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Author Topic: 2 Meter Helical Antenna (Circular Polarized)  (Read 2743 times)
AB2UI
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Posts: 9




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« on: March 10, 2006, 06:23:11 PM »

I'm looking to build or buy a 2 meter circular polarized antenna for use as a satellite uplink antenna.  Currently using a 4 element yagi, but I am getting some spin fade since the yagi is vertical polarized.  Anyone have any links to articles on the above?

Thanks and 73's

Adam
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KB1LKR
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Posts: 1899




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« Reply #1 on: March 11, 2006, 06:57:08 AM »

A search of ARRL finds: Jan 1990 QST "Circularly Polarized Quagi Antennas for Space Communications", Gene Marcus W3PM/GM4YRE

Also L. B, Cebik (W4RNL)'s  site, particularly: "Notes on Axial-Mode Helical Antennas in Amateur Service" http://www.cebik.com/vhf/gh1.html
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WA9SVD
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Posts: 2201




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« Reply #2 on: March 15, 2006, 07:23:09 AM »

One other way would be to use another, identical yagi and use cable phasing lines to achieve CP.  Although you can mount them one horizontal and one vertical, you would need a cross-boom to provide the proper spacing.  But usually, in such an installation, the two antennas are mounted at 45� angles to the horizontal, so they are in an "X" pattern, not a " + " pattern.  The disadvantage uf using CP in this configuration is that you lose approx 3dB due to the fact that you are splitting the power between two antennas.
    You can build the necessary wiring harness yourself, or you can purchase ready made harnesses from some of the satellite antenna manufacturers.  The ARRL has several books that can provide the "nuts and bolts" procedure for such a system; so does the RSGB VHF/UHF manual, also available from the ARRL.  With proper switching, it has the advantage that you can choose between left and right CP, which you can't do with a helix.
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KE4DRN
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Posts: 3721




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« Reply #3 on: March 16, 2006, 06:51:30 PM »

hi adam,

here is a link for a turnstile sat antenna

http://www.cebik.com/vhf/ms2.html

73 james
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KB1GMX
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Posts: 760




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« Reply #4 on: April 06, 2006, 07:16:22 PM »

Go to http://www.clarc.org/Articles/uhf.htm

Copy one of the VHF antennas and follow his suggestion to build two on one boom and make a phasing harness.

I did this at UHF and it's very good, and cheap.

Allison
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