M2 Antenna Systems 25M4, Assembly Manual

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25M4 ASSEMBLY MANUAL
8. Now adjust ELEMENT SPACING accurately following the Dimension Sheet. Dimensions given are “center to
center” or common edge to common edge. After setting spacing, align elements and tighten the 1/4-20 x 1”
bolts at the bottom of each ring clamp.
9. Now, if you haven’t already done so, attach the 3/4”, 1/2” and 3/8” element sections to the 1” tubes at the
correct location. Secure with 8-32 x 1-1/4” screws and locknuts. Repeat for all elements. MAKE SURE TIPS
LENGTHS ARE IN THE RIGHT ELEMENT POSITIONS.
10. Attach the SPECIAL 3-30 MHz, 1:1 balun (Teflon coax inside for greater power handling) to the plate at the
center of the DRIVEN ELEMENT. Secure the balun to the plate using two studs protruding from the bottom of
the balun housing. Note there are two 1/8” diameter vent / drain holes near the studs. These holes must be
DOWN. Add two 1/4-20 locknuts and tighten the balun to the plate. The balun connector should be facing
forward. Connect the terminals on the balun leads to the STUDS formed earlier in the construction. Next slide
the HAIRPIN TUBES into the 3/8 clamp block pairs, align and tighten the locknuts. Large nylon ties are
provided to secure the feed line along the boom to the mast mounting plate. Seal the feedline connector as
required with vinyl tape and coax seal or equivalent.
11. Add the 1/4-20 x 2-1/4” bolt from inside the BAND CLAMP attach the clamp loosely to the boom close to
the HAIRPIN DIMENSION on the DIMENSION SHEET. Add the 3/8” x 1” spacer to the bolt: set the 1/2 x 1/2 x
5” shorting bar on the bolt and add the 1/4-20 locknut. Align the bar with the band clamp and tighten the
locknut. Place the band clamp grounding assembly on the boom about 40 inches in front of the Driven
Element. Slide the shorting bar onto the HAIRPIN TUBES and install the two 1/4-20 x 1/4” set screws into the
ends of the shorting bar. Se the bar and clamp assembly to the dimension noted on the DIMENSION SHEET.
Align and tighten the set screws and the band clamp. NOTE: THIS ASSEMBLY DC GROUNDS THE DRIVEN
ELEMENT. THE REST OF THE ELEMENTS ARE ALREADY GROUNDED.
12. Pick up the boom and mark the balance pint. Center the BOOM TO MAST PLATE and secure with two
2-1/2” U-bolts, cradles, stainless lockwashers and nuts. Four, 2” U-bolts are supplied for attaching the antenna
to the mast.
13. To prepare the overhead guy system, begin by temporarily installing a 2” U-bolt through the TURNBUCKLE
PLATE and INTO the top set of 2” U-bolt holes on the boom to mast plate. Add a couple of 5/16” nuts to hold in
place. Unscrew turnbuckle eyes / hooks until only a thread or two shows inside the turnbuckle body and hook
them into the turnbuckle plate.
14. Uncoil the 5/16” DACRON CORD. Secure one end to the rear eyebolt, taking two turns through the eyebolt,
then adding three TIGHT half-hitches. Pull hard on cord to set the knots. Repeat for the front eyebolt. Seal cord
ends with heat (lighter, propane torch, etc) and tape the main length.
15. Equalize cord length at turnbuckle plate and cut. Put two turns through the rear turnbuckle eye, pull slack
out of rope, and add three TIGHT half-hitches. Repeat for front cord section. Seal and tape cord ends.
16. Disconnect the 2” U-bolts holding the turnbuckle plate and lift it up until the boom bows up slightly. This is
approximately how high the plate will be when the antenna is installed on the mast.
17. During final installation on the tower / mast, secure the turnbuckle plate at the appropriate height with the 2”
U-Bolt. Then lean or pull on the cords to increase the tension and help the knots take their final “set”. Make
sure the knots are not slipping. When the guy system has taken a “set”, loosen the 2” U-bolt and adjust
turnbuckle plate height until boom is straight and level. Finer adjustments can be made at any time, if
necessary, with the turnbuckles.
18. This completes the ASSEMBLY, REMEMBER to support the feedline at the antenna boom and on the
mast. Leave an adequate feedline loop for rotation around the tower. Mount any horizontally polarized VHF and
UHF antenna AT LEAST 40” above or below this antenna to minimize interaction.