[Elecraft] [K3] CP antenna article in Dec QST
My 144-MHz dual-polarity diversity receiver is exactly what you describe, only for HF in your case: two orthogonal antennas, each fed to one of the K3 receivers. In my case a dual-channel 144-MHz Rx converter is feeding 28-MHz to the K3 and fed by my X-yagis. To observe the polarity effects the two separate receiver audio streams are fed to a a computer which runs Linrad, a program for weak-signal reception that also resolves the polarity angle from the two orthogonal signals. http://www.kl7uw.com/eme144.htm http://g7rau.demon.co.uk/sm5bsz/index.htm No fancy coax network is needed; just make the baluns and feedlines identical. 73, Ed BTW Eric is a member of the ARRL 600m Experimental Group: WD2XSH. -- Message: 8 Date: Fri, 12 Nov 2010 19:31:56 - From: Bill VanAlstyne W5WVO w5...@cybermesa.net Subject: Re: [Elecraft] [K3] CP antenna article in Dec QST [was: Education please] To: Elecraft Reflector elecraft@mailman.qth.net Message-ID: 6720a8423c184619a1be732734b53...@billhp9250 Content-Type: text/plain; format=flowed; charset=iso-8859-1; reply-type=original Just as a heads-up for anyone interested in this subject -- in the December QST just now arriving in subscribers' hands, there is a cool article on X-O circular polarization (CP) antennas. The author (Eric Nichols, KL7AJ) discusses the fact that all F-layer ionospheric propagation is actually circular and arrives at the receiving antenna by way of one of two different refraction paths, depending on... well, you can read the article for the theoretical details. He says all of this has actually been well understood in physics and radio engineering circles since the 1930s, but (with a few exceptions) has had scant mention in the ham radio literature. The executive summary is that you can build a receive antenna (which empirically demonstrates and proves the theory) consisting of two inverted vee antennas constructed around a central support, with the four legs arranged accurately such that the slopes of the legs are all identical, the angles between the legs are all 90 degrees, and the two feedlines (connected through identical baluns) are precisely the same length. By then inserting a 1/4-wavelength (90 degree) delay line in one dipole's feedline and then adding the signals together through a T or some more sophisticated combiner, you will get either a large increase in signal strength with respect to either dipole individually, OR a commensurately large loss of signal strength with respect to either dipole individually -- depending on which variety of circular polarization (X-wave or O-wave) you are getting from the station being received at the moment. This is one kind of orthogonal receiving antenna that could have very practical uses on the HF bands, especially if you have a diversity-capable receiver such as the K3. One possibility I can think of: You could set up two separate X-O inverted vee antenna systems on two separated support masts, each magnetically aligned as described in the article, with one antenna set up for X waves and the other set up for O waves. Connect the X-wave configured antenna to one receiver, the O-wave configured antenna to the other receiver. And say goodbye to a lot of the QSB normally associated with F-layer-propagated reception! (At least it seems to me that it would have that effect.) Another possibility: use ultra-fast PIN diode switching of the 90-degree delay line and reconstruct both an X and O output from a single antenna. Since even PIN diodes probably can't switch faster than, say, one cycle at 14 MHz (about 72 nanoseconds), I don't know if this would work, as you would be switching multiple cycles and fractions of cycles (asynchronously) back and forth... Would this matter? You would end up with a 3-dB loss on each leg, but that in itself should be trivial; absolute sensitivity is not an issue at HF. But would the chopped-up waves be properly demodulated in the receivers? This is about where the engineering of it goes over my head... Comments? Bill W5WVO 73, Ed - KL7UW, WD2XSH/45 == BP40IQ 500 KHz - 10-GHz www.kl7uw.com EME: 144-800*w, 432-100w, 1296-testing*, 3400-winter? DUBUS Magazine USA Rep dubus...@hotmail.com == *temp not in service __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] [K3] CP antenna article in Dec QST [was: Education please]
Just as a heads-up for anyone interested in this subject -- in the December QST just now arriving in subscribers' hands, there is a cool article on X-O circular polarization (CP) antennas. The author (Eric Nichols, KL7AJ) discusses the fact that all F-layer ionospheric propagation is actually circular and arrives at the receiving antenna by way of one of two different refraction paths, depending on... well, you can read the article for the theoretical details. He says all of this has actually been well understood in physics and radio engineering circles since the 1930s, but (with a few exceptions) has had scant mention in the ham radio literature. The executive summary is that you can build a receive antenna (which empirically demonstrates and proves the theory) consisting of two inverted vee antennas constructed around a central support, with the four legs arranged accurately such that the slopes of the legs are all identical, the angles between the legs are all 90 degrees, and the two feedlines (connected through identical baluns) are precisely the same length. By then inserting a 1/4-wavelength (90 degree) delay line in one dipole's feedline and then adding the signals together through a T or some more sophisticated combiner, you will get either a large increase in signal strength with respect to either dipole individually, OR a commensurately large loss of signal strength with respect to either dipole individually -- depending on which variety of circular polarization (X-wave or O-wave) you are getting from the station being received at the moment. This is one kind of orthogonal receiving antenna that could have very practical uses on the HF bands, especially if you have a diversity-capable receiver such as the K3. One possibility I can think of: You could set up two separate X-O inverted vee antenna systems on two separated support masts, each magnetically aligned as described in the article, with one antenna set up for X waves and the other set up for O waves. Connect the X-wave configured antenna to one receiver, the O-wave configured antenna to the other receiver. And say goodbye to a lot of the QSB normally associated with F-layer-propagated reception! (At least it seems to me that it would have that effect.) Another possibility: use ultra-fast PIN diode switching of the 90-degree delay line and reconstruct both an X and O output from a single antenna. Since even PIN diodes probably can't switch faster than, say, one cycle at 14 MHz (about 72 nanoseconds), I don't know if this would work, as you would be switching multiple cycles and fractions of cycles (asynchronously) back and forth... Would this matter? You would end up with a 3-dB loss on each leg, but that in itself should be trivial; absolute sensitivity is not an issue at HF. But would the chopped-up waves be properly demodulated in the receivers? This is about where the engineering of it goes over my head... Comments? Bill W5WVO -Original Message- From: Ken Alexander Sent: Friday, November 12, 2010 15:16 To: Elecraft Reflector ; Lee Buller Subject: Re: [Elecraft] Education please OK, I guess the ham application for an orthogonal antenna would be to use two loops at 90 degrees to each other. With the electronic trickery I mentioned below you would have yourself a dandy direction finding antenna. Great for transmitter hunts and tracking down jammers and other bad guys. 73 - Ken --- On Fri, 11/12/10, Ken Alexander k.alexan...@rogers.com wrote: From: Ken Alexander k.alexan...@rogers.com Subject: Re: [Elecraft] Education please To: Elecraft Reflector elecraft@mailman.qth.net, Lee Buller k...@swbell.net Date: Friday, November 12, 2010, 10:04 AM This is subject to much correction from people who are smarter than me, but my oversimplified description is that an orthogonal antenna basically consists of three loop antennas oriented in three planes that are at right angles to each other (X, Y and Z axes if you remember your basic geometry). The antenna are bidirectional in each of those planes. With some associated electronic wizardry, you can compare the signals received by each antenna and establish the direction (in three-dimensional space) of a given transmitter. Sort of a method of electronic triangulation. I don't know how much application it has in ham radio. I don't recall seeing any ham call signs associated with the documents I read during my Google search! It looks like most of the uses are industrial. Hope that gets you started, and like I said, probably subject to some clarification by brainier people. 73, Ken Alexander VE3HLS --- On Fri, 11/12/10, Lee Buller k...@swbell.net wrote: From: Lee Buller k...@swbell.net Subject: [Elecraft] Education please To: Elecraft Reflector elecraft@mailman.qth.net Date: Friday, November 12, 2010, 9:32 AM What the heck is a orthogonal antenna? Would someone define it or give an example? I have Googled it but it is
Re: [Elecraft] [K3] CP antenna article in Dec QST [was: Education please]
We used most of this at N4A this summer, see my other post for details. Actually converting this to circular polarization at the RX end is self-defeating because the rotation of polarization is itself rotating, not at all steady. If listening to the two antennas separately in diversity, one is always doing fine when the other tanks. This means copying the first time through, rather than asking for repeats. Listening to the circular polarization would have the same number of fades as listening with a single dipole, once every rotation of rotation. The noise floor exhibited the same degree and kind of rotation. This was pretty clear listening to the weaker EU signals. The stronger signals did NOT exhibit this rotation, or nearly to the same degree, and stayed in the same side of the diversity RX, leading to the speculation that the rotation was more present on stations without the ability to transmit at low angles, or some such. Completely unable to prove such a conjecture of course. 73, Guy. On Fri, Nov 12, 2010 at 2:31 PM, Bill VanAlstyne W5WVO w5...@cybermesa.net wrote: Just as a heads-up for anyone interested in this subject -- in the December QST just now arriving in subscribers' hands, there is a cool article on X-O circular polarization (CP) antennas. The author (Eric Nichols, KL7AJ) discusses the fact that all F-layer ionospheric propagation is actually circular and arrives at the receiving antenna by way of one of two different refraction paths, depending on... well, you can read the article for the theoretical details. He says all of this has actually been well understood in physics and radio engineering circles since the 1930s, but (with a few exceptions) has had scant mention in the ham radio literature. The executive summary is that you can build a receive antenna (which empirically demonstrates and proves the theory) consisting of two inverted vee antennas constructed around a central support, with the four legs arranged accurately such that the slopes of the legs are all identical, the angles between the legs are all 90 degrees, and the two feedlines (connected through identical baluns) are precisely the same length. By then inserting a 1/4-wavelength (90 degree) delay line in one dipole's feedline and then adding the signals together through a T or some more sophisticated combiner, you will get either a large increase in signal strength with respect to either dipole individually, OR a commensurately large loss of signal strength with respect to either dipole individually -- depending on which variety of circular polarization (X-wave or O-wave) you are getting from the station being received at the moment. This is one kind of orthogonal receiving antenna that could have very practical uses on the HF bands, especially if you have a diversity-capable receiver such as the K3. One possibility I can think of: You could set up two separate X-O inverted vee antenna systems on two separated support masts, each magnetically aligned as described in the article, with one antenna set up for X waves and the other set up for O waves. Connect the X-wave configured antenna to one receiver, the O-wave configured antenna to the other receiver. And say goodbye to a lot of the QSB normally associated with F-layer-propagated reception! (At least it seems to me that it would have that effect.) Another possibility: use ultra-fast PIN diode switching of the 90-degree delay line and reconstruct both an X and O output from a single antenna. Since even PIN diodes probably can't switch faster than, say, one cycle at 14 MHz (about 72 nanoseconds), I don't know if this would work, as you would be switching multiple cycles and fractions of cycles (asynchronously) back and forth... Would this matter? You would end up with a 3-dB loss on each leg, but that in itself should be trivial; absolute sensitivity is not an issue at HF. But would the chopped-up waves be properly demodulated in the receivers? This is about where the engineering of it goes over my head... Comments? Bill W5WVO -Original Message- From: Ken Alexander Sent: Friday, November 12, 2010 15:16 To: Elecraft Reflector ; Lee Buller Subject: Re: [Elecraft] Education please OK, I guess the ham application for an orthogonal antenna would be to use two loops at 90 degrees to each other. With the electronic trickery I mentioned below you would have yourself a dandy direction finding antenna. Great for transmitter hunts and tracking down jammers and other bad guys. 73 - Ken --- On Fri, 11/12/10, Ken Alexander k.alexan...@rogers.com wrote: From: Ken Alexander k.alexan...@rogers.com Subject: Re: [Elecraft] Education please To: Elecraft Reflector elecraft@mailman.qth.net, Lee Buller k...@swbell.net Date: Friday, November 12, 2010, 10:04 AM This is subject to much correction from people who are smarter than me, but my oversimplified description is that an orthogonal antenna
