View Single Post
  #37   Report Post  
Old January 15th 09, 10:53 PM posted to rec.radio.amateur.antenna
Art Unwin Art Unwin is offline
external usenet poster
 
First recorded activity by RadioBanter: Mar 2008
Posts: 1,339
Default Contrary current flow within a radiator

On Jan 15, 3:48*pm, Jim Lux wrote:
Richard Fry wrote:
On Jan 14, 12:07 am, Art Unwin wrote:


It has not yet been proven that current does not flow thru
the center of a radiator.


Assuming that significant r-f current exists at the center of a
radiating conductor, where does it go when it reaches the end of that
conductor?


Ahh.. the famous "boundary condition"..

Say you've got a big bar 100 feet long and a foot in diameter, and
you've induced a rf current along it by some means. *All those equations
* with the Bessel functions tell you the magnitude and phase of the
current in some infinitely thin slice in the middle.

But, at the end, those equations don't hold. *Essentially, the "reverse
current" flows radially across the end and forms part of the "forward
current" on the surface.

I doubt there is a good analytical solution of this. *There's probably
some decent approximations (within 5% or something), but anyone who
really cares is going to do a FEM analysis of some sort and solve the
problem numerically.

RF



Hmmmm

I think anybody with a education could apply vectors to a full wave
RESONANT radiator with charge and applied current such that Newton's
laws can be shown as being satisfied
Why would anybody shy away from that since we know that there is no
current/ charge flow
on the inside so the vectors will balance. Is there any disagreement
with that aproach.
If so why?
It WILL show agreement with the groups aproach with respect to zero
current / charge flow in the center of a radiator which should make
you all feel good.
Art


Art