Date: Wed, 23 Nov 2005 20:09:33 -0500
From: t3 <t3@semarg.ath.cx>
I can't see a problem..
except, maby the rotor cable on the upper rotor may get large doses of
RF while it passes between the A3S
a simple fix could be sheilded cable..
Tony
NN1D
Another fix for this would be to run the control cable fro the rotator
up through the mast, come out the top and then down to the rotator.
I like the idea, and it cries out for a couple of computer controlled
rotators and a microprocessor to be the glue to actually calculate and
display the radiating directions for the top antenna. I'm not
volunteering, though.
73, doug
Don Hill AA5AU wrote:
> This is not directly related to RTTY, but again, I trust the opinions of
those
> on this reflector. A great bunch of ops here.
>
> I've not ever heard of anyone doing this before. But it seems to be an
> excellent solution for me. I was going to keep this secret, but I just
can't.
> I need some input from others.
>
> I'm in the middle of rebuilding my main tower. Right now, it's at 46 feet
> waiting for me to install the first set of guys. Why the unusual height?
Six
> feet of tower sticks out from the concrete base. What I have left is one
more
> 10' midsection, then the 9' top section. The tower will be at 65' when
> finished.
>
> Anyway, for those following my rebuild may remember that I wanted to
install a
> 40 meter beam. Well, I cheaped out on this idea. In order to get
something up
> for Roundup, I've purchased a new A3S and D40 (D40 is a Cushcraft 40M
dipole).
> You have to realize that my ground crew consists of my wife and the
neighbor's
> German Shepard. So I have to stay lightweight right now.
>
> Prior to Katrina, my main antenna was an A3S with the 40 meter add-on.
With the
> D40, the rotatable dipole will now be separate from the tribander and I
can use
> both antennas at the same time with my SO2R setup.
>
> Here's the kicker. I will install the D40 above the A3S and want at least
10'
> of separation. In trying determine if I should align the D40 with the A3S
or
> offset it 90 degrees in azimuth, I have come up with a radical idea of
> installing a separate rotor above the A3S. My main rotor is the M2
RC2800. It
> will sit inside the top section. I will then install a piece of 2"
aluminum
> conduit (mast) from the rotator up through my thrust bearing, but only
sticking
> out of the tower a couple of feet. I will install the A3S here. On top
of the
> conduit mast sticking a couple feet from the top of the tower, I'll
install what
> will probably be a Yaesu G-450A with the mast mount (haven't purchased
yet) and
> then a 10' piece of 2" aluminum conduit. Near the top of the 10' piece of
> conduit, I'll install the 18 lb D40. I've compiled the figures and the M2
is
> more than enough to rotate everything and the G-450A will handle the D40
with no
> problem. What I like about the G-450A is that it can be set to stop at any
> direction and shows an LED for overlap which I can set at 90 degrees.
Also,
> unlike the G-800S, you must push the left or right button to move it, so it
> won't rotate all the way around by itself. This is important because of
the
> slack I'll need in the RF and rotor control cables from the D40 and
G-450A. The
> overlap LED will alert me that the D40 is offset. Keep in mind that the
D40
> will only need to be rotated up to 90 degrees offset from the A3S, never
any
> more than that.
>
> I've been thinking about this for weeks. I can't think for any reason why
it
> wouldn't work. I hope to simulate the entire setup on the ground,
possibly this
> weekend using an old CDE mast mounted rotator I have. Other than the
G-450A, I
> have all the other hardware already. Has anyone ever heard of this setup
> before, a rotor on top of a rotor?
>
> By the way, updates on the towers on my new antenna page at
> http://www.aa5au.com/antennas/antennas.html
>
> 73, Don AA5AU
>
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>
>
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