Lighting Tower Section Rotation.

Lighting towers are often found for good prices on internet auction sites, and make for very good towers for single HF antennas or lighter VHF arrays.

I bought one of these for just £300 many years ago, and all in all, it must be about 30 years old.  Apart from a few minor crash dents on a couple of braces, it's perfectly serviceable and has withstood ferocious winter gales, over and over.

The only problem with these types of mast is that the sections, especially the inner (top) most one can rotate a few degrees when the wind is stronger than a breeze.  The problem this then gives rise to is an antenna, that has a reasonable amount of mass, that gains momentum.

This puts repeated pulses of high torque stress ('banging stops') on the rotator, which needs to arrest the attempt to turn it.  Whilst most medium to strong rotators can do this comfortably, ultimately, millions of banging stops over years of use will weaken something to the point of failure.

The answer to tower section rotation!

For many years, I've simply used timber wedges, which can be hammered lightly into position.  These work fairly well, but do fall out regularly as the small amount of residual rotation slowly but surely eases them out, or they shrink between wet and dry weather.

I scratched my head for all this time, wondering what kind of adjustable 'wedge' I could come up with that would allow both robust prevention of the rotation and quick removal if needed (such as when a huge gale comes from nowhere, and the tower really has to tilt over.)

A spreader with two runner bars reduces the amount the jaws spread apart under load.

The answer was as simple as it was, thankfully, cheap (£10): a brake pad spreader.  There are very many types of these, and most will probably do, except, perhaps, for the 'silicone gun trigger' type that you operate by squeezing the trigger, rather than a screw thread.  Try to get the ones with two runner bars rather than one, as this helps keep the spreader pads running in parallel.  Use only the 'heel' (the bit nearest the thread) to push the tower sections apart.


Having installed one of these, liberally coated in grease, to push the innermost section against the next one, the very annoying and ultimately damaging rotation has completely been stopped.  Remember to tie a rope and secure the rope to the outside of the tower such that, if it comes off, it doesn't fall on someone's head!