Hi Bart, Actually, I am NOT using RG-58 coax with my Green Monster coil, unless the high voltage x-ray cable is considered RG-58.? As I was saying, I use the surplus HV cable that runs from the x-ray high voltage generator to the x-ray tube head in a typical medial x-ray machine setup. This cable IS made just like com- mon coax cable, but is considerably more robust. From what I understand, RG-58 is a heavy duty grade of standard coax cable often used to route the RF output of a large radio trans- mitter to the antenna termination, so it would likely be suitable for a Tesla coil transmission line from the HV transformer to the tank circuit for most Tesla coil systems. High voltage x-ray cable consist of ususally 3 seperate inner conductors that are made to carry the low filament voltage to the tube but are also desinged to ride at many kVs in relation to ground for the high voltage. There is a thick insulation barrier (~3/8" thick) wrapped around these three inner conductors and then the grounded braided sheath is wrapped around the outside of this thick insulation barrier. Finally, there is a thin vinyl sleave around the outside of the grounded braided sheath and the total thickness of the cable is usually around 7/8" thick. I leave the RF braid in place, except for pealing back enough at the terminaltions as to prevent flashover (8" to 10" of peelback here). Otherwise, I leave the RF braid in place and let it act as the RF ground return of the tank circuit. That way I only have to run a SINGLE HV transmission line from the transformer to the tank circuit. David Rieben----- Original Message ----- From: "bartb" <bartb@xxxxxxxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx> Sent: Wednesday, June 25, 2008 8:06 PMSubject: Re: [TCML] Where to mount the HV Transformer? Under thecoil orotherwise ?
Agreed! RG-58 is the way I would go. I use it for my antenna (CB), and it's huge and heavy duty. I haven't used it for hv transmission, but I've thought about it.David, thanks for letting us know your success with the Green Monster using RG-58. I've got "lots" of it and should put it to use. I assume you stripped the rf braid back?Take care, Bart David Rieben wrote:Hi Jeremy, You would need the heavy duty coax cable, like RG-58?. That cheap junk that comes to the back of your cable TV box uses foam insulation and would promptly fail under the high voltage stress of Tesla coil transmission line service. I personally like to use surplus x-ray cable for this purpose. It is basically a coax cable on steroids and us usually rated at around 75 kVDC standoff between the inner conductor(s) and the outer braid. It is typically around 3/4" in diameter and I have had very good success using this as a transmis- sion line for the HV from my pole pig to my Green Monster Tesla coil. http://www.dawntreader.net/hvgroup/david/gm.html David Rieben ----- Original Message ----- From: "Jeremy Scott" <supertux1@xxxxxxxxx> To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx> Sent: Wednesday, June 25, 2008 12:36 AMSubject: Re: [TCML] Where to mount the HV Transformer? Under the coil orotherwise ?I read the coax idea off of this site: http://www.pupman.com/safety.htm Somewhere in there it says this:"The transmission line between your high voltage transformer and your tesla coil is another potential source of electrocution. This should be constructed using neon sign wiring (rated to 40 kV) or thick coaxial cable like RG-8A/U or RG-11A/U. If using coaxial cable, use the inner conductor for the high voltage, and strip back the outer braid about 6-12 inches from each end. Connect one end of the braid to your RF ground. Leave the other end unconnected so it does not form a current loop. Some coilers also place their high voltage cables inside a plastic conduit, which is laid on the floor. This also protects the cable somewhat from strikes."I was just wondering if anyone has any experience doing it that way.This is basically the 50 and 75 ohm impedance cable that you can get anywhere. They have a thick PTFE insulation between the core conductor and the braid which I think would be ideal for isolation. The braid being a nice additional safety feature.On the other hand... just don't know.It would be interesting to see just how much voltage it takes to pop one of those cables.--- On Tue, 6/24/08, MIKE BAILEY <m.bailey@xxxxxxxxxx> wrote:From: MIKE BAILEY <m.bailey@xxxxxxxxxx>Subject: [TCML] Where to mount the HV Transformer? Under the coil or otherwise ?To: tesla@xxxxxxxxxx Date: Tuesday, June 24, 2008, 4:42 PM I have my transformers mounted in my control cabinet and run coax cable out to my RSG mounted under the coil , seems to work good no problems so far. I would not connect the braided part of the coax to rf ground , if there are any weak areas in the insulation between the center conductor and the braid or any microscopic holes it will eventually fail and you will have a short to ground and the cable could catch fire. I had a situation where I think there was a break in the center conductor and arcing occured which led to the white cable i was using turning black and started smoking . what I do is just strip the outer layer of plastic and expose the braid and connect it all together with the center conductor and leave lots of space between the 2 cables running out to the coil. Mike _______________________________________________ Tesla mailing list Tesla@xxxxxxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla_______________________________________________ Tesla mailing list Tesla@xxxxxxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla_______________________________________________ Tesla mailing list Tesla@xxxxxxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla_______________________________________________ Tesla mailing list Tesla@xxxxxxxxxxxxxxhttp://www.pupman.com/mailman/listinfo/tesla
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