[AMRadio] HV Wire

KA5MIR ars.ka5mir at gmail.com
Sun Dec 24 10:12:08 EST 2006

Haven't messed with them in a long time, but the few I've worked with used an 
autotransformer or coil where a battery or low voltage was connected across 
the primary and the fence and a ground were connected across the secondary.  
A relay supplied power to the coil until it was charged, (usually about a 
second) and when the relay interrupted the primary, the collapsing field put 
a big pulse of energy on the wire.  Same principle as the ignition system of 
a vehicle ...and DC powered relay kickback.


On Saturday 23 December 2006 20:12, Jim Candela wrote:
> Peter,
>     I am wondering how electric fence chargers work. I once heard that
> they pulse the HV on and off. I assume you grounded the coax shield near
> your home or barn yet the coax was still hot anywhere it touched the
> earth?? I don't see how that could be unless the coax braid was floating,
> and the HV pulsing was coupled to the shield from the cable capacitance
> per foot (~ 20pf/'). If the shield was grounded that capacitance would
> also charge to the peak value of the pulsed DC, and might end up changing
> the whole situation should a cow brush up against the wire. The 'danger'
> factor of the fence might  go up a notch or two this way.
>    I'd like to hear more of your electric fence story.
> Regards,
> Jim

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