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Re: [TowerTalk] Power Over Coax

Subject: Re: [TowerTalk] Power Over Coax
From: David Gilbert <>
Date: Sat, 23 Oct 2010 17:00:00 -0700
List-post: <">>

It's clear that you're a lot smarter than your engineer.  If he works 
for you, hopefully (for your sake) he's a not an electrical engineer.

Dave   AB7E

On 10/23/2010 4:11 PM, Kipton Moravec wrote:
> I am aware that people use coax for DC power to power electronics.
> I have a 12V 1A (max) motor. It will be variable speed by using PWM
> (Pulse Width Modulation)
> I have an engineer that says I can power the motor over the coax. He
> says no problem -- people power over coax all the time. I do not believe
> him. I can believe it can work for low power stuff, like the LNA for my
> GPS antenna. But a LNA does not generate the same level of noise a motor
> does.
> My concern is that a motor is electrically very noisy. Sparks occur as
> the brushes cross the rotor. This coupled with the inductance of a 1A
> motor and a long cable can produce some serious noise.
> I do not think one can filter it (within a 4 square inches of board
> space) to the point that I would be willing to hook up an HF receiver
> and see if it blows out the front end.
> I thought I would ask the collective wisdom of the TowerTalk people.
> Do you folks think powering this motor over the same coax your HF radio
> is on is doable?
> Kip

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