"christofire" wrote
...

"Richard Clark" wrote in message
...
On Tue, 15 Sep 2009 11:52:19 +0100, "christofire"
wrote:

No, you have it wrong again - the current must be zero at the ends, there
is
nowhere for it to go, and there cannot be acceleration of charge is
there's
no current. Please go away and read some books and the NEETS module to
which I provided the link.

Chris

Hi Chris,

This mistake is being compounded daily, so it seems. The "absence" of
current on any particular portion of the antenna is the superposition
of two currents flowing - hence the term "standing wave antenna."
Hence there is something of a paradox that where two currents reside
(the metal elements are continuous and conductive) it is said no
current flows. There is a correlation between this superposed
solution and the pattern of the far-field pattern but that does not
lead to the conclusion that there is no "acceleration" of charge at
the ends. After-all, the abundant alternating voltage at those same
ends is also charge, n'est pas? It could be as easily argued that
superposed voltage nodes also define the pattern of the far-field
pattern.

73's
Richard Clark, KB7QHC


Well, the moment of a section of a dipole is proportional to the average
net current on it and it's the integral of the moments at a point of
inspection that yields the radiation pattern. In my simplistic way of
thinking, if the moment of the end sections is zero, or as close as makes
no difference, then there's no contribution to the pattern from there, so
there's no radiation from there. Someone else who posted here a while ago
used the term 'unopposed' current which is useful because it's the basis
of why twin-wire transmission line, driven differentially, is a poor
radiator - put another way, the moment at any point is close to zero.
Alternatively, if there's no radiation from a 'source' then there can't be
any unopposed current there.

I wouldn't contradict what you say about there being a collection of
charge at the ends of a dipole during each cycle, especially when it has
added capacitance (e.g. a 'hat' or the top of a 'Tee'), but the current in
a symmetrical hat is fully opposed and, as I noted before, the current at
the end of the conductor must be zero - by the definition of conduction.

I believe there is danger in trying to relate radiation to voltages rather
than currents, arguing that displacement current causes radiation.
Therein lies the fallacy of the CFA, E-H antennas, and associated efforts
at re-writing of Maxwell's equations, which are all being demonstrated as
bunk. Also, this appears to be the basis of Mr. Bialek's lecture series.
If you wish to argue 'that superposed voltage nodes also define the
(pattern of the...sic) far-field pattern' then I won't stand in your way
... but I probably won't believe you.

So I will start "Mr. Bialek's lecture series" as a new topic.
The first will be on a "standing waves". A will try to explain the paradox:
"Hence there is something of a paradox that where two currents reside (the
metal elements are continuous and conductive) it is said no current flows
(R. Clark).
S*


Chris