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Author Topic: circular polarized  (Read 229 times)
KA5ROW
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« on: October 05, 2007, 04:25:24 PM »

Can a circular polarized such as the KLM 435-40CX Antenna  or any polarized antenna for satellite use be used for the purpose of  using the vertical for FM repeaters and then switching to the Horizontal for use on SSB or is there something special about the circular polarized that would not make it suitable for that use.
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AA4PB
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« Reply #1 on: October 05, 2007, 04:40:25 PM »

The antenna is not switchable between vertical and horizontal, its switchable between right-hand and left-hand circular polarization. Using it with a horizontal or vertical is probably better than being cross polarized but not as good as having the correct polarization. You'd be better off to use two separate yagis and switch between them.
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N5EG
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« Reply #2 on: October 05, 2007, 05:44:50 PM »

Yes - a circularly polarized antenna can be used to commmunicate with both vertically and horizontally polarized antennas. There will be a 3 dB loss between a circular antenna and a vertical antenna. Also, a 3 dB loss between a horizontal and a circularly polarized antenna.

  -- Yom, N5EG

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N6AJR
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« Reply #3 on: October 05, 2007, 06:40:49 PM »

or you could remove he switching loop and feed both polorizations directly, but thats a waste of an expensive antenna
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W7AIT
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« Reply #4 on: October 05, 2007, 07:01:16 PM »

See my article in Jan Feb 2007 AMSAT journal, "Hot Rod Arrow".  It is NOT circularly polarized and works well for all 5 satellites I use regularly.  Yes, there is some signal degradation, is a problem NO!  So I compromise and its a good compromise.  Keeps the cost /complexity to a minimum.  And I've had THOUSANDS of Satellite QSO's with that antenna. Also works for earth qso’s without mod….w7ait
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N8EKT
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« Reply #5 on: October 06, 2007, 06:48:29 PM »

Actually right hand circular polarization is the best way to go for both repeaters and base stations.
FM broadcasters discovered decades ago that circular polarity produces much less whip flutter and dead spots with mobile receivers than either fixed polarity.
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WA9SVD
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« Reply #6 on: October 06, 2007, 06:54:33 PM »

The easiest answer is to use the CP antenna "AS-IS," and accept that there will be a (approximately) 3 dB reduction in received signal strength, AND transmitted ERP.  (The 3 dB applies to both transmit and receive.)

    With additional switching/relays (and possibly additional or different phasing lines,) it IS possible to select horizontal OR vertical polarization alone, but the complexity/expense probably isn't worth the effort.  (The method is explained and diagrammed in the ARRL Antenna Book.)
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KE3WD
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« Reply #7 on: October 07, 2007, 09:41:38 PM »

Why worry about a half an S-unit?


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WA3SKN
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« Reply #8 on: October 08, 2007, 06:07:23 AM »

Yes it can be done, with trade-offs.
The real question is whether you are most interested in SSB, FM, or satellite work?
You will probably be better off with multiple antennas.

-Mike.
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