I had an idea pop in my head for a simple turnstile antenna, and am not finding much info on what I want to do via Google searches I wanted to bounce this off the list and see what people think.
My idea consists of three main points:
-Antenna elements being conventional (non-folded) inverted V dipoles, tuning the length for resonance and angle to set at 50 ohms each -1/4 wave 50 ohm phasing line between the sets of dipoles -Feed via DK7ZB match using a 1/4 wave paralleled 2x75 ohm line section (37 ohms), transforming the 25 ohms back up to right around 50 ohms for final feed
This approach would give the following advantages:
-Lower SWR than standard 75-ohm parallel turnstiles -Dipoles could be individually tuned via direct 50 ohm feed during construction -DK7ZB match is constructed out of inexpensive 75-ohm coax -Phasing line length would only affect phase, instead of phase and impedance.
My main question, though is: With dipole elements canted down roughly 35 degrees from vertical (what I'm ballparking to get them down to 50 ohms), am I going to see noticeably degraded performance, especially regarding the polarization?
Thanks for any tips or discussion!
--Matt KC4YLV
Hi Matt,
are you referring to a turnstile antenna like the one available from WIMO here in Germany ?
Please see the following link: http://www.wimo.de/download/ta1.pdf
Best regards
Matthias
www.dd1us.de
-----Ursprüngliche Nachricht----- Von: [email protected] [mailto:[email protected]] Im Auftrag von Jonny 290 Gesendet: Freitag, 28. Februar 2014 20:50 An: [email protected] Betreff: [amsat-bb] Inverted-V turnstile idea
I had an idea pop in my head for a simple turnstile antenna, and am not finding much info on what I want to do via Google searches I wanted to bounce this off the list and see what people think.
My idea consists of three main points:
-Antenna elements being conventional (non-folded) inverted V dipoles, tuning the length for resonance and angle to set at 50 ohms each -1/4 wave 50 ohm phasing line between the sets of dipoles -Feed via DK7ZB match using a 1/4 wave paralleled 2x75 ohm line section (37 ohms), transforming the 25 ohms back up to right around 50 ohms for final feed
This approach would give the following advantages:
-Lower SWR than standard 75-ohm parallel turnstiles -Dipoles could be individually tuned via direct 50 ohm feed during construction -DK7ZB match is constructed out of inexpensive 75-ohm coax -Phasing line length would only affect phase, instead of phase and impedance.
My main question, though is: With dipole elements canted down roughly 35 degrees from vertical (what I'm ballparking to get them down to 50 ohms), am I going to see noticeably degraded performance, especially regarding the polarization?
Thanks for any tips or discussion!
--Matt KC4YLV _______________________________________________ Sent via [email protected]. 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
I have 2 of the ELK antennas which I mount at 90 degree angle to each other and switch between as the satellite rotates. My question is:
Could I feed the two ELK antennas which are 4 feet apart, on the same boom and at right angles to each other, in quadrature phase and achieve circular polarization or perhaps decent elliptical polarization?
Thanks,
Doug K9DLP
Yes, it can be done. The "Satellite Experimenters Handbook" describes it. I have done it with Arrow antennas.
Here are a couple pictures from our 2005 setup: http://www.w0wtn.org/img_browse.php?i=/images/field_day_2005/p0000016.jpg http://www.w0wtn.org/img_browse.php?i=/images/field_day_2005/KK0SD_Sat_Ant.j pg http://www.w0wtn.org/img_browse.php?i=/images/field_day_2005/p0000017.jpg
It worked very well.
73, Joe kk0sd
-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Douglas Phelps Sent: Friday, February 28, 2014 3:14 PM To: [email protected] Subject: [amsat-bb] circular polarization of antennas not on same axis
I have 2 of the ELK antennas which I mount at 90 degree angle to each other and switch between as the satellite rotates. My question is:
Could I feed the two ELK antennas which are 4 feet apart, on the same boom and at right angles to each other, in quadrature phase and achieve circular polarization or perhaps decent elliptical polarization?
Thanks,
Doug K9DLP _______________________________________________ Sent via [email protected]. 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
Yes, that's exactly what I had in mind! So it very well may be a viable design, then.
-- Matt
-jonny 290
On Fri, Feb 28, 2014 at 2:51 PM, Matthias Bopp [email protected] wrote:
Hi Matt,
are you referring to a turnstile antenna like the one available from WIMO here in Germany ?
Please see the following link: http://www.wimo.de/download/ta1.pdf
Best regards
Matthias
www.dd1us.de
-----Ursprüngliche Nachricht----- Von: [email protected] [mailto:[email protected]] Im Auftrag von Jonny 290 Gesendet: Freitag, 28. Februar 2014 20:50 An: [email protected] Betreff: [amsat-bb] Inverted-V turnstile idea
I had an idea pop in my head for a simple turnstile antenna, and am not finding much info on what I want to do via Google searches I wanted to bounce this off the list and see what people think.
My idea consists of three main points:
-Antenna elements being conventional (non-folded) inverted V dipoles, tuning the length for resonance and angle to set at 50 ohms each -1/4 wave 50 ohm phasing line between the sets of dipoles -Feed via DK7ZB match using a 1/4 wave paralleled 2x75 ohm line section (37 ohms), transforming the 25 ohms back up to right around 50 ohms for final feed
This approach would give the following advantages:
-Lower SWR than standard 75-ohm parallel turnstiles -Dipoles could be individually tuned via direct 50 ohm feed during construction -DK7ZB match is constructed out of inexpensive 75-ohm coax -Phasing line length would only affect phase, instead of phase and impedance.
My main question, though is: With dipole elements canted down roughly 35 degrees from vertical (what I'm ballparking to get them down to 50 ohms), am I going to see noticeably degraded performance, especially regarding the polarization?
Thanks for any tips or discussion!
--Matt KC4YLV _______________________________________________ Sent via [email protected]. 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
participants (4)
-
Douglas Phelps -
Gary "Joe" Mayfield -
Jonny 290 -
Matthias Bopp