|Dave's model was for the 2el 40m coil loaded OptiBeam and I concur with
hispost. The 40M4LLDD is a different animal, its 15m resonance was previously
posted |by
N2IC.http://lists.contesting.com/archives//html/Towertalk/2015-09/msg00315.html
John KK9A
so.... not knowing WHAT effect I’ll have with a 40M4LLDD mounted 30’ above a
6el/15 (and then another one 45’ below the first one) ... and knowing now that
the 40M4LLDD is most definitely resonant in the 15 meter band which would
generally cause pattern issues... I’m seriously thinking of rotating the 40
yagi 90 degrees to the other antennas (this is a rotating tower)...
The 40 would be mounted just above a guy point ... anyone have any knowledge of
issues that might come about due to such a change? I’m not sure what the impact
would be on wind loading ... its generally understood to rotate the elements
inline with the wind – so if I do that on the 4 monobanders I’ll still have the
elements of the 40 perpendicular to the wind (as well as the rotated 80/75
dipole at the top)... and I’ve found that wind can change enough that keeping
any particular part of the antennas inline is a crap shoot – and if one is not
at home or has lost power when a high wind situation comes up its moot as
well... but I’m curious if anyone has any mechanical expertise on such things –
if there is anything I might be overlooking or need to consider in making such
a change. I’ll model the boom of the 40 (51’) to be sure it wouldn’t then
impact the 20 or even the 15 as well... other than that I think it should work.
Since my 80/75 is rotated 90 degrees to the tower I’ll already have provisions
for a rotor direction change ... and 40 and 80 are often similar propagation so
it might work out well in that regards. I’d be thinking about having 180
degrees (south) as the rotor center point and the 40 then set at 270.... so
when the main main antennas (20/15) will go from LP AS, SA, through AFR,
MID-EAST, EU, all of Asia and most of the pacific ... from stop to stop. The 40
would start from VK/ZL through to JA and below...
Gary
K9RX
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