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<jbrannig@optonline.net> writes >Your experience with F-12 seems to be the exception and might fall under the >category of "Stuff happens". Maybe, but when "stuff happens", it's how the manufacturer deals with it that distinguishes a good company from a not so good one. >It would be useful to see the antennas that >did survive your particular conditions. >We would all learn from it. I'd be happy to describe what we done to ensure survivability. We didn't really do anything special apart from using good engineering practices. We built the antennas to what we believed would survive after seeing how other commercial antennas belonging to other hams have failed. For the elements, we don't use paper thin aluminium. All elements use a 3mm wall (~1/8") throughout, apart from the short 1/2" tips which are about 1.5mm (~1/16"). No part of any element is less than 1/2" diameter, even on 6M. The booms are mainly 2" diameter (the 40ft 20M one has double, three-way bracing) and we always use a 6mm wall (~1/4"). As for mounting the elements to the booms, that is done with flat aluminium plate and heavy duty U-bolts/exhaust clamps. No rivets have been used in high stress areas, but they are used to hold element sections together which have very low stress. The downside to all this 'over-engineering' is that the antennas are heavy and cumbersome to install. The 4el 20M yagis on 40ft booms are about 120lbs each, but we have had zero failures. Andrew Williamson GI0NWG / AC6WI Homepage = http://www.gi0nwg.freeserve.co.uk/ One of the ZL9CI gang http://www.qsl.net/zl9ci/ -------------------------------------------- Force12Talk mailing list provided as a service by Force 12 Antennas, Inc. Force12 Web Site: http://www.force12inc.com To Submit Message to the List: Force12Talk@qth.com To unsubscribe and view the Message Archive: see http://qth.com/force12/list For problems with the list: contact n4zr@qth.com |