Topband: Ladderline

[Doug Waller]

DK6NP:
> You should be able to use a ferrite choke also with the ladder line. You will
> have to use a larger toroid, also the ladder line itself will probably not go
> through the toroid, so you have to use two single wires.  Mechanically it
> does not look as nice as the coax solution, but electrically it is equivalent.

Given that RF only travels on the surface of a conductor, I believe a ferrite
choke placed on the individual wires of a ladder line would choke all RF current
flow, allowing only DC, if present.

Coaxial cable has some very interesting properties which will allow two
completely different RF current flows on the shield, one on the inside, the
other on theoutside.  This is how cancellation of radiation can take place
between the equal and opposite RF currents of the center conductor and the
inner surface of the shield, while a common mode RF current flows on the
outer surface of the shield.

How a ferrite choke placed on the outside of the coax shield chokes only the
outer surface RF current flow, and not the inner, is beyond me, but it must
happen if the outer surface RF is choked while the inner RF continues to be
equal and opposite phase of the center conductor.

TBDX, om Doug / Nx4d




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