Force 12 Sigma-280 Magnum, Assembly Instructions Manual

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DW-Manual-Sigma-280 Magnum-001 FORCE 12 SIGMA-280Magnum Assembly Instructions Page 11 of 32
_____e) Use a good quality silicone sealant (RTV) and run a bead along the caps in
two (2) places:
_____e1. Around the hole where the element goes through each cap
_____e2. Around each cap where the cover enters the cap.
_____f) The caps and covers can be painted if desired.
IV. MOUNTING TO THE MAST
_____0) NOTE: in most installations, this antenna should be mounted parallel to the booms of
other antennas on the mast, especially 20 meter antennas, as it probably will significantly affect
them. Make a chart of the VSWR curves of the existing antennas and check them after installation of
this antenna to be sure there is no severe interaction.
_____ 1) The antenna needs to have several feet above the antenna to make room for the boom truss
attachment.
_____a) The antenna is mounted using a drop-in cradle mount that is first mounted to the
mast by several U-bolts and saddles.
_____b) Note that the cradle mount has holes drilled through it for bolts going through the
boom. The boom is not drilled until the antenna is actually installed. This makes sure the
elements are parallel to the ground and that the antenna is balanced with the coax and balun.
_____2)
Carefully lower the antenna into the cradle. Be sure to watch for the relay box control lines
and the coax feed line.
_____3)
Center the antenna for balance, align the elements so they are parallel to the ground and drill
through the boom.
_____a)
Use the holes in the cradle for a guide (the holes centered on the boom).
_____b) Drill from both sides, not only one side – it is not possible to hit the far side hole.
_____c) Slide the boom bolts through the cradle and boom. Secure with nuts.
_____4)
Open up another U-bolt and saddle, pass the truss line under the U-bolt (not under the saddle
that has sharp edges), add the saddle behind the mast and secure with the nuts and lock
washers.
_____a) Slide the truss upward to tension the truss so that the boom is almost horizontal.
_____5)
Check the antenna for resonance at the desired frequency to be sure nothing moved.
Checking now is better than later!
_____6)
Check the VSWR on other antennas in the area (i.e. on the mast) to be sure this antenna has
not de-tuned them. If the VSWR has not changed, the interaction is minimal, but the
front-to-back ratio of the other antenna(s) might have been lessened. This antenna can be
mounted parallel to the other booms for the least interaction potential. It has been
specifically designed for high reactance with other bands; however, coupling can still occur.