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[Towertalk] Motor Start Capacitors

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Subject: [Towertalk] Motor Start Capacitors
From: (Bill Coleman)
Date: Mon, 26 Aug 2002 17:49:49 -0400
On 8/8/02 4:22 PM, Joe at wrote:

>Finally, capacitors designed for use with industrial motors are very rugged.
>The ones that  come from a source like Gainger are expected to live in the
>cruel, harsh external world.  (Go look at you outside A/C unit's fan motor
>cap.) If properly installed, they will outlast most amateur antennas.  We've
>had them on towers for over 15 years with no failures.

When I put up my tower last year, I refurbished a Ham-M rotator whose 
capacitor had gone bad. (Amazing that his 27-year old piece of equipment 
worked otherwise flawlessly) Rather than mess with the control box, I 
mounted the replacement cap on the tower, near the rotator.

I didn't use a Grainger industrial device. Instead, I bought a 150 uF, 
100 V non-polarized cap from In fact, I bought TWO, just 
in case one blew up on me. 

To allow for rotator disconnect, I used a couple of trailer hitch 
electrical connector pairs. This gave me 8 conductors worth of 
weatherproof connectors. (One is wired up opposite the other, so you 
can't cross them up.)

One set of connectors is wired to the bottom of the rotator. The other is 
wired into a 4" square NEMA box, which houses the capacitor as well. A 
U-bolt holds the box to the tower leg. Standard Wireman R1 rotator cable 
runs from the box back into the shack.

This arrangement has been flawless. The smaller Radio Shack caps get warm 
during rotation, but they haven't failed on me yet. The Grainger devices 
would last forever.

Bill Coleman, AA4LR, PP-ASEL        Mail:
Quote: "Not within a thousand years will man ever fly!"
            -- Wilbur Wright, 1901

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