I think this is fine solution. With 10' separation, I wouldn't expect any
significant interaction between the A3 and the D4 at any relative
orientation. But, since you will be able to rotate the D4 up to 90 degrees
relative to the A3, you can simply avoid any relative positions that are a
problem. Furthermore, since the D4 is a dipole, with 90 rotation, you can
cover all azimuths, no matter where the A3 is pointed. Finally, since the
D4 only has to rotate +/-90 degrees relative to the A3, the mechanical
issues of binding cables should be manageable. I say, "go for it!"
The things about this installation that are scary to me have nothing to do
with your original question. An A3, D4 or aluminum mast material wouldn't
survive two weeks at my location. While we don't get Katrinas, the normal
wind highs throughout the winter require much heavier duty materials on this
ridge top.
Good luck,
Ed - W0YK
> -----Original Message-----
> From: rtty-bounces@contesting.com [mailto:rtty-bounces@contesting.com]On
> Behalf Of Don Hill AA5AU
> Sent: Wednesday, November 23, 2005 5:00 PM
> To: 'RTTY'
> Subject: [RTTY] Novel idea?
>
>
> 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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