Directive Systems & Engineering DSE3-50 User manual

DSE3-50 Rev 6/20
Directive Systems & Engineering
2702 Rodgers Terrace
Haymarket, VA 20169-1628
www.directivesystems.com
703-754-3876
3-ELEMENT 50-MHZ YAGI, DSE3-50
INTRODUCTION
The Directive Systems DSE3-50 is a 3 element Yagi-Uda antenna that provides optimum
performance for a 6-foot boom-length antenna, while addressing construction details of importance to
the first-time, as well as the experienced, builder. Design issues such as selecting the grade of
aluminum used for boom and element material to assure harsh-environment survivability, use of
stainless-steel boom hardware and element-assembly hardware, and use of commonly available
hand tools to aid in ease of construction, have been considered in producing an antenna kit which is
complete, satisfying to build, and gives the builder one of the finest 6-meter antennas available.
ELECTRICAL SPECIFICATIONS
Calculated gain: 8 dBi
SWR 1.5:1 Bandwidth: 2 MHz
SWR 50.1 MHz Less than1.3:1 typical
F/B ratio: >20 dB
Impedance: 50 ohms nominal
Maximum Power: 1000 Watts
MECHANICAL SPECIFICATIONS
Length: 6 feet
Turning radius: ~96 inches
Boom-sections/elements 6063-T832 aluminum
1.375" x .058" wall
Element sections: 5/8" & ½" x .058" wall
T-match arms: 3/8" x .058" wall
All stainless steel hardware.
Surface area: ~1.5 square feet
Wind survival: 90+ mph
Maximum mast size: 2.0" OD –larger on Special orders
Coax connector: Weatherproof N–type
Assembled weight: 7.5 lbs
CAUTION: While we strive to remove all burrs from all machined parts, there is always the possibility of
sharp edges. We strongly suggest checking the edges and use a fine file, or 400 grit
sandpaper, to remove any burrs that may have been left.

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BEFORE INSTALLING YOUR NEW ANTENNA, PLEASE BE SURE
TO READ THE ENCLOSED WARNING PAMPHLET.
ASSEMBLY TIPS AND NOTES
TOOLS
Assembly of your antenna kit requires the following tools.
12’ or greater tape measure
#2 Phillips screwdrivers
7/16” wrench or rachet and socket
Permanent marker (Sharpie)
Pliers
ASSEMBLY TIPS
1. Read an entire section before performing each assembly operation.
2. This Manual contains assembly drawings and other assembly-related information such as
element lengths. Drawings are referred to by Figure number; charts and lists are referred to
by Table number. Continue using the same Table or Figure number until told to use a different
one.
3. All of the information needed to successfully complete the construction of an antenna kit is
contained in this Manual. Keep this Manual in a safe place so that it will be available should
you require it for future reference.
4. When tightening hardware FOLLOW INSTRUCTIONS –DO NOT OVER TIGHTEN!
Deformation of the boom may occur, causing misalignment of elements.
5. Orient all hardware as instructed in each assembly step and as may be shown in an
associated figure.
Elements will be called out by their position on the boom, R = reflector, DE = driven element and D-
element number = director. The director’s number is relative to the DE element with D-1 nearest the
DE. The elements are marked R, DE and D.

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PARTS LIST
Note: All hardware is Stainless Steel unless otherwise noted.
Unpack the antenna kit and check each part against the following list. Do not throw any packing
material away until the antenna is completely assembled and ready for final installation. Some parts
may be packed inside boom sections.
The box in which the antenna was shipped contains the following items:
1 6’ boom section
1 Boom to mast plate
6 Element halves (R, DE, D)
3 Element couplers
2 48” T-arms
1 Connector bracket assembly
1 Balun
1 Anti Seize Compound
Hardware Bag
Boom-to-Mast Hardware
2 T-arm shorting bars
4 8-32 x 1¼” Machine screws
5 #8 Nuts
4 #8 Split lock washers
2 #8 Internal tooth lock washers
2 6-32 x ½” Machine screws
5 #6 Internal tooth lock washers
3 1 ½” U-bolts
6 ¼” Locknuts
2 ¼” x 1 ¾” U-bolts
4 ¼” Nuts
4 ¼” Lock washers
4 ¼” Flat washers
2 5/16” U-bolts
4 5/16” Nuts
4 5/16” Lock washers
4 5/16” Flat washers
3 Element saddles
6 ½” Element End caps
2 3/8” T-arm End caps
2 1 3/8” End caps
3 Cable ties
Anti-Seize Compound - Apply a small amount to the aluminum joints to prevent the aluminum from
oxidizing and to the threads of the U-Bolts to prevent galling.
ANTENNA ASSEMBLY
1. Locate the 6’ boom section and, using a permanent marker (refer to Figure 1), place a mark 2 ¼”
from one end of the boom –this is the Reflector point. All further measurements are made from
this end of the boom. Next, place a mark at 42 ¼” – this is the Driven Element point. Next, place a
mark at 34 ¼” – this is the center line of the boom-to-mast plate. Last, place a mark at 69 ¾” – this
is the Director.
If this DSE3-50 has the rear mount option, place a mark 3 7/8” from the end of the main boom.
Slide the 12” piece of 1 ½” tubing to this line, with the slits over the boom.

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DSE3-50 Rev 6/20
Mount the reflector 11 ½” from the rear of the boom extension. Tighten this U-bolt securely as this
connection keeps the antenna horizontal. If your location is subject to icing, we recommend
installing a sheet metal screw to lock these two boom sections together.
2. Starting with the Reflector elements (R), slide the two halves into the element coupler until you
see the holes in the elements line up with the holes in the element coupler. Pass a U-bolt from the
hardware bag over the boom, through an element saddle and then through the holes in the
element. Align this assembly on the rear of the boom so that the U-bolt covers the mark you made
in step #1. Install two ¼” locknuts and tighten.
2 ¼”
34 ¼”
42 ¼”
69 ¾”
D
105" DE
112¾” R
117"
DSE3-50 Dimensions
All distances measured
from rear of boom
Drawing not to scale –all
dimensions +/- ¼”
Boom to mast bracket
Figure 1
3. Similarly, assemble the Director (D) and attach it at the appropriate mark on the boom, making
sure the element is perpendicular to the Reflector.
4. The Driven Element (DE) mounts the same way; however, the connector bracket sits between the
element and the element to boom saddle (see Figure 2).
5. Locate the two 48” x 3/8” T-arms and the balun, and from bag #3 locate the T-arm shorting bars,
the #8 hardware and the #6 hardware. The connector bracket came with the Delrin standoffs
already installed. Using a 6-32 X ½” screw, place an internal tooth lock washer on the screw and

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DSE3-50 Rev 6/20
put the screw through one of the balun lugs connected to the center conductor. Next, place a
second internal tooth lock washer on the screw, then insert the screw through the lug from the
coax connector. Last, place a third internal tooth lock washer on the screw, then insert through
one of the tee arms and screw it in to the Delrin standoff insulator. Do not over tighten the screw
as you can strip the threads in the standoff insulator.
6. Slide the T-arm shorting bar over the end of the driven element and the T-arm. The shorting bar
should be about 13” from the outer end of the driven element. Install 8-32 X 1 1/4” screws through
the two holes in the shorting bars and install a lock washer and nut. Tighten both the shorting bar
screws. Attach the other T-arm in a similar fashion, but without the wire coming from the
connector and locate the shorting bar about 13” from the end of the other driven element half.
Boom
1/4" X 1 1/2" X 3" U-BOLT
Delrin standoff insulators
connection point for
Balun and T-match arms
Front
Driven element
Element Saddle bracket
N-Connector
¼” Locknut
Figure 2
7. Connect both ground wires from both ends of the balun to the grounding screw just below the
connector. Place a lock washer on the stud first, then both lugs, another lock washer and then the
nut and tighten. Refer to Figure 3 for details.
8. Dress the balun along the boom or coil it as pictured. Securely tape the balun to the boom or use
cable ties as pictured.
Figure 3

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9. Install supplied plastic caps on ends of tubing.
10.Place the boom-to-mast plate against the boom at the marked center line (Step 1) and from the
Boom-to-Mast hardware bag, use two ¼” U-bolts, ¼” flat washers, lock washers and nuts. Tighten
the four ¼” nuts, making sure the boom-to-mast plate is perpendicular to the elements.
11.This completes the antenna assembly. Using the dimensions shown, the SWR below 50.4 MHz
will be 1.3:1 or less. If you wish to improve the match, support the antenna at least one
wavelength above the ground (about 20 feet). Check the match using a directional wattmeter or
antenna analyzer. You can move the shorting bars in or out to change the match on the antenna.
Always use coax in multiples of one half wavelength when testing to ensure you are seeing the
real match of the antenna. After completing your match adjustment, or if you don’t want to adjust,
tighten the four nuts on the shorting bars.
DO NOT, UNDER ANY CIRCUMSTANCES, APPLY ANY TYPE OF SEALANT OR COATING TO THE
DRIVEN ELEMENT, T-ARMS OR CONNECTOR ASSEMBLY, OTHER THAN KRYLON®
CLEAR COAT. ANY OTHER COATING WILL ADVERSELY AFFECT THE SWR AND VOID YOUR
WARRANTY.
Directive SystemsWarranty Policy
All Directive Systems antennas are built with the finest materials available. We take great pride in
building a quality product that will give years of good service and performance. If there is a defect in materials
or workmanship within 90 days of purchase, Directive Systems will repair or replace the defective part, free of
charge, to the original purchaser. DO NOT RETURN ANYTHING WITHOUT PRIOR AUTHORIZATION FROM
DIRECTIVE SYSTEMS. Please contact us either by phone or email describing the problem and we will resolve
your problem.
If, after examining a new antenna you received, you are not satisfied, contact us immediately for return
authorization and refund. ANY ANTENNA THAT HAS BEEN MODIFIED WILL BE SUBJECT TO A
RESTOCKING CHARGE. IF AN ANTENNA IS SO MODIFIED AS TO MAKE IT UNUSABLE, DIRECTIVE
SYSTEMS RESERVES THE RIGHT TO REFUSE TO ACCEPT THE ANTENNA FOR RETURN.