[TowerTalk] Rotor no-no

Robert Nickels W9RAN at oneradio.net
Mon Aug 14 22:57:30 EDT 2006

I learned the hard way that when they say that a HAM-IV type bell 
housing rotor should never be anything but right-side-up, they aren't 
kidding.  I'd just had one rebuilt by Norms Rotor Repair in preparation 
for putting up my new SteppIR.   I folded my Rohn tiltover down and went 
ahead and mounted the "new" rotor.  This means the rotor would be 
upside-down which I knew wasn't recommended,  so I covered it with a 
couple of plastic bags for a few days.  My tower helper and I both had 
to be out of town the next weekend, but I didn't give it a thought since 
I figured there was no way anything could happen.  Wrong!    When I did 
a final test of the rotor before mounting the antenna I had no direction 
indication.  One side of the feedback position pot showed open circuit.  
Worse, when I removed the rotor and turned it over, water ran out - 
evidently my precautions were insufficient.  In the inverted position 
water will gather inside the "bell", resulting in an ohmic path to the 
feedback pot.  I don't know how the water got inside, but I have proof 
it doesn't take much, or much time, for corrosion to ruin the wirewound pot.

Moral of my story - Never NEVER invert a bell housing rotor for any 
period of time!  This is one of those deals where you can only kick 
yourself so many times!  I do have to put in a plug and Thank You to 
RotorNorm, who is going out of his way to help me get this squared-away.

73, Bob W9RAN

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