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

Max Robinson max at maxsmusicplace.com
Mon Jun 4 21:18:29 EDT 2012


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: max at maxsmusicplace.com

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----- Original Message ----- 
From: "Dr. David Kirkby" <david.kirkby at onetel.net>
To: "Discussion of precise time and frequency measurement" 
<time-nuts at 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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