On Wed, 29 Mar 2006 15:36:08 -0500, John Popelish
wrote:

I appreciate you taking the time and effort to try to straighten me
out on this, but if there is no magnetic lines broken (whatever that
means) why use a magnetic core? Why wouldn't disks of carbon work
just as well. They are certainly resistive.

Hi John,

Breaking magnetic lines (flux) is a commonplace of fields, motors, and
generators. A single wire that passes through a bead, torus, or core
will build a magnetic field concentrated within that structure when
the circuit is completed outside of it. The flux lines of half the
loop will penetrate the core to reach the other half of the loop. The
core breaks the magnetic line of flux. The dissymmetry of penetration
builds a magnetic field in the core.

However, when the complete current loop is within the same structure,
the flux lines do not fulfill that same function. The flux lines that
do emerge from the tightly bound wires can be said to penetrate the
torus, but here the symmetry creates bucking fields, the net effect is
as though there was no core at all (except to add capacitance).

Both models attempt to stimulate a current within the toroid, the
common mode of the single wire model above is lossy, the differential
mode of the twin line model that followed sees nothing. Superpose
these two for the coaxial solution.

To put this to a test. Load up your rig, through a SWR meter to a
dummy load using two short connection wires (this will undoubtedly
require adapters and such to break out both paths). You should note a
1:1 indication. Place two #75 beads on ONE wire. You should note a
2:1 indication. You have just inserted 40 to 60 Ohms of additional
resistance into the circuit. Now, move the same two beads to
encompass BOTH wires. This should return the SWR meter to a 1:1
indication.

73's
Richard Clark, KB7QHC