Thanks for clearing up any confusion Magnus, one more question, are the any conditions such as reflected signals that can reverse polarization?
Thomas Knox > Date: Sat, 7 Jul 2012 18:43:10 +0200 > From: mag...@rubidium.dyndns.org > To: time-nuts@febo.com > Subject: Re: [time-nuts] Antenna question about RHCP/LHCP I'm sure a time-nut > can answer > > 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 > > _______________________________________________ > 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. _______________________________________________ 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.