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Re: [TowerTalk] Rotator clamp help

To: Anthony DeBiasi <k2sgcw@gmail.com>
Subject: Re: [TowerTalk] Rotator clamp help
From: kq2m@kq2m.com
Date: Mon, 23 Sep 2024 21:48:14 -0500
List-post: <mailto:towertalk@contesting.com>

Hi Tony,

I have not used a K7NV mast clamp so I can't speak to it's performance. But I have been using an Orion 2800 on my top 20 - 5L LJ105CA on a 35' boom at 130' for the past 15 years. In all that time with two hurricanes, 1 tornado, and dozens of 80+ mph wind gusts, ice storms, Nor'easters, etc. the mast has loosened up only twice.

My antenna is clamped against both the mast as well as the boom and balanced for weight at the point at which it is mounted on the boom. I believe that the special truss and torque clamp apparatus that I made and currently use may have something to do with the clamps longevity as it has significantly reduced the rocking of the antenna during periods of extremely high winds.

I have not found it necessary to purchase a K7NV clamp but those who have used one speak very highly of it. The main issue is that the mast is circular and the stock Orion clamp is more in the shape of a "V" which ensures that there is far less than the maximum possible surface area of the clamp coming into contact with and gripping the mast. Weather, topography, wind and other factors come into play so that no two qth's will experience the same set of challenging conditions on the clamp. My qth is particularly windy and turbulent and prone to exceptionally violent storms at times so it takes a toll sooner rather than later on anything up on my towers. I'm happy with the performance of the stock Orion clamp but all you need is one incident of catastrophic clamp failure to ruin your day. ;-)

73 and GL!

Bob, KQ2M


On 2024-09-23 14:44, Anthony DeBiasi wrote:
I am presently using an older M2 Orion rotator. After 22+ years it has failed and needs replacing. When I moved to Florida 3 years ago, instead of using the supplied stock mast clamps I purchased a K7NV mast clamp which some of you may be using. The K7NV mast clamp definitely prevents slippage although in 18 years at my last QTH which was fairly windy the stock mast clamps only slipped once during a hurricane which was easy to correct with the Green Heron RT-21 controller and snugging up the clamp bolts. I should mention the rotator is on a 86’ Tashjian tower that nests to 23’ and is fairly easy to access.

I am trying to decide if it would be better to replace the K7NV mast clamp with the stock M2 mast clamps that are more likely to slip. Why would I considering the change, to possibly put less stress on the M2 rotator. On the tower from the bottom up there is a JK-Mid Tri/40, a 5el M2 6m yagi and on top is a WARC JK1217. Although I live in Florida, I am located about 15 miles inland and 35 miles north of Tampa. We do get a lot of Thunderstorms in the summer but the wind has been far less than I experienced in Northern NJ and Southern NJ.

Would appreciate the advice of anyone who has experience with either the stock M2 clamps or the N7NV clamp. I know you can put a pin through the clamps and mast but I wouldn’t suggest that.

73, Tony K2SG
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