The math is right. RF will not flow on the inside of a tube. It acts as a waveguide beyond cutoff.
73 Gary K4FMX _____ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Kirk Mefford Sent: Wednesday, March 17, 2010 4:49 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: Copper pipe rather than 2/0 copper wire Not that I think copper pipe is a good alternative to strap, but Gary's math is slightly off. If you are saying 2 inch strap has 4 inches of surface area by counting both sides of the strap, then you need to count both sides of the pipe. Inside and outside surfaces of a pipe equal to 5/8"OD would be very close to the same surface area of a 2 inch strap of the same thickness. Might be ok for grounding a temporary setup or for ground radials on an HF antenna but I wouldn't want to gamble on insurance covering a station using flattened copper pipe as a grounding solution. ----- Original Message ----- From: Gary Schafer <mailto:gascha...@comcast.net> To: Repeater-Builder@yahoogroups.com Sent: Wednesday, March 17, 2010 11:11 AM Subject: RE: [Repeater-Builder] Re: Copper pipe rather than 2/0 copper wire _____ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Jack Davis Sent: Wednesday, March 17, 2010 1:15 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Copper pipe rather than 2/0 copper wire <http://groups.yahoo.com/group/Repeater-Builder/message/98899;_ylc=X3oDMTJxM XBnc3YwBF9TAzk3MzU5NzE1BGdycElkAzEwNDE2OARncnBzcElkAzE3MDUwNjMxMDgEbXNnSWQDO Tg4OTkEc2VjA2Rtc2cEc2xrA3Ztc2cEc3RpbWUDMTI2ODgwMDcyMw--> Re: Copper pipe rather than 2/0 copper wire Posted by: "Eric Lemmon" <mailto:wb6...@verizon.net%20> wb6...@verizon.net <http://profiles.yahoo.com/wb6fly> wb6fly Tue Mar 16, 2010 5:55 pm (PDT) Jesse, Not a good idea. Both NFPA 70 (the National Electrical Code) and NFPA 780 (the Lightning Protection Code) have strict requirements for wire sizes and connection methods. Neither grounding systems nor lightning protection systems may use a soldered connection in the circuit. Perhaps your best course of action is to understand the Code requirements, and construct your system accordingly. Keep in mind the fact that your insurance underwriter may deny any and all claims for damages due to lightning, if your system was constructed in a manner inconsistent with the applicable codes. 73, Eric Lemmon WB6FLY You dont need any solder joints with type K or L soft copper. The material comes is 60 or 100 foot rolls and you just flatten the ends and drill holes for mounting bolts and star washers. ½ inch soft copper is actually 5/8 inch OD and makes a great conductor. The material comes in size up to 2 inch but that gets pretty expensive. This pipe is designed to be buried in the ground so you can be assured it will stand up just fine outdoors. One caution is to anchor it down, swinging in the wind will cause it to break due to repeated flexing. All the normal bend radius for electrical conductors should be observed as lightning does not like to make sharp corners. Jack K6YC
