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Re: [TowerTalk] Prop Pitch Motor

To: "Tower and HF antenna construction topics." <>
Subject: Re: [TowerTalk] Prop Pitch Motor
From: jimlux <>
Reply-to: "Tower and HF antenna construction topics." <>
Date: Sun, 14 Mar 2010 22:13:17 -0700
List-post: <">>
Gene Fuller wrote:
> What is the maximum DC voltage used successfully/recommended for one of the 
> "small"  PPM's ?  What speed was accomplished and how was the brush life at 
> that voltage ?
> I 'm building a power supply to put at the base of the tower and can change 
> the voltage from about 30 to 48 volts in 6 volt steps. Cable to PPM will be 
> 100 feet of 3-#12's. I'm figuring about 0.5 ohms and about a ten amp demand  
> i.e. a 5 volt drop.
> Any suggestions will be greatly appreciated.
> Thanks,
> Gene / W2LU

Handy to remember..

AWG 10 wire is about 0.1" in diameter and 1 ohm/1000 ft.

For every 3 gauges, the resistance doubles.
For every 10 gauges, the resistance is x10.

So.. 200 ft of AWG 10 (up and back) would be 0.2 ohms.
Going to AWG 12 is a bit less than doubling (0.4 ohms)

Your estimate of 0.5 ohms for AWG 12 is a bit pessimistic. (assuming a 
single conductor up and back)

If you were thinking triple AWG 12 up and triple AWG 12 back, you'd be 
much less than 0.2 ohms total, since 3 AWG12s is almost twice the cross 
sectional area of a single AWG10.

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