A. Install the 5/16” EYEBOLTS to the outer ends of the boom, securing with stainless 5/16” nuts and
lock washers. Align the eyes parallel with the boom and tighten.
12. For ease of element installation, support the boom about 2-3 feet above ground. Loosely attach
the BOTTOM CRADLES to the bottoms of the clamp plates using the 1/4-20 x 2-3/4" bolts. (BE SURE
TO USE ZINC PASTE ON THESE THREADS). Slide the REFLECTOR clamp plate onto the boom
end. Level the reflector element and tighten all four bolts EVENLY and firmly. Repeat for the DRIVEN
ELEMENT on the other end of the boom. ADJUST EITHER ELEMENT TO THE PROPER SPACING
BETWEEN ELEMENTS. Make sure the saddles are straight and level. A cocked clamp will loosen
quickly in the first wind. Align the elements and tighten the hardware
13. Now take a step back for a moment to observe any misalignment (if any) and the “droop” in each
element. Simply look down either the front or back of the boom to do this. If you have not already
done so, adjust each turnbuckle until each element droops 6 to 10 inches at the tip. NOTE: The
elements are the most stable in wind with a small amount of tip droop. ADJUST FOR LEVEL INNER
SECTIONS AND THE CORRECT TIP DROOP WILL BE AUTOMATIC. After the adjustments have
been made, proceed with tightening the 1/4-20 JAMNUT on all the turnbuckles.
14. 1:1 HF BALUN INSTALLATION — SEE ASSEMBLY DRAWINGS AND DIMENSION SHEET
Mount the balun to the angle plate on the driven element using a 2-1/2” U-bolt and saddle. Be sure the
balun vent hole is down. Do not over tighten as balun damage may occur.
15. INSTALLING THE HAIRPIN (MATCHING ASSEMBLY)
A. Apply a little Penetrox to the balun terminal lugs. Remove the nuts holding the 3/8 clamp blocks
and place the balun lead lugs over the studs. Replace the nuts loosely. Apply a little Penetrox to
the shorter bent ends of the hairpin tubes. INSERT the tubes into the grooved channels of 3/8”
clamp block assemblies on
Driven
element.
Push the tubes through until at least 1/4" extends
beyond clamp and then tighten the clamp bolt slightly to hold the tubes from slipping. Rotate the
tubes so the bends are level and the long sections are parallel to the boom.
B. Install the 1/4-20 x 1/4” set screws into the ends of the HAIRPIN SHORTING BAR. Insert a 1/4-20
x 2” bolt into the hole of the #52 stainless band clamp from the inside and add the 3/8” x 1”
aluminum spacer. Add the shorting bar and the lock nut loosely to hold the assembly together.
Open the clamp and set it over the boom about 60 inches from the driven element. Now slide the
assembly to the ends of the hairpin tubes and insert the end into the shorting bar. ( lubricant like
WD-40 or zinc paste will let the shorting bar slide easier on the tubes. Position the shorting bar 38
inches from the driven element. Align the assembly, and tighten the band clamp. Next tighten the
nut securing the shorting bar and finally tighten the set screws onto the tube. NOTE: IF YOU CAN
DO FINAL VSWR MEASURMENTS AND ADJUSTMENTS DURING THE FINAL INSTALLATION,
DO NOT TIGHTEN THE SET SCREWS YET. SEE THE NOTE AT THE BOTTOM OF THE
“DIMENSION SHEET”
C. Now return the to balun end of the hairpin assembly and final tighten the bolts holding the tube
ends and the balun leads.
16 Attach the BOOM TO MAST PLATE at the balance point, using the two large 3” U-bolts, 3/8-16
stainless lockwashers, and nuts. Align plate to vertical and tighten nuts.
17. OVERHEAD BOOM SUPPORT SYSTEM.
A. Attach one end of the 5/16" Dacron cord to the rear eyebolt using two turns around the eyebolt and
a series of three half hitches or equivalent knots. Finish with about 6 inches of cord after the knots.
Without cutting the cord, do the same at the front eyebolt.
Pull on the knots
HARD
to
SET
them.
Seal ends with heat or flame to prevent fraying. Tape the excess 6 inches of cord back to main cord
tightly with black vinyl electricians tape.
40M3L ASSEMBLY MANUAL
