Directive Systems & Engineering DSEDPM144-5LVA User manual

DSEDPM144-5LVA Rev 10/20

Directive Systems & Engineering

2702 Rodgers Terrace

Haymarket, VA 20169-1628

www.directivesystems.com

703-754-3876

5 Element 144-148 MHz (Rear/Center Mount) Yagi,

Model DSEDPM144-5LVA

ELECTRICAL SPECIFICATIONS

Frequency range: MHz ..................... 144-148

Gain: dBd........................................... 9.0

Impedance: Ohms.............................. 50

Connector type................................... Type N(F) UG-58/U

Front -to- back ratio: dB...................... 20

SWR: Typical at resonance................ ≅1.2:1

Beamwidth: -3 degrees

E- Plane ................................. 52°

-10 dB ................................. 89.6°

H- Plane ................................. 65°

Sidelobe level: decibels

E- Plane ................................. -17

H- Plane ................................. -16

Power rating, Continuous: Watts ...... 1500

Stacking Distance: in.(m)

E- Plane.................................. 72” (1.829)

H- Plane................................. 66” (1.676)

MECHANICAL SPECIFICATIONS

Boom length: in. (m.)........................... 67”(1.7)

Turning radius: in. (m.)........................ 34”(.863)

Weight Assembled: Lbs (kg.).............. 2.8 (1.27)

Max mast size: in. (cm.).......................2”(5.08)

Wind surface area: Ft2(m.2) ............... 0.5 (.046)

Wind Survival: Mph (km/hr)................. 100 (160)

PARTS LIST

Note: All hardware is Stainless Steel unless otherwise noted.

Anti-Seize Compound –Apply a small amount of the supplied Anti-Seize Compound to the aluminum joints and

to the threads of the U-Bolts to prevent galling.

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BEFORE INSTALLING YOUR NEW ANTENNA, PLEASE BE SURE

TO READ THE ENCLOSED WARNING PAMPHLET.

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.

Tools needed: #2 Phillips screwdriver

large needle nosed pliers

keeper installation tool (supplied with kit)

ruler with metric millimeter markings

marking pencil

ASSEMBLY INSTRUCTIONS

1) The antenna components should be removed carefully from the shipping container and

the individual parts counted and checked for completeness. Be careful to check all tubing

pieces for elements and hardware that may be packed inside.

2) The element bundle contains all of the elements needed for assembly. Take time to

inventory each one and check off each dimension with Table 1. Some elements vary by a few

millimeters, so extreme care in measuring is required here. Arrange elements in order of

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DSEDPM144-5LVA Rev 10/20

descending size and mark each element with a scribe, or sharp tool to properly locate the first

keeper position. The scribe dimensions are listed in Table 1 as the “Keeper half length”. The

keepers are the stainless steel fasteners that slide over the aluminum elements. Note that the

reflector element is the longest, followed by the driven element, and then director #1. Director

#3 is the shortest element. Once you have marked each element, and using the hollow

assembly tool, push the keeper onto the element until it is just before the scribed line. See

figure 2 for proper “keeper” orientation prior to attaching the keepers. Be careful as the keeper

cannot reverse direction if you overshoot the line. You must push the keeper all the way to the

end and start over. A good trick is to install the element in a bench vise with the scribed line

flush with the edge of the vise jaws. Push the keeper until it is against the edge of the jaws.

This way, it is impossible to overshoot the scribed line. Again, be aware that the keepers are

designed to go on the element only in a certain way. Now attach one keeper to every element

as advised in Table 1 and shown below.

See pictures below for keeper orientation. The front side, with the tabs going inward, is the

side to push onto the element. The rear side, with the tabs going outward, is the side that

faces you. It is the side that goes face down into the element tool.

Keeper Front side Keeper Rear side

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DSEDPM144-5LVA Rev 10/20

3) You are now ready to install the elements on the boom. You must start at one end and

work your way, in order, to the far end of the boom. Lay out the elements in ascending or

descending order as appropriate. Install a black insulator in each side of the boom piece at

the starting end, and slide the correct element through the two insulators. Obtain a second

keeper and install that keeper on the opposite end of element #1 from the pre-installed keeper.

(See Figure 3) Check that the element is centered before you snug up both keepers. A

positioning error of +/- 2mm or 0.080" is acceptable.

4) At this point, if you tighten the keepers and the element is not centered, you will have to

cut one of the keepers to remove the element and start again. Some extra keepers are

supplied, but care is definitely required here. Check your work as you go! Proceed with the

next element in similar fashion. Check off each element on Table 1 to monitor your progress.

Double-check element lengths one last time before final installation on the boom.

5) The driven element is next. Refer to the drawing in Figure 4 and the photos in Figure 5

for guidance. The driven element slides through the boom at the ½” holes. It should slide

through with some friction and you might need to twist it back and forth to get it through. Align

the hole in the driven element with the hole in the boom. Insert an 8-32 X 1 ¾” screw through

the large hole in the bottom of the boom, through the driven element and up through the hole

in the boom. Place the T-arm support bracket on next, then the connector L bracket

(connector facing forward!). Next place a #8 split lock washer and a nut and tighten. Install

supplied 3/8” plastic plug in the driven element access hole and the 1/2” ends caps.

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DSEDPM144-5LVA Rev 10/20

FIGURE 4.

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DSEDPM144-5LVA Rev 10/20

FIGURES 5.

If you are installing multiple antennas, please be sure that you build each

antenna with the same T-match wire orientation. In the above drawing, the center pin

goes to the right hand side of the antenna as viewed from the back of the connector.

Make sure both antennas do the same! Proper phase relationship is very important

here!

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DSEDPM144-5LVA Rev 10/20

6) Next is the T-Match assembly. Once again, refer to figures 4 and 5. Starting with the left

T-arm, viewed from the rear, pass a 6-32 X ½” screw through a #6 internal tooth lock washer

and through a lug on the center conductor of the balun through a second # 6 internal tooth

lock washer, through the T-arm and into the insulator. Do not over-tighten the screw as the

threads of the insulator can be easily damaged. The right side is next. Pass a 6-32 X ½” screw

through a #6 internal tooth lock washer, then the center conductor of the balun, another #6

internal tooth lock washer, the lug from the N connector, another #6 internal tooth lock washer,

the T-arm and screw into the insulator.

7) Place a #8 split lock washer on the screw securing the driven element and the T-arm

support bracket, then the two ground lugs from the balun, then a #8 internal tooth lock washer

and nut. Tighten securely.

8) Last, pass 8-32 X 1 ¼” screws through the holes in the shorting bars and place a split

lock washer and nut on the other end. Slide the shorting bars over the ends of the driven

elements and over the T-arms and measure from the boom to the inside edge of the shorting

bars and set it at 5 ¼” inches. Install supplied 3/8” plastic caps on ends of T-arms.

9) If you requested center mount, using supplied cable ties, secure the balun to the boom

exactly as shown in Figure 6; if rear mount, secure as show in Figure 7, and route so they do

not touch any of the elements; this will ensure minimum SWR. Install supplied 1 1/8” plastic

caps on ends of boom.

FIGURE 6. FIGURE 7.

Before moving on to the following step, apply a small amount of the supplied Anti-Seize

Compound to the threads of the U-Bolts to prevent galling.

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DSEDPM144-5LVA Rev 10/20

10) Attach the boom to mast plate to the boom at the splice between the two boom screws.

Use the ¼” U-bolts with flat washers, lock washers and nuts. The antenna will be front heavy

at this point but the weight of the feedline, when attached, will cause it to be balanced. If using

multiple antennas in an array, be certain all mounting plates are at the same location. When

attaching the antenna to your mast, use the 5/16” U-Bolts, flat washers, lock washers and

nuts. Once you have the U-bolts installed and the antenna mounted on your support mast and

tightened, you can route your feedline along the mast and over to the driven element and

connector. Dress the coax against the antenna boom and tighten the connector. Seal the

connector body with several layers of good grade vinyl tape. Then apply a layer of butyl rubber

antenna sealer or RTV over the tape. This will provide a good vapor barrier and ensure years

of trouble free performance. The insulated design will make for a very long-lived antenna that

will stand up well in harsh environments.

If you wish to check your work, now is the time to apply power to the antenna. Any work

around RF energy should be done carefully. We do not recommend standing next to an

antenna with many watts of 144 Mhz energy radiating around it. Using an antenna analyzer,

VNA or low power transmitter and SWR bridge, adjust the shorting bars for minimum SWR.

Always keep the shorting bars th same distance from the ends of the driven element.

Generally, good wattmeters can reliably indicate SWR down to about 1.2:1. A high directivity

bridge or coupler can increase accuracy, but 1.2:1 is more than adequate for any installation.

The aperture of this antenna is large enough so that you must elevate the antenna a

minimum of about 10 feet or 3.0 m above the ground. Point the antenna so that there are no

"reflectors" or obstructions for 100 feet directly in front of the beam. A better method would be

to point the antenna straight up toward the sky. Support the antenna on a wooden or metal

pole or tube and tie, or guy, the antenna boom with very light string or line. Now the driven

element will be at T-arm level and ground effects are removed. Most locations are pretty clear

straight overhead as well!

Install a short length of coax (1/2 wave is ideal... The antenna impedance will repeat

each half wave from the antenna regardless of coax imperfections) between the coax

connector and your bridge or wattmeter. If you utilize your 144 MHz transmitter as an RF

source, apply power - observe the reflected power. Turn off the power and adjust the T-Match

bars equally in small increments - 1/8" or 3 mm. is a good starting point. Apply power again

and observe results. If it got better, keep going. If it degraded, change the direction of yout T-

Match movement program and recheck your SWR. At some point, you will observe a null in

reflected power. When you have found it, mark the point on the driven element and tighten the

screws on the shorting bars.

Over the years, performance can degrade due to oxidation. It is a good idea to spray

your handiwork with a good grade of clear paint sealant. As a general rule, the slower drying

sprays tend to be more enduring. Rustoleum "Clear Seal" or Krylon clear spray are

recommended. A few light coats work better than one big one.

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.

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DSEDPM144-5LVA Rev 10/20

Using the dimensions supplied, your SWR should match our plot.

This will complete the assembly of your DSEDPM144-5LVA. The construction of this

antenna will provide many years of consistent performance with no degradation of

performance due to corrosion and weathering.

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