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[email protected] · August 3rd 15, 07:27 PM posted to rec.radio.amateur.antenna

rickman wrote:
On 8/3/2015 1:44 PM, wrote:
Jeff wrote:

This has been explained previously. A dipole is not balanced when it is
connected to the coax. The shield outer surface presents a third
element which makes the shield side of the dipole different from the
center conductor side. In the case of the resistor the current flowing
in one side must flow out the other, so it is balanced no matter what.
The dipole has no such requirement. If you restrict the current running
into one side and not the other it can do nothing about it.

No, a dipole is still balanced, the coax outer does not create a 3rd
element other than by coupling. If the coax is taken off at right angles
the coupling will be low as similar to both elements of the dipole. The
dipole will never be perfectly balanced but can be a very close
approximation.

It your contention about the coax acting as a 3rd element were true then
there would be severe distortion of both the impedance of the dipole and
to it radiation pattern. This is not seen in practice and it is also
demonstrable that there is little current flow on the coax outer when
the dipole is well matched to the coax.

Jeff

The coax shield does create a 3rd element but the effect of it highly
depends on on the length of the coax and whether or not the shield is
grounded somewhere along the way.

The effect can be anywhere from negligable and barely measurable to
extremely significant and can be seen with an antenna modeling program.

Let me summarize...

a) No current on shield outer surface

b) Current on shield outer surface

C) Any conceivable combination of the above

Your answer is c). Thanks for playing!

Nope, just yet another knee jerk response.

If you had actually read and understood what I wrote, the only possible
answer is b.

The only thing in question is the magnitude of the current; that there
is a current is a given.

--
Jim Pennino