINE 8-32 x 2" 14
231 010231 SS MACHINE 8-32 x 1-3/4"" 22
BRACKET (2.2 cm)
WASHER
WASHER
SCREW (5.1 cm)
SCREW (4.4 cm)
120
NUT
231
BOOM
26
TABLE A (ELEMENTS)
H1 13-15/16" 1
H2 12-1/4" (31.1 cm) 1
H3 12-7/16" (31.6 cm) 1
H4, H5 12-3/16" (31 cm) 2
H6, H7 12" (30.5 cm) 2
H8 11-7/8" (30.2 cm) 1
H9, H10, H11 11-5/8" (29.5 cm) 3
H12 11-1/2" (29.2 cm) 1
H13 11-7/16" (29 cm) 1
H14 11-5/16" (28.7 cm) 1
H15, H16 11-1/16" (28.1 cm) 2
H17 10-13/16" (27.5 cm)1
H18 10-9/16" (26.4 cm) 1
FIGURE D
11
41
ELEMENT
28
120 & 231
V1 13-15/16" (35.4 cm) 1
V2 12-1/4" (31.1 cm) 1
V3 12-7/16" (31.6 cm) 1
V4 12-13/16" (31 cm) 1
V5 12-1/4" (31.1 cm) 1
V6, V7 12" (30.5 cm) 2
V8 11-7/8" (30.2 cm) 1
V9, V10, V11 11-5/8" (29.5 cm) 3
V12 11-1/2" (29.2 cm) 1
V13 11-7/16" (29 cm) 1
V14 11-5/16" (28.7 cm) 1
V15, V16 11-1/16" (28.1 cm) 2
V17 10-13/16 (27.5 cm) 1
V18 10-9/16" (26.4 cm) 1
#4 - BOOM TO MAST ASSEMBLY
It is common to mount your 738XB parallel to your 2M Yagi so that they track the satellite
simultaneously. Typically cross mounting booms are made of fiberglass, however, some
use aluminum. Attach antenna to cross boom using hardware shown in Figure E. Apply
danger label (326) to the antenna boom where it may be easily seen.
KEY P/N DISPLAY DESC SIZE QTY
32 190032 U-BOLT 3-5/8 x 2-1/2 1
33 190033 BACKING 3-1/2" 1
118 010118 SS HEX 5/16" 2
119 010119 SS LOCK 5/16" 2
326 290326 DANGER 1
402 013402 SS FLAT 5/16" 2
405 010405 SS
BRACKET (9.2 x 6.4 cm)
PLATE (8.9 cm)
NUT (.8 cm)
WASHER (.8 cm)
LABEL
WASHER (.8 cm)
5/16"x 4-1/2" x 2-7/16"
U-BOLT (.8 x 11.4 x 6.2 cm)
1
View
From
Front End
326
FIGURE E
405
32
402
33
402
119
118
119
118
6
738XB
#5 - ATTACH FEED AND POLARITY SWITCH LINES
Your Cushcraft 738XB polarity switch may be activated by applying +12V (min +9V at connector) to the center pin of the phono jack on the PS738.
When no voltage is applied the antenna exhibits left circular polarization. With +12 applied the polarization is right circular. The feedline and power
cable should be attached to the polarity switch box (PS738) and then dressed along the boom, on the side opposite where the elements
cross, toward the mast mounting plate then toward your rotor and to the shack. Be careful to leave enough cable around the
rotor so there will be slack at the points of maximum travel both horizontally and vertically. Tape both cables
securely in place.
Horizontal Mount
FIGURE F
+12 Volts DC
on Center Pin
Changes
Polarity
Coax
108
COAT WITH
SILICONE GREASE
DO NOT coat center
pin or socket!
SPECIFICATIONS
MODEL 738XB
Frequency, MHz 432-438
No. Elements 38
Forward Gain, dBdc 15.5
Front to Back Ratio, dB 25
Ellipticity dB at boresight 2
SWR 1.2:1 Typical
2:1 Bandwidth, MHz 6
Power Rating, Watts PEP 250
3dB Beamwidth, Degrees
E Plane 24
Tape
KEY P/N DISPLAY DESC SIZE QTY
115 050115 CONN 1
BOOT
116 240116 SILICONE 1
PACKAGE
108 351108 PHONO 1
PLUG
Boom Length, ft (m) 14.42 (4.39)
Longest Element, in (cm) 39.94 (35.4)
Turning Radius, ft (m) 8.5 (2.6)
Mast Size Range, in (cm) 1.5-2.0
(3.8-5.0)
Wind Load, ft2 (m2) 1.4 (.13)
Weight, lb (kg) 7.6 (3.5)
Polarity switch Included
Cushcraft Corporation, P.O. Box 4680, Manchester, New Hampshire 03108, warrants to the original consumer purchaser for one year from date of purchase that each Cushcraft antenna
is free of defects in material or workmanship. If, in the judgement of Cushcraft, any such antenna is defective, then Cushcraft Corporation will, at its option, repair or replace the antenna at
its expense within thirty days of the date the antenna is returned (at purchasers expense) to Cushcraft or one of its authorized representatives. This warranty is in lieu of all other expressed
warranties, any implied warranty is limited in duration to one year. Cushcraft Corporation shall not be liable for any incidental or consequential damages which may result from a defect. Some
states do not allow limitations on how long an implied warranty lasts or exclusions or limitations of incidental or consequential damages, so the above limitation and exclusion may not apply
to you. This warranty gives you specific legal rights, and you may also have other rights which vary from state to state. This warranty does not extend to any products which have been subject
to misuse, neglect, accident or improper installation. Any repairs or alterations outside of the Cushcraft factory will nullify this warranty.
LIMITED WARRANTY
SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE
COMMUNICATIONS ANTENNAS
P.O. Box 4680, 48 Perimeter Road, Manchester, NH 03108 U.S.A. • 603-627-7877 • FAX: 603-627-1764
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