M2 Antenna Systems 12M4DX Manual Download Page 3

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9. HAIRPIN ASSEMBLY: Place the HAIRPIN TUBES into the clamp blocks as shown on the
DIMENSION SHEET. Rotate the tubes so the long sections are parallel. Flush the ends with the clamp
blocks and tighten the clamp blocks down enough to hold this position. Install the 1/4-20 x 1/4” set
screws into each end of the SHORTING BAR and slide the bar onto the tubes to the dimension shown
on the DIMENSION SHEET. Insert a 1/4-20 x 2” bolt from the inside of the band clamp and attach the
band clamp loosely on the boom below the shorting bar with the bolt sticking up. Slip the 3/8 x 1”
spacer tube on the bolt and then allow the bolt to come up through the center hole in the shorting bar.
Align the whole assembly, check the shorting bar position once more and tighten all hardware
including the band clamp. THIS ASSEMBLY MATCHES THE ANTENNA IMPEDANCE AND DC
GROUNDS THE DRIVEN ELEMENT FOR SOME STATIC AND LIGHTNING PROTECTION.

10. If possible, install the feedline cable at this time and route forward to center of boom. Secure with
the nylon ties supplied (ties should be snug, but not crushing cable). Seal the balun connector with
black tape, coax seal or equivalent.

11. Pick up the boom and mark the balance point. Center the BOOM TO MAST PLATE here, and
secure with two 2" U-bolts, cradles, stainless lockwashers and nuts. Two 2” U-bolts are supplied for
attaching the antenna to the mast and one more for the TURNBUCKLE PLATE.

12. 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 to turnbuckle plate.

13. Uncoil DACRON CORD. Secure one end to 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 to main line. Equalize cord length at
turnbuckle plate and cut. Put two turns through rear turnbuckle eye, pull slack out of rope, and add
three TIGHT half-hitches. Repeat for front cord section. Seal and tape cord ends.

14. Both cords should now be fairly taut and parallel with boom. Disconnect the 2” U-bolt holding the
turnbuckle plate and lift it up until the boom bows up slightly. This is approximately how high the plate
will need to be mounted on the mast when the antenna is installed. 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.

15. Check over the completed antenna and correct any minor misalignment. Also double check all
hardware to be sure everything is tight and connectors are sealed. If possible before installing set the
antenna up on a ladder or pole and run a preliminary VSWR check and a receiver check. Do all you
can at this point to determine that the antenna is working properly before placing it in its final location.

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. When stacking this antenna with
other HF models, maintain at least 8’ of separation; more if practical. Mount horizontally polarized VHF
and UHF antennas at least 40” above or below this antenna to minimize interaction.