[TowerTalk] Telephone pole yagi mount?

[Scott Robbins]

>
>Hi all!!
>
>Could I have you opinions as to using a telephone pole for a tower.
>
>The height or the pole is 50', with another 10 ' in the ground and, it
>is approximately 3 to 4 feet wide at the bottom.  It will be supporting
>a rotor, 22 element 70 cm beam, 15 element 2m beam, and a 2m 70 cm
>vertical.
>
>Does anyone have any idea if this is feasible and if so does more of the
>pole need to be in the ground.
>
>Thank you
>
>Bryan Fields, KB9MCI
>

>
Hi Bryan:

I have a 40 foot high telephone pole in my side yard that was 
installed specifically for supporting amateur radio antennas back 
in 1968.  (I'll confuse the issue by saying I didn't move into this 
house until 1997, the owner of the house installed the pole in 1968.  
Leasing a house from a fellow ham certainly makes explaining why
you need all those antennas in the yard a piece 'o cake...)

You've got a couple of options for rotator mounting.  The original
installation was a HAM-M rotor mounted on the very top of the
telephone pole, encased inside a partially opened wooden box that
was in turn bolted on four sides to the pole, turning a TH6DXX
yagi.  This rotator was installed in 1968, and is now mechanically
dead but still mounted at the top of the pole.  I think it's safe
to say this rotor mount has worked for the long haul, having been
there 31 years now...

I mounted a Cushcraft A3S with a Yaesu G800S rotor up on the pole
in the fall of 1997.  The mount for the rotator is a utility company
transformer pole mount with a steel rotator plate welded to the
transformer mounting bracket, with holes drilled to fit the rotator
bolts sticking off the bottom of the Yaesu rotator.  The bracket 
itself is bolted to the pole with 4" long 3/4" diameter lag bolts
as per manufacturers instructions.  The rated vertical weight
capacity of the mount is 4000 pounds (so it ain't going anywhere).
It's mounted about 5 feet below the top of the pole.  I used a
standard 2 inch OD pipe 8 feet long as the mast and bolted the
A3S on.  Works fine, except for overhanging trees nearby that 
interfere with the rotation of the antenna.  Credit where it is
due: K1KY came up with this idea for mounting. 

Also on the same pole, I have a second yagi (Hy-Gain TH3) side
mounted to the pole, fixed west, at 28 feet high.  The sidemount
for the pole is two L shaped pieces of metal, each approximately 
6 inches x 6 inches with a L bend about two inches in from one

side.  Two holes in each "short" side of the "L".  Bolted to the
pole with the same type lag bolts as used on the above transformer
mount.  The two L brackets are spaced about two feet apart on the
pole.  Each has holes drilled for, and accepts, two U-bolts each
(total of four).  The remaining 2 feet of 2" OD pipe (cut off
from the original 10 ft. section I used to fabricate the 8 ft.
mast for the A3S) is U-bolted between the brackets.  The boom of
the TH3 is then attached to the 2 feet of pipe.  Works great!
You can easily see how a side-arm could be fabricated to mount
a rotator below the top of the pole and make this a rotatable
antenna as well.  These antennas are phased together with a WX0B
matching box and work fantastic for mult hunting in DX contests
or for high angle spray CQing for domestics when the big antennas
are pointed somewhere else.

I live in a high wind area.  If you look at the Rohn wind charts
for Tennessee it's where bells start ringing.  I've had elements
spiral and even be blown off these antennas and the mounting
arrangement on both doesn't flinch.  Had a friend just go up there
to re-attach 1/2 of the driven element on the A3S that I found 
speared into the ground after we had a 50-60 MPH roaring wind
storm through here three weeks ago. 

73,
Scott Robbins, W4PA 

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Visit the Tennessee Contest Group at <http://www.k4ro.net/tcg.html>
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The views expressed above do not represent the view of my employer.


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