To quote Jasik's treatment of Kraus's work:
"There are two kinds of circular polarization, right-hand, and left-hand.
Either
type may be generated by a helical beam antenna, depending on the manner in
which
the helix is wound. A helix wound like a right-hand screw radiates or receives
right-hand circular polarization..."
Pretty clear in Jasik. I have to believe that Kraus was able to make a
statement
with a similar level of clarity somewhere in his book... but I don't have a copy
on hand to test my beliefs.
As to the thread handedness: That is pretty old terminology that has been
around
since the first blacksmith tried to describe how he made his screws to another
blacksmith.
In any case, the "handedness" of a circularly polarized wave is really just a
convention. If the person discussing the principal understands the principal,
he should arrive at descriptions that are self consistent. Believing that a
RHCP antenna transmits with a right hand helix, and receives with a left hand
helix is not being consistent. Either the frame of reference is inconsistent,
or the understanding is inconsistent.
Right?
-Chuck Harris
PS, I don't see this as arguing, just two friends having a discussion.
Rex wrote:
I took a scan through Kraus "Antennas" since he did much of the definitive work
on
Helical antennas. In his chapter on Wave Polarization he gives a mathematical
definition of Left- and Right-circular polarization, then quickly mentions that
the
IEEE definition is the opposite. He has a footnote: "This IEEE definition is
opposite
to the classical optics definition."
So it seems our current antenna engineering uses the IEEE definition for RHCP
and
LHCP, but earlier work on EM wave theory had defined right-circular and
left-circular
exactly reversed from IEEE. So, combine that with the reflection flipping and
it is
not hard to think why there might be confusion.
I looked all around for a simple definition of the RH, LH quality of the wave
from a
helix antenna. I assume I might have extracted it from pages of formulas and
theoretical explanations, but why not just clearly state it in a book that is
largely
about helical antennas. Somewhere else (in Kraus) I read that the IEEE
definition of
a RHCP or LHCP wave from or to a helical antenna had the same handedness as the
helix
of the antenna. Unfortunately in that writing he did not bother to explicitly
mention
what he meant by the handedness of a helix. I assume he meant it to be the same
as
the handedness of a screw, but he didn't say that, so once again, a missed
opportunity.
I'm not arguing with you, Chuck, just pointing out why there might be room for
confusion in some circles. (Pun intended.)
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