Kent,
I ran across the following link that describes a home made fence charger. The author also talks a bit about grounding. After thinking about Peter's situation I bet he floated the coax shield, or had a poor ground return to the earth. Then again lets suppose he had both a good earth ground at the fence feed point (multiple ground rods bonded together), and the coax shield was grounded at the same end. Would the fast pulses result in ringing of the unterminated 75 ohm transmission line that might be several wavelengths long at the pulse decay frequency? I bet that coax would take it for a while before arcing internally, and maybe be pretty nasty to be around. Then again, maybe my Egg-Nog has been spiked! ;=) scroll down to pages 3, 4, 5 at the following link: http://www.homepower.com/files/electricfence.pdf Regards, Jim JKO -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of KA5MIR Sent: Sunday, December 24, 2006 9:12 AM To: amradio@mailman.qth.net Subject: Re: [AMRadio] HV Wire 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. Kent/KA5MIR 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 > JKO ______________________________________________________________ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.432 / Virus Database: 268.15.26/600 - Release Date: 12/23/2006 4:47 PM -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.432 / Virus Database: 268.15.26/600 - Release Date: 12/23/2006 4:47 PM ______________________________________________________________ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
