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[TowerTalk] Rotator problem solved

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Subject: [TowerTalk] Rotator problem solved
From: (Dan Violette - KI6X)
Date: Mon, 3 Nov 1997 11:44:36 -0800
This reminds me of my youth.  I had an old CDR rotator that needed a cap.  
I could only find eletrolytics big enough at the parts store.  Put it in 
(not realizing it was A/C, I was in high school at the time) and stood a 
few feet away when I was testing it on the bench.  Within a few seconds 
KABLAM and paper dust was everywhere (as well as acid mist as I learned 
later).  I learned about non-polarized electrolytics fast.

Dan  KI6X

On  3 Nov 97, David O. Hachadorian wrote:

On Mon, 3 Nov 1997 15:42:58 +200 "Chris R. Burger"
<> writes:


>Only question remaining: must I really buy the 'proper' cap ? I used 
>old 100uF 100V electrolytic cap from my junk box and it seems to work
>fine. The 'proper' cap is  approximately $ 15 from the local HyGain 
>supplier. Can the electrolytic damage the motor ?

Electrolytics have a low breakdown voltage in the reverse
direction. There is a way to use two electrolytics
back-to-back, with shunting diodes, but you
would be better off buying a capacitor designed for AC use. In the
states, one can go to any motor shop and get a 120V AC capacitor for
about $4, but it will be physically larger than Hy-Gain's and will
have to be wired in. The capacitance value is not critical. Stay with
Hy-Gain's value, or the next larger size available. I remember doing
the phase shift calculations about 20 years ago to make that
determination, but remember only the general conclusion, not the
hard numbers of what values work. 

Dave Hachadorian, K6LL
Yuma, AZ

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-- Dan Violette    Amateur Radio: KI6X   E-mail: --

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