N5KD Roof Tower Mounting Information.


This was my Force12 C3D beam when erected 8th May 2000.

You will notice a strange vertical object on top of the tower, but below the antenna.  This is an ALS-100 made by Lightning Prevention Systems Inc.
It is very well bonded to my ground system. It is supposed to prevent lightning strikes. We will see if this is true in the long term.
The single most frightening aspect of using a roof tower is the possibility of a lightning strike. Whenever thunderstorms are in the area I have a sleepless night.

Only time will tell if the ALS-100 actually works.  However, if that is what is required to get XYL permission for any beam, then so be it.

I have not done any study to see if the ALS-100 creates any extra QRN in the process. Comments???




Same image in October 2017.

New house next door & massive tree growth.
Just had the tree trimmed by "Klime Time" Tree Service in Dallas.
I was fed up with bent and broken elements. (Mostly the 20m reflector).






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Here is a view of the Roof Tower. The tower is a CREATE CR18, made in Japan. Its a 1.8 meter tall aluminium tower. As you can see the roof is fairly steep and mounting the tower was a challenge.
Rotator is an M2 (Orion) RC-2800P
Beam is a Force12 C3D.

The Comet Antenna website still shows this roof tower
in it's price list. I bought mine used.



The roof tower sits on top of two wooden planks. They are to spread the weight over a couple of the rafters inside the roof. It is so the spot weight at the bottom of the legs is not sitting at one point. The tower is bolted to the mounting plates by stainless steel nuts (self locking) and two lengths of 1/4 inch all-thread per leg.



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These two pictures show how the tower is mounted inside the roof. On each side of the roof a 2 by 6 inch piece of timber about 6 foot long is fitted onto the 1/4 inch all-thread coming through holes drilled through the roof. As each leg of the tower has two pieces of all-thread, you can clearly see how both legs are mounted in the picture on the left.

In addition a piece of 2 by 4 inch timber is placed on edge between the two pieces of all-thread. This means all the wood together forms an I-Beam structure, clamped together by the two all-thread supports on each tower leg.

Additionally, the longer beams on the outside and inside of the roof spread the wind loading over several joists.



For 80, 40m & 30m I use a Hy-Gain Patriot AV680 Vertical. It works very well.