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Old June 5th 07, 04:48 PM posted to rec.radio.amateur.antenna
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Default Determining Total Gain of an Antenna

On May 30, 10:47 am, art wrote:
On 29 May, 19:47, (Richard Harrison) wrote:

Matt Brenenman wrote:


"When I think of how a field induces a voltage, I think of voltage as
being proportional to norm of the field."


OK. Terman wrote on page 2 of his 1955 opus:
"The strength of the wave measures in terms of microvolts per meter of
stress in space is also exactly the same voltage that the magnetic flux
of the wave induces in a conductor 1 m long when sweeping across this
conductor with the velocity of light."


Since Matt mentions circular polarization, one of the problems on page
50 in Kraus` 3rd edition of "Antennas" is notable. It states:
"1-16-2 More power in C.P. Show that the average Poynting vector of a
circularly polarized wave is twice that of a linearly polarized wave if
the maximum electric field E is the same for both waves. This means that
the medium can handle twice as much power before breakdown with circular
polarization (CP) than with linear polarization (LP)."


Best regards, Richard Harrison, KB5WZI


Richard,
I am trying to decipher the above so my comments may well not be
relavent to what you are actually saying.
It is a given that far field circular polarisation
results in a 3 db loss with respect to radiation compared to other
polarisations. But one cannot from this assume that radiation
from a radiator changes with respect to the designed polarization.
When current is applied to a radiator in a time varient condition
the vectors involved cannot change.
The three phases of radiation are current application and electron
emmission,formation of the near field and finally formation of the
far field.
I fail to see how vectors formed in the initial stage which can
be seen as a Poyntings explanation changes or depends upon
future formations of the ensueing radiation waves.
Since the poster is interested in mathematicalanalysis of radiation
he must obviously realise that the Laws of Conservation must be held
and it woulkd appear that some confusion has been injected into his
problem.
Art


Thank you for the responses. I've been to an out of town symposium the
last week, and I haven't had time yet to sit down and think about them
much. I'll look at the texts suggested and then perhaps I can make a
considered reply ;).

Thank you once again,

M

 
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