Antenna question about RHCP/LHCP I'm sure a time-nut can answer
I guarantee you it doesn't cause any controversy among those that
use circularly polarized antennas.
That the polarization changes from RHCP to LHCP when reflected is
certainly the cause of some confusion about the antennas. A RHCP
antenna that directly emits a wave towards the source will become a LHCP
antenna if it is illuminating a parabolic dish.
The easiest way to think about it is to mentally think of the path from
the transmitter to the receiver as a very long piece of threaded rod, and
the wave being emitted as being a nut traveling on the rod. No matter
which side of the rod you are observing from, you will observe a nut
traveling away from that end turning in the same direction (clockwise
for RHCP).
Another point of confusion could be that if you are standing at the
transmitter watching the nut travel away from you, it will be rotating
clockwise.... but if you are standing at the receiver watching the
nut traveling towards you, it will be rotating counter-clockwise.
Both cases are RHCP.
If I hired an engineer to work on circularly polarized antennas and he
didn't know this, I too would be thinking of firing him!
-Chuck Harris
David Kirkby wrote:
On 5 June 2012 01:12, Dave Martindaledave.martindale@gmail.com wrote:
I don't think that's correct.
This is a funny topic. No matter where see it discussed, there are
people with different views on it. I looked on the edaforum
http://www.edaboard.com/forum26.html
and found a thread (can't find it now unfortunatey), where someone was
adament they needed to be one way (I forget whether both RHCP or
RHCP+LHCP), and someone else was adament a colleague nearly lost his
job after making that mistake. I think there was about a 50:50 mix of
views on the topic
The easiest way to think about it is to mentally think of the path from
the transmitter to the receiver as a very long piece of threaded rod, and
the wave being emitted as being a nut traveling on the rod.
Ah, and each of the photons then becomes a time nut.
/tvb
Tom Van Baak wrote:
The easiest way to think about it is to mentally think of the path from
the transmitter to the receiver as a very long piece of threaded rod, and
the wave being emitted as being a nut traveling on the rod.
Ah, and each of the photons then becomes a time nut.
Of course!
I forgot to mention that the nut is spinning, not the rod... So it
is not just a timenut, but a spinning timenut.
-Chuck Harris
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.)
On 6/5/2012 6:23 AM, Chuck Harris wrote:
I guarantee you it doesn't cause any controversy among those that
use circularly polarized antennas.
That the polarization changes from RHCP to LHCP when reflected is
certainly the cause of some confusion about the antennas. A RHCP
antenna that directly emits a wave towards the source will become a LHCP
antenna if it is illuminating a parabolic dish.
The easiest way to think about it is to mentally think of the path from
the transmitter to the receiver as a very long piece of threaded rod, and
the wave being emitted as being a nut traveling on the rod. No matter
which side of the rod you are observing from, you will observe a nut
traveling away from that end turning in the same direction (clockwise
for RHCP).
Another point of confusion could be that if you are standing at the
transmitter watching the nut travel away from you, it will be rotating
clockwise.... but if you are standing at the receiver watching the
nut traveling towards you, it will be rotating counter-clockwise.
Both cases are RHCP.
If I hired an engineer to work on circularly polarized antennas and he
didn't know this, I too would be thinking of firing him!
-Chuck Harris
David Kirkby wrote:
On 5 June 2012 01:12, Dave Martindaledave.martindale@gmail.com wrote:
I don't think that's correct.
This is a funny topic. No matter where see it discussed, there are
people with different views on it. I looked on the edaforum
http://www.edaboard.com/forum26.html
and found a thread (can't find it now unfortunatey), where someone was
adament they needed to be one way (I forget whether both RHCP or
RHCP+LHCP), and someone else was adament a colleague nearly lost his
job after making that mistake. I think there was about a 50:50 mix of
views on the topic
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Hi:
I've used an L band amplifier and a passive GPS receive antenna as the transmitting antenna to make a GPS repeater. It
was feed from an outside GPS antenna.
This allowed having a number of hand held GPS receivers sitting side by side working inside.
Have Fun,
Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/Clarke4Congress.html
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.)
On 06/ 5/12 04:06 PM, 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."
That's basically what Wikipedia says about the optics. They don't reference it,
so if it is referenced in Krauss, that would be a worthwhile reference.
Most antenna people seem to accept the standard definitions as being "IEEE
Standard Definitions for Terms of Antennas IEEE Std 145-1983"
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'm not saying Chuck is wrong about one needing the same sense at each end, but
I would disagree with him when he says "I guarantee you it doesn't cause any
controversy among those that use circularly polarized antennas." There certainly
is a lot of confusion over this topic, even among people who design them. I
don't think the confusion is related to reflections (everyone seems to know
that) and I don't think it's related to different conventions either.
I was going to try to simulate this by putting two helix antennas and coupling
them. But setting that up is a lot more difficult for me than just building
three antennas.
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.
Quality of polarization is a very complex topic. See the paper:
"The definition of cross polarization"
Antennas and Propagation, IEEE Transactions on
Date of Publication: Jan 1973
Author(s): Ludwig, A.
California Institute of Technology, Pasadena, CA, USA
Volume: 21 , Issue: 1
Page(s): 116 - 119
I've reprinted the abstract below for completeness, though you can read it on
the IEEE site without paying.
Abstract
There are at least three different definitions of cross polarization used in the
literature. The alternative definitions are discussed with respect to several
applications, and the definition which corresponds to one standard measurement
practice is proposed as the best choice.
I printed off a copy of that paper with the intension of trying to understand
it. I think the maths gets a bit heavy for me, but the more difficult problem is
I was unable to read the small symbols on A4 paper. So it looks as though I'll
have to read it on a computer and hope the quality is good enough.
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.)
One method of logically arguing for both antennas to be the same is reciprocity
theorem. So I think Chuck is right on the engineering facts, but is wrong about
the level of confusion it causes. I wish I could find the post on the EDA forum,
as there were many people making arguments for both cases.
Dave
Hi David,
Since I apparently have no cred, I can give you a quote from Jasik:
"A right hand helical antenna transmits or receives right-hand
polarization while a left-hand helical antenna will transmit or
receive left-hand polarization." Jasik, "Antenna Engineering Handbook",
First Edition, p17-3.
Which seem fairly clear to me.
In my experience, there really is no confusion about that among
competent antenna engineers... among those less schooled in the
subject, any amount of confusion is not only possible, but probable.
I could see how one could be confused about the definition, as it is
purely a matter of convention. That RHCP is defined as the wave
propagating in the clockwise direction as viewed from the source could
just as easily have been defined as being viewed looking towards the
source... but, since the current convention was defined by the IRE
more than half a century ago. It shouldn't be all that controversial
anymore.
-Chuck Harris
Dr. David Kirkby wrote:
On 06/ 5/12 04:06 PM, 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."
That's basically what Wikipedia says about the optics. They don't reference it, so if
it is referenced in Krauss, that would be a worthwhile reference.
Most antenna people seem to accept the standard definitions as being "IEEE Standard
Definitions for Terms of Antennas IEEE Std 145-1983"
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'm not saying Chuck is wrong about one needing the same sense at each end, but I
would disagree with him when he says "I guarantee you it doesn't cause any
controversy among those that use circularly polarized antennas." There certainly is a
lot of confusion over this topic, even among people who design them. I don't think
the confusion is related to reflections (everyone seems to know that) and I don't
think it's related to different conventions either.
I was going to try to simulate this by putting two helix antennas and coupling them.
But setting that up is a lot more difficult for me than just building three antennas.
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.
Quality of polarization is a very complex topic. See the paper:
"The definition of cross polarization"
Antennas and Propagation, IEEE Transactions on
Date of Publication: Jan 1973
Author(s): Ludwig, A.
California Institute of Technology, Pasadena, CA, USA
Volume: 21 , Issue: 1
Page(s): 116 - 119
I've reprinted the abstract below for completeness, though you can read it on the
IEEE site without paying.
Abstract
There are at least three different definitions of cross polarization used in the
literature. The alternative definitions are discussed with respect to several
applications, and the definition which corresponds to one standard measurement
practice is proposed as the best choice.
I printed off a copy of that paper with the intension of trying to understand it. I
think the maths gets a bit heavy for me, but the more difficult problem is I was
unable to read the small symbols on A4 paper. So it looks as though I'll have to read
it on a computer and hope the quality is good enough.
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.)
One method of logically arguing for both antennas to be the same is reciprocity
theorem. So I think Chuck is right on the engineering facts, but is wrong about the
level of confusion it causes. I wish I could find the post on the EDA forum, as there
were many people making arguments for both cases.
Dave
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
On 06/ 5/12 12:26 AM, Magnus Danielson wrote:
On 05/06/12 00:30, Dr. David Kirkby wrote:
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.
They would have to have opposite rotation.
The waveform rotation will follow the transmitter antenna into the
receiver antenna. The receiver antenna follows the same rotation that
the transmitter antenna has, it's just that the face each other, so when
you turn one of the 180 degrees such that they face the same direction
you would see that they are in fact rotated in opposite directions.
I'm sure the sat folks can confirm this.
Cheers,
Magnus
I can confirm that I'm 100% sure that the polarization of the two antennas needs
to be the same - i.e. both RHCP or both LHCP. I built two of them for RHCP, and
got appreciate gain.
Despite what other may say, there does seem to be a lot of confusion about this
issue, but I've satisfied myself by building them and testing the gain using a
VNA as the signal source and detector.
Dave
On 07/07/2012 06:21 PM, Dr. David Kirkby wrote:
On 06/ 5/12 12:26 AM, Magnus Danielson wrote:
On 05/06/12 00:30, Dr. David Kirkby wrote:
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.
They would have to have opposite rotation.
The waveform rotation will follow the transmitter antenna into the
receiver antenna. The receiver antenna follows the same rotation that
the transmitter antenna has, it's just that the face each other, so when
you turn one of the 180 degrees such that they face the same direction
you would see that they are in fact rotated in opposite directions.
I'm sure the sat folks can confirm this.
Cheers,
Magnus
I can confirm that I'm 100% sure that the polarization of the two
antennas needs to be the same - i.e. both RHCP or both LHCP. I built two
of them for RHCP, and got appreciate gain.
Despite what other may say, there does seem to be a lot of confusion
about this issue, but I've satisfied myself by building them and testing
the gain using a VNA as the signal source and detector.
We had this straighten out about a month ago, and me posting more or
less as I landed from a transatlantic flight wasn't optimum (tired and
waving hands didn't help, as I got it wrong).
RHCP should match RHCP and LHCP should match LHCP.
Cheers,
Magnus