[VHFcontesting] Chimney and/or tower mounts
ve3cru at rac.ca
Sat Dec 2 13:46:28 EST 2006
My house is 33 years old. The chimney serving the fireplace at the east side is clay brick construction. It for years held only a deep fringe tv antenna on an AR-40 rotator. That system was removed 10 years ago or more.
Since getting my ham license 4 years ago, I have anchored a 30' tv tower to the chimney. It extends 8' above the roofline, and 7' above the point of anchor. Six feet above chimney too. The anchor consists of two pieces of 4 by 4. One piece is notched to fit the legs of the tower, and both pieces are drilled for 3/4" continuous thread running through them, snug to the chimney so no side movement is possible either.
Any stresses are usually wire antennas which load towards the house, as the tower is 8 feet from the property line. The only beam ever on top was a 5 element 2 meter at one time. At the west corner of the house is another 30' tower, guyed, with a 6 meter antenna up 36' and a tribander below it. As you can see, the anchor point of the east tower is 23 feet from the ground. I would never put up anything that was anchored lower to a chimney due to the stresses and risk, such as using 40' or more of tower to it. Cinder block.....well, not sure of it's strength. Don't think any chimneys are anchored to the house, but are free standing on their base, usually part of the foundation.
I would not load any chimney as heavily as what you are planning, regardless of bracket strength available.
My two cents, anyways.
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