Help me choose an antenna tower!

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by UT2UM, Jul 31, 2021.

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  1. NG1H

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    Ah. In that case I would maybe lean towards the Rohn 25. One of the difficulties with worm-style rotators is installation can be difficult due to the motor sticking out to the side, especially if the plates are already welded into place as is the case with (some of?) the jack-up towers. If possible one design criteria could be how easy it is to install by sliding it in from the side.

    A few other design issues that I would consider:

    The Alfa-Spid design is a pain because you have to raise the mast whenever you install or remove it. Also the tubes warp slightly when welding. If your mast is close to the ID of the rotator over time it can get stuck and impossible to remove. Then you have to cut off the mast and weld another receiving tube on top of the old one if you ever need to work on it. All the rest use a clamp that can be dismantled. It is a weaker design but eliminates these problems.

    With a worm-type drive you don't need a braking system. If possible this is what I would use. One idea, though it does increase cost, is to use either a second worm system or beveled gears to keep the motor parallel to the mast and not sticking out the side.

    Both the Alfa-Spid and the Italian rotator have problems with water ingress into the electronics. With the Alfa-Spid the electronics are off to the side and the easy solution is to smear it with lots of sealant. With the Italian model the electronics are in the casing and so when the shaft seal leaks water gets into the electronics. The A-S shaft may leak also but it will only get into the gearing and that part is PACKED with grease.

    Speaking of grease consider erring on using grease designed for hot weather. These mounts have enough torque that the grease gaining viscosity in cold weather isn't a problem (that I've heard of) but I have seen non-ham systems that were designed in northern countries that had the grease running out of them when used in tropical climates.

    The two main orientation coding methods used are either using a rheostat mounted to the main shaft or using hall effect sensors on the motor shaft. The former wears out and requires maintenance. The advantage is that when working you always have absolute position. The latter seems to last forever (or a very long time) but you are relying on your controller to keep track of where you are pointed. The advantage of this one in addition to longevity is that if you ever need to reset your positioning it is a simple change in the control box. I would recommend the motor shaft method.

    Last of all I would consider using voltages and readouts compatible with existing systems. This way you have 3rd party controllers available from day one.

    Good luck!

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