[TowerTalk] [Bulk] Re: antenna choices for K4XS

[Grant Saviers]

One hint for putting together many antennas with clamps so they stay 
together (whether stamped or hose clamps, e.g HyGain, CC, etc).

One poster said his TH7 fell apart.  I've had two which survived 5 
serious hurricanes between them without any problems.  What I found was 
the clamp forces relax after the initial tightening.  HyGain stamped 
element clamps or telescoping tube hose clamps, it makes no difference.  
So after the initial torque of the bolts, let the antenna stabilize for 
a few days.  Best if it can be exposed to temperature cycling, e.g. hot 
day sun and cool nights.  After several cycles go back and torque all 
clamps and fasteners, it is amazing how much they relax.  (don't forget 
to lube stainless bolts or the torque is meaningless if they seize).

Of course, it's best to use a calibrated means of torque setting, but 
those aren't in many ham toolboxes for smaller than 1/4-20 fasteners.

One commercial product I was responsible for had required clamping 
forces near the yield points of the very high strength fasteners but the 
parts would still move in service.  So we set up temp cycling 
ovens/coolers to cycle the assembly and then a final torque to the limit 
solved the relaxation problem.

http://www.mountztorque.com/learning-center/article/techniques-reduce-joint-relaxation-fastened-joints

Grant KZ1W