Thread: Why?
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Old March 27th 07, 08:22 PM posted to rec.radio.amateur.antenna
Wimpie Wimpie is offline
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First recorded activity by RadioBanter: Aug 2006
Posts: 106
Default Why?

On 27 mar, 19:47, "art" wrote:
On 27 Mar, 10:20, (Richard Harrison) wrote:

Jim Pennino wrote:


"Have you ever heard of a helix?"


Most would likely enjoy Kraus` story of his invention of the axial-mode
helix in his 3rd edition of "Antennas". This is a choice book!


Best regards, Richard Harrison, KB5WZI


I have his second edition and I find no mention of radiation from the
beginning where current is applied onwards. Have you found anything
that can
contribute other than empirical grounds? You have avoided the question
so far


Hello Art,

Radiation from accelerating charge is fully understood (from theory
and verified practically), hence antenna theory. When you take the
complete formula for fields (near and far) generated by a short wire
segment (hertzian dipole), you can calculate the far and near field
(magnitude, orientation, phase, etc) from every construction. The only
problem is that you have to know the current distribution in your
construction.

It is not of interest whether the charge is excited by just a voltage
source or EM radiation (like in reflection of waves on conductors and
dielectrics). This is done in many FEM programs.

Of course in many practical circumstances it is easier to use the
"laws" from other people (that are derived from basic theory). One of
the results are the Fresnel formulas for reflection.

When you know the properties of the soil at the operating frequency,
you can calculate the complex surface impedance and hence the complex
reflection coefficient.

Just mentioning words as "curl", "vector", "Gaussian" etc, doesn't
make sense without further information.

Best Regards,


Wim