M2 Antenna Systems 20M4DX Assembly Manual page 3

20M4DX ASSEMBLY MANUAL
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. Refer to the figure "DRIVEN ELEMENT ASSEMBLY." Attach the 3-30 MHz 1:1 BALUN to the
plate at the center of the DRIVEN ELEMENT. Secure with a 2-1/2" U-bolt and cradle but do not over
tighten. The balun connector should be facing forward and be positioned so the connector face is just
ahead of the Poly Disk insulator under it. Remove the two 1/4-20 locknuts from the two studs, slide on
a pair of clamp blocks to both. Now connect the balun leads on top of the clamp blocks and rethread
the 1/4-20 locknuts onto the studs. A short section of main feed line can be added at this time. 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 a 1/4-20 x 2" bolt to the BAND CLAMP and form another STUD by locking the bolt in place
with a plain 1/4-20 nut. Place the band clamp loosely around the boom about 22 inches in front of the
DRIVEN ELEMENT place the 1/2 x 1/2" x 5" hairpin SHORTING BAR on the stud and add a locknut
loosely. Install the 1/4-20 x 1/4" set screws in the SHORTING BAR. Now insert the HAIRPIN TUBES
into the clamp blocks and slide the shorting bar assembly over the tubes. Align the tubes and tighten
the 1/4-20 locknuts securely. Tighten the SHORTING BAR to the BAND CLAMP. Adjust the shorting
bar to 22" between it and the 7/8" rod insulator. Tighten the SHORTING BAR SET SCREWS. Now
tighten the band clamp to the boom. NOTE: THIS ASSEMBLY DC GROUNDS THE DRIVEN
ELEMENT. THE REST OF THE ELEMENTS ARE ALREADY GROUNDED.
12. Pick up the boom and determine the balance point. Mark this location and center the BOOM TO
MAST PLATE here. Secure the plate 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 DACRON CORD. Secure one end to rear eyebolt, taking two turns through the eyebolt, and
securing with 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 length.
15. Equalize cord length at turnbuckle plate and cut. Put two turns through the rear turnbuckle eye,
pull slack out of rope. Secure with three TIGHT half-hitches. Repeat for front cord section. Seal and
tape cord ends.
16. 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 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 antennas AT LEAST 40" above or below this antenna to minimize interaction.