Hi Jon,
There is a lot of expertise in this group but if you wouldn't mind looking
over my plans and letting me know if I'm FUBAR or OK, I'd sure appreciate
it.
My plan is to the following: I have an existing GM RT-832 roof tower with a
G800DXA rotator and Yaesu GS-065 thrust bearing. It's currently holding a 5
el 6 m and 70 cm yagi on a 10 ft length of 2" aluminum conduit. The roof
joists are doubled or tripled where the mounting feet are located. I just
replaced my roof and don't want to trash it by doing anything stupid like
overloading this light duty roof tower and taking my $20K roof out.
I bought a 2 inch 12 ft 15 lb 6061 mast and want to install a Hy-Gain 2 el
trap TB, 20 lbs, 3 sf, 14' radius, an M2 6m 5 el yagi, 2.2sf 13 lbs, 11 ft
radius, and, if possible my 2 meter M2 9 el, 1.2 sf, 6 lbs 8 ft radius on
top (very optional). The 70 cm is coming down and will be sold.
The K factor in the Yaesu manual is for this rotator is 180. If I only put
the 2 el HF yagi and 6 meter on the mast the calculated K factor is 231, 51
higher than recommended by Yaesu. If I add the 2m then I'm over by 77. The
Yaesu manual equation doesn't count wind resistance, just antenna and mast
weight and turning radius. The thrust bearing takes most of the weight of
the mast and antennas but there's nothing in the manual to account for that.
I'm OK on weight for the GM roof tower but the manual calls for no longer
than a 9 ft mast, and the rotator plate is 6 ft from the top, not much room
for antennas! I think I'll be OK with 12 ft even if I add the little 2
meter yagi at the top, but the tribander and 6 meter both have to go on the
mast and the 6 meter won't be anywhere near the top since it's a big
antenna.
I got a 12 ft mast because that's what my friend had in his garage - if he
had 9 ft or 11 ft it wouldn't make much difference to me since I won't have
enough room for optimal spacing in any case..
In your collective experience, am I cutting things too close for comfort?
I have a TA-33 but I think it's too much antenna for this roof tower and
rotator with a K of 262 which is why I'm going with the 2 el Hy-Gain,
lightweight with low wind resistance.
Most of this project except for the roof tower and meter M2 yagi are used
items from from fellow hams who are trustworthy.
Thanks for your assistance.
73,
Dave WB2PJH
FRC, CWOPS
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