I heard Arecibo would be using circular polarization, but I haven't heard if it will be left or right-handed circular polarization.
I also heard that there's a way to do circular polarization with the popular "cheap yagis." Apparently the details are in an article in the April 1999 issue of CQ VHF "Cheap Circular Polarization? It Can Be Done" on pages 66-69.
Is there anyone on the list that has this back issue that can tell me what the method is that is described in this article? Is it a physical quarter-wave displacement on the same boom? Two booms with a quarter-wave coax delay? Something else? How is the circular polarization done with the cheap yagis?
Douglas KA2UPW/5
At 12:16 PM 4/15/2010, Douglas Quagliana wrote:
I heard Arecibo would be using circular polarization, but I haven't heard if it will be left or right-handed circular polarization.
I also heard that there's a way to do circular polarization with the popular "cheap yagis." Apparently the details are in an article in the April 1999 issue of CQ VHF "Cheap Circular Polarization? It Can Be Done" on pages 66-69.
Is there anyone on the list that has this back issue that can tell me what the method is that is described in this article? Is it a physical quarter-wave displacement on the same boom? Two booms with a quarter-wave coax delay? Something else? How is the circular polarization done with the cheap yagis?
Douglas KA2UPW/5
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
You are running out of time to build a CP antenna system for the Arecibo eme event, aren't you? I would not worry about it and just use a simple yagi in any polarity. Yes, you will lose 3-dB of the signal from Arecibo, but it probably won't matter much if your antenna is big enough. Arecibo will be transmitting an effective power of 441 Mw.
But if you want to make a CP antenna from a yagi, you need two sets of elements perpendicular to each other (i.e. two antennas mounted on a single boom or two separate antennas one rotated 90-degrees in polarity from the other. If both are mounted so the antennas are in-phase you need to split the feedline and add 1/4 wavelength of cable to one antenna. Or you can split the feedline equally if one antenna is spaced 1/4 wavelength ahead of the other. The relation of the fed elements determine whether you get RH or LH CP. The center conductor is connected to one side of the fed element (this is called the + side). If the antenna to the rear (or not with extra feedline) is vertical with "+" straight up and the other antenna has its "+" element pointing to the right, you get RHCP. Reverse it and you get LHCP. For antennas in the "X" configuration (back antenna "+" up and to the left, front antenna "=" up and to the right for RHCP.
Caveat: I f you have the antenna configured backwards for Arecibo then you will hear nothing. Little understood fact of eme: RHCP signals are reflected by the Moon as LHCP signals back to earth, and vice versa. We have no info on Arecibo, but for hams the convention is to Tx - RHCP and RX - LHCP for eme. So if you build a CP antenna and you plan to transmit, also, you will need a polarity switching system between Tx and Rx.
I am building a simple two-element Quagi (linear pol) to feed my dish (24.5 dBi). VK3UM spreadsheet says Arecibo will hear me with a +20 dB signal on SSB.
73, Ed - KL7UW, WD2XSH/45 ====================================== BP40IQ 500 KHz - 10-GHz www.kl7uw.com EME: 144-600w, 432-100w, 1296-60w, 3400-fall 2010 DUBUS Magazine USA Rep dubususa@hotmail.com ======================================
----- Original Message ----- From: "Edward Cole" kl7uw@acsalaska.net To: "Douglas Quagliana" dquagliana@aol.com; "amsat" amsat-bb@amsat.org Sent: Thursday, April 15, 2010 11:49 PM Subject: [amsat-bb] Re: Arecibo and circular polarization using cheap yagis
Or you can split the feedline equally if one antenna is spaced 1/4 wavelength ahead of the other. The relation of the fed elements determine whether you get RH or LH CP. The center conductor is connected to one side of the fed element (this is called the + side). If the antenna to the rear (or not with extra feedline) is vertical with "+" straight up and the other antenna has its "+" element pointing to the right, you get RHCP. Reverse it and you get LHCP.
73, Ed - KL7UW, WD2XSH/45
Hi Ed, KL7UW
Please find here a necessary amendment to your statement:
We assume that you are looking from the rear of the antenna in direction of propagation and one antenna is spaced 1/4 wavelenght ahead of the other.
If the dipole of the rear antenna is vertical with "+" straight up and if the dipole of the front antenna is horizontal and has its "+" element pointing to the left then you get RHCP. Reverse it and you get LHCP
In a separate email I have sent to you a drawing showing how two linearly polarized components shifted 90° one to the other adds togheter to generate a circularly polarized wave but I can send the same drawing to everybody need it.
For antennas in the "X" configuration (back antenna "+" up and to the left, front antenna "=" up and to the right for RHCP.
If the signe "=" is a typing mistake and you means " - " (minus) then your statement is correct.
73" de
i8CVS Domenico
Hi All,
A picture is worth a thousand words.........
http://sv1bsx.50webs.com/antenna-pol/polarization.html
Maybe this will help......
73, Rick WA4NVM
Subject: [amsat-bb] Re: Arecibo and circular polarization using cheap yagis
Or you can split the feedline equally if one antenna is spaced 1/4 wavelength ahead of the other. The relation of the fed elements determine whether you get RH or LH CP. The center conductor is connected to one side of the fed element (this is called the + side). If the antenna to the rear (or not with extra feedline) is vertical with "+" straight up and the other antenna has its "+" element pointing to the right, you get RHCP. Reverse it and you get LHCP.
73, Ed - KL7UW, WD2XSH/45
Hi Ed, KL7UW
Please find here a necessary amendment to your statement:
We assume that you are looking from the rear of the antenna in direction of propagation and one antenna is spaced 1/4 wavelenght ahead of the other.
If the dipole of the rear antenna is vertical with "+" straight up and if the dipole of the front antenna is horizontal and has its "+" element pointing to the left then you get RHCP. Reverse it and you get LHCP
In a separate email I have sent to you a drawing showing how two linearly polarized components shifted 90° one to the other adds togheter to generate a circularly polarized wave but I can send the same drawing to everybody need it.
For antennas in the "X" configuration (back antenna "+" up and to the left, front antenna "=" up and to the right for RHCP.
If the signe "=" is a typing mistake and you means " - " (minus) then your statement is correct.
73" de
i8CVS Domenico
_______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
At 11:25 AM 4/16/2010 -0500, you wrote:
Hi All,
A picture is worth a thousand words.........
http://sv1bsx.50webs.com/antenna-pol/polarization.html
Maybe this will help......
73, Rick WA4NVM
Rick,
Thank you for this! Book-marked! When I get the chance to do the much needed maintenance on my system, I may build new phasing harnesses now.
73, KB7ADL
At 08:25 AM 4/16/2010, Rick - WA4NVM wrote:
Hi All,
A picture is worth a thousand words.........
http://sv1bsx.50webs.com/antenna-pol/polarization.html
Maybe this will help......
73, Rick WA4NVM
Subject: [amsat-bb] Re: Arecibo and circular polarization using cheap yagis
Or you can split the feedline equally if one antenna is spaced 1/4 wavelength ahead of the other. The relation of the fed elements determine whether you get RH or LH CP. The center conductor is connected to one side of the fed element (this is called the + side). If the antenna to the rear (or not with extra feedline) is vertical with "+" straight up and the other antenna has its "+" element pointing to the right, you get RHCP. Reverse it and you get LHCP.
73, Ed - KL7UW, WD2XSH/45
Hi Ed, KL7UW
Please find here a necessary amendment to your statement:
We assume that you are looking from the rear of the antenna in direction of propagation and one antenna is spaced 1/4 wavelenght ahead of the other.
If the dipole of the rear antenna is vertical with "+" straight up and if the dipole of the front antenna is horizontal and has its "+" element pointing to the left then you get RHCP. Reverse it and you get LHCP
In a separate email I have sent to you a drawing showing how two linearly polarized components shifted 90° one to the other adds togheter to generate a circularly polarized wave but I can send the same drawing to everybody need it.
For antennas in the "X" configuration (back antenna "+" up and to the left, front antenna "=" up and to the right for RHCP.
If the signe "=" is a typing mistake and you means " - " (minus) then your statement is correct.
73" de
i8CVS Domenico
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
OK, that seems counterintuitive, but I guess I was not accounting for both driven elements to be fed in-phase. The electrical vector must rotate clockwise to produce RHCP, and so it does in Domenico's drawing. Dom's drawing actually shows the rear driven element horizontal and the forward driven element vertical, but its the relationship that produces the rotation so does not matter (i.e. they both could be angled +45 and -45 degrees in the "X" configuration). I guess my confusion was not accounting for both elements being driven in-phase.
My M2 436CP42 looks just like Dom's drawing but it has a 1/2 wavelength longer phasing line between the rear and front driven elements. They say this is the setup for RHCP? It would seem the M2 system would have the front antenna 180-degrees out of phase? So would that not produce LHCP? It is actually easier to visualize with both elements at the same point on the boom and one fed with a 1/4 wave longer feed line.
Nice thing about helical antennas is the corkscrew turns in the direction of the rotating wave.
73, Ed - KL7UW, WD2XSH/45 ====================================== BP40IQ 500 KHz - 10-GHz www.kl7uw.com EME: 144-600w, 432-100w, 1296-60w, 3400-fall 2010 DUBUS Magazine USA Rep dubususa@hotmail.com ======================================
----- Original Message ----- From: "Edward Cole" kl7uw@acsalaska.net To: "Rick - WA4NVM" wa4nvm@comcast.net; "i8cvs" domenico.i8cvs@tin.it; "Douglas Quagliana" dquagliana@aol.com; "amsat" amsat-bb@amsat.org Sent: Friday, April 16, 2010 8:20 PM Subject: Re: [amsat-bb] Re: Arecibo and circular polarization using cheap yagis
My M2 436CP42 looks just like Dom's drawing but it has a 1/2 wavelength longer phasing line between the rear and front driven elements. They say this is the setup for RHCP? It would seem the M2 system would have the front antenna 180-degrees out of phase? So would that not produce LHCP? It is actually easier to visualize with both elements at the same point on the boom and one fed with a 1/4 wave longer feed line.
73, Ed - KL7UW, WD2XSH/45
Hi Ed, KL7UW
What the M2 say is correct.
In a crossed yagi with vertical and horizontal elements spaced 1/4 wavelenght ( 90°) over the boom if you look from the rear of the antenna toward the direction of radiation the phase relations are as follows:
Assume that the power is splitted in two equal parts and the horizontal and vertical dipoles are feed in phase with equal lenghts of coax cable.
The inner conductor (+) of one coax cable is connected to the right side of the horizontal rear dipole. The inner conductor (+) of the other coax cable is connected to the upper side of the front vertical dipole.
With the above coax cable connections and +90° of phase shift over the boom the antenna radiates RHCP
If you now add a 1/2 electrical wavelenght (180°) to the coax cable supplying the front dipole then the polarization reverses in LHCP because 90° of mechanical shift over the boom minus 180° for the 1/2 wavelength of coax cable make a difference of - 90°
This is exactly what your M2 436CP42 does when switching between RHCP to LHCP
I agree with you that it is actually easier to visualize with both elements at the same point on the boom and one fed with a 1/4 wave longer feed line.
73" de
i8CVS Domenico
But what about antennas like the M2 ants where it's a balanced feed, and there is no + side of the element or coax?
The Original Rolling Ball Clock Idle Tyme Idle-Tyme.com http://www.idle-tyme.com
On 4/16/2010 9:37 PM, i8cvs wrote:
----- Original Message ----- From: "Edward Cole"kl7uw@acsalaska.net To: "Rick - WA4NVM"wa4nvm@comcast.net; "i8cvs"domenico.i8cvs@tin.it; "Douglas Quagliana"dquagliana@aol.com; "amsat"amsat-bb@amsat.org Sent: Friday, April 16, 2010 8:20 PM Subject: Re: [amsat-bb] Re: Arecibo and circular polarization using cheap yagis
My M2 436CP42 looks just like Dom's drawing but it has a 1/2 wavelength longer phasing line between the rear and front driven elements. They say this is the setup for RHCP? It would seem the M2 system would have the front antenna 180-degrees out of phase? So would that not produce LHCP? It is actually easier to visualize with both elements at the same point on the boom and one fed with a 1/4 wave longer feed line.
73, Ed - KL7UW, WD2XSH/45
Hi Ed, KL7UW
What the M2 say is correct.
In a crossed yagi with vertical and horizontal elements spaced 1/4 wavelenght ( 90°) over the boom if you look from the rear of the antenna toward the direction of radiation the phase relations are as follows:
Assume that the power is splitted in two equal parts and the horizontal and vertical dipoles are feed in phase with equal lenghts of coax cable.
The inner conductor (+) of one coax cable is connected to the right side of the horizontal rear dipole. The inner conductor (+) of the other coax cable is connected to the upper side of the front vertical dipole.
With the above coax cable connections and +90° of phase shift over the boom the antenna radiates RHCP
If you now add a 1/2 electrical wavelenght (180°) to the coax cable supplying the front dipole then the polarization reverses in LHCP because 90° of mechanical shift over the boom minus 180° for the 1/2 wavelength of coax cable make a difference of - 90°
This is exactly what your M2 436CP42 does when switching between RHCP to LHCP
I agree with you that it is actually easier to visualize with both elements at the same point on the boom and one fed with a 1/4 wave longer feed line.
73" de
i8CVS Domenico
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
----- Original Message ----- From: "Idle-Tyme" nss@mwt.net To: amsat-bb@amsat.org Sent: Saturday, April 17, 2010 4:51 AM Subject: [amsat-bb] Re: Arecibo and circular polarization using cheap yagis
But what about antennas like the M2 ants where it's a balanced feed, and there is no + side of the element or coax?
The Original Rolling Ball Clock Idle Tyme Idle-Tyme.com http://www.idle-tyme.com
Hi Idle-Tyme
The M2 antennas uses folded dipoles wich is a balanced system with impedance of 200 ohm.
In order to transform the impedance from 200 to 50 ohm and change from a balanced system (the folded dipole) to a unbalanced system (the 50 ohm feed line) a 1/2 electrical wavelenght of 50 ohm coax cable called balun is connected with the inner conductors across the dipole studs.
the braids of the 1/2 electrical wavelenght coax balun are soldered togheter with the braid of the 50 ohm coax feed line and grounded to the center of the antenna boom.
The side of the folded dipole connected to the inner conductor of the feed line is the (+) side of the element.
I hope this helps
73" de
i8CVS Domenico
Hi Rick, WA4NVM
Plese look at the two last drawing of the SV1BSX page:
http://sv1bsx.50webs.com/antenna-pol/polarization.html
You will see that the polarity marked (+) over the dipoles are correct for both the clockwice CW or RHCP polarization as well for the counterclockwise CCW or LHCP polarization.
By the way the drawings of the circular pats of the wave along the antennas are wrong and must be inverted. The green path on the top picture is LHCP and must be inverted with the red path in the bottom picture wich is RHCP
Sorry I can't informe my very good friend Mak SV1BSX because unfortunately the last year he went SK but he did a very beautiful job.
73" de
i8CVS Domenico
----- Original Message ----- From: "Rick - WA4NVM" wa4nvm@comcast.net To: "i8cvs" domenico.i8cvs@tin.it; "Douglas Quagliana" dquagliana@aol.com; "amsat" amsat-bb@amsat.org; "Edward Cole" kl7uw@acsalaska.net Sent: Friday, April 16, 2010 6:25 PM Subject: Re: [amsat-bb] Re: Arecibo and circular polarization using cheap yagis
Hi All,
A picture is worth a thousand words.........
http://sv1bsx.50webs.com/antenna-pol/polarization.html
Maybe this will help......
73, Rick WA4NVM
Hi Rick, WA4NVM
Plese look at the two last drawing of the SV1BSX page:
http://sv1bsx.50webs.com/antenna-pol/polarization.html
You will see that the polarity marked (+) over the dipoles are correct for both the clockwice CW or RHCP polarization as well for the counterclockwise CCW or LHCP polarization.
By the way the drawings of the circular pats of the wave along the antennas are wrong and must be inverted. The green path on the top picture is LHCP and must be inverted with the red path in the bottom picture wich is RHCP
Sorry I can't informe my very good friend Mak SV1BSX because unfortunately the last year he went SK but he did a very beautiful job.
73" de
i8CVS Domenico
participants (6)
-
Douglas Quagliana -
Edward Cole -
i8cvs -
Idle-Tyme -
Rick - WA4NVM -
Vince Fiscus, KB7ADL