[Elecraft] RF on pipes

2011-07-09 Thread Clint
This is a bit OT but it does concern my K3. Hopefully this will not open too big of a can-o-worms. As an experiment to try and achieve a very low impedance ground system, I am using 1 inch rigid copper tubing for my station and Vertical Antenna grounds and ½ copper refer tubing to tie together

Re: [Elecraft] RF on pipes

2011-07-09 Thread Fred Jensen
On 7/9/2011 10:02 AM, Clint wrote: ANYWAY, I know that RF travels on the outside skin of a conductor. My question is: Does it also travel on the inside skin? Only if you inject it there [e.g. a copper plug into the end of the pipe that connects with the inside only]. Similar to coax which

Re: [Elecraft] RF on pipes

2011-07-09 Thread Geoffrey Mackenzie-Kennedy
Evening Fred, If the pipe is OPEN at its ends, would not the current flowing on the outside of the pipe fold over at the end of the pipe and continue to flow on the inside skin? The reverse, if you like, of the situation where a coax feeder is used to feed a dipole / doublet. 73, Geoff GM4ESD

Re: [Elecraft] RF on pipes

2011-07-09 Thread Ian White GM3SEK
Geoffrey Mackenzie-Kennedy wrote: Evening Fred, If the pipe is OPEN at its ends, would not the current flowing on the outside of the pipe fold over at the end of the pipe and continue to flow on the inside skin? The reverse, if you like, of the situation where a coax feeder is used to feed a

Re: [Elecraft] RF on pipes

2011-07-09 Thread Geoffrey Mackenzie-Kennedy
Point taken Ian, grey cells in reverse gear here :-) 73, Geoff GM4ESD On July 09, 2011 at 19:17Z, Ian White GM3SEK wrote: No - HF fields cannot propagate inside an open tube because it behaves as like a 'waveguide beyond cutoff'. Any HF EM field injected into the open end will only

Re: [Elecraft] RF on pipes

2011-07-09 Thread Jim Dunstan
Yes, as in coax for an example. when transmitting eg via coaxial cable which is properly installed the rf currents flow on the inside surface and not on the outside surface. I mention proper installation .. In which case steps are taken to keep the inside and outside surfaces separate (at

Re: [Elecraft] RF on pipes

2011-07-09 Thread Nick-WA5BDU
A hollow conductor is not analogous to a coaxial cable. It has no center conductor. In the case of the hollow conductor (copper pipe), current will flow on the outside surface only. Skin effect still applies and works exactly as if the conductor were solid. 73- Nick, WA5BDU On 7/9/2011