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Re: "Pipe tower" mounting for G5500 stack...



Most "brick houses" merely have a brick façade.  The brick is not
structural, and is not a good antenna support.  I have had success with
"pipe" mounting of various antennas.  I did that once for a small R5 HF
vertical.  It survived big storms, but the pipe only extended 5 feet above
the top anchor point, and an R5 vertical has much less mass and wind load
than a typical satellite antenna/rotor array (especially with a dish!).

I note that you are trying to get the antennas 17 feet above the brick wall.
You need a "real" tower to go that high without guy wires.  It's easy and
cheap to get the antennas 12 feet above the roof with guy wires.  I did this
for a small HF yagi.  Get a 5 foot roof tripod ($25) from AES.  It has 3
bolts at each of the mast anchor points which do a good job of keeping wind
torque from twisting the mast.  Get a 10 foot piece of 1.25 inch EMT conduit
($5) from your local hardware store.  You will need one tier of guy wires
attached just below the rotors.  The guy anchors and tripod feet should be
screwed into rafters, not just into the roof cladding.  I used the beefiest
anchor ring bolts and turnbuckles that I could find at my local hardware
store, and I used two cable clamps at each end of the guy wires. You need a
lot of tension on the guy wires to minimize oscillations in high winds.
Such a setup is quite easy to take down for maintenance, even without a
helper.  On a day when the wind is light, unscrew two of the guy wire
turnbuckles and remove the bolt from the tripod leg that has a removable
bolt (the other two legs have hinges).  Then hinge the assembly down to the
roof, "walking" your hands along the mast to the antennas.

Since 1995 my satellite antennas have been on an UNGUYED 5-foot roof tripod
with 6 feet of 1.25-inch EMT conduit (1.5 inch O.D.) as the mast.  The
azimuth rotor is 8 feet above the roofline - I wouldn't go any higher
without using guy wires.  Each tripod leg has at least one lag bolt screwed
into a rafter.  This setup survived 50+ mph winds several times, but that
was before I added the BBQ dish.  On top of the mast are Orbit-360 rotors
(small and light), 8-foot crossboom, 10-foot 2m CP yagi, 9-foot 70cm CP
yagi, and a 2x3 foot wire dish.  I don't think I've had winds over 40 mph
since adding the dish, so I don't know if the addition of the dish will
cause the array to collapse in a 60 mph wind.  Lots of tall trees shelter my
house from prevailing winds, so I'm confident that the wind won't exceed 60
mph even though I live in an 87 mph zone.  Unfortunately, those sheltering
trees obstruct S-band reception below 12 degrees to the west.

In summary, I think "pipe" antenna supports are practical if you:
1. Anchor the base with a 5-foot roof tripod.  The tripod provides a wide,
stable hinge for raising/lowering the array.
2. Use reasonably short pipe (perhaps 15 feet max with 2 tiers of guy
wires).
3. Use guy wires if the pipe extends more than 5 feet above the highest
anchor point.
4. Have reasonably small wind loading (forget about a solid 1.2m dish!).

Using a roof tripod as the anchor and hinge, I estimate that a 15-foot pipe
is the longest that could be used.  You are limited to 2-inch diameter pipe
to fit into the tripod and the azimuth rotor.  A 2-inch pipe longer than 15
feet probably isn't rugged enough to handle "hinging" a heavy antenna/rotor
array up and down (there would be 12.5 feet of pipe between the top of the
tripod and the bottom of the azimuth rotor clamp).  A 15 foot pipe mounted
in a 5-foot roof tripod would put the azimuth rotor about 17 feet above the
roof.  Such a setup would need 2 tiers of guy wires to keep it from
oscillating in high winds.  And you would probably need a helper to put it
up and take it down.

Wayne Estes W9AE
Mundelein, IL, USA

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