This is a subject I have some familiarity with. A helix antenna which is
right hand for receive is also right hand for transmit. Think of it this
way. If you have a bolt with a nut on it and you turn the nut to the right
it will move along the bolt away from you. If you turn the bolt around so
you are looking at the other end and turn the nut to the right it will move
away from you. For your transmit antenna the waves are moving away from you
and turning to the right. For the other guy's receive antenna the waves are
turning to the right and moving away from you. It's the same if you think
of yourself as the receive guy and the other guy as transmitting.
Regards.
Max. K 4 O DS.
Email: m...@maxsmusicplace.com
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----- Original Message -----
From: "Dr. David Kirkby" <david.kir...@onetel.net>
To: "Discussion of precise time and frequency measurement"
<time-nuts@febo.com>
Sent: Monday, June 04, 2012 5:30 PM
Subject: [time-nuts] Antenna question about RHCP/LHCP I'm sure a time-nutcan
answer
This is not exactly a time related question, but I'm sure the subject must
be of interest to time-nuts using GPS.
If one transmits from an antenna such as a helical one, RHCP, can the same
antenna be used for reception, or does the helix need to be wound the
other way?
If you google this topic, there seems to be a lot of confusion about
whether the TX antenna and RX antenna need to both have RHCP or whether
one needs to be LHCP and the other RHCP.
Given GPS uses circular polarization, I'm hoping someone here will know.
It would appear there are different definitions of "circular
polarization", with one considering it from the point of view of the
source, and the other considering it from the point of view of the
receiver. The IEEE apparently uses the former, and others (especially
optics) use the opposite.
http://en.wikipedia.org/wiki/Circular_polarization
My aim was to make a gain measurement of two circular polarized antennas.
I have two identical antennas, but are unsure if the signals should be
received strongly, or whether theoretically no signal would be received.
(Of course in practice, one never achieves perfect polarization, so there
will always be a signal detected, even if cross-polarized.
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