[time-nuts] Antenna question about RHCP/LHCP I'm sure a time-nut can answer

[Rex]

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 Martindale<dave.martindale at 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
>>
>
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