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I'm installing my first beam antenna. I have 2 connection points, one for vertical and 1 for horizontal. So far. I have not found a lot of information which would be better. To run them separately or to build some kind of harness to run them together, which would make it circular. The radio I'm using now only has one antenna connection. I also know that there are switches that make it to run vertical and horizontal together. . I plan to invest in a better radio when I pass my technician's exam. So far. I just talk on 10 and 11 m. I invested in a good antenna rotor. And controller. Any help would be greatly appreciate.. Thank you very much

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    $\begingroup$ hi David, welcome to the site. There’s a lot of background and commentary in your post (good start!), but not an actual question. What is your question? Please be specific so that you can get a helpful answer. $\endgroup$
    – webmarc
    Commented Jan 21 at 14:10
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    $\begingroup$ Some details would be helpful. What frequency band is the antenna built for? What is the intended use (terrestrial?, satellite?). Could you provide more detail on construction (manufacturer, model number, design, ...) $\endgroup$
    – WA9ZZZ
    Commented Jan 21 at 16:16

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Assuming you are using a horiz/vert beam for satellite work..

If you feed vertical and horizontal elements separately, you may need to switch back and forth between them somewhat frequently to get the best signal from a tumbling linear polarized sat, and you will have some loss from a circular polarized sat.

Typically you would harness them together with a phasing harness. This would be a coax jumper that is 1/4 wavelength long, taking into account velocity factor of the coax and any offset between the horizontal and vertical elements. But you'd still want two feeds for this. Feeding from one side of the coax will give you left hand circular, and from the other side right hand circular. Also, feeding both antennas from the same coax will halve the impedance, so this must be adjusted for as well.

The rule of thumb is that transmitting from a horizontal antenna to a vertical antenna is about 7db of loss. Transmitting from a linear antenna to a circular polarized antenna is 3db of loss. Transmitting from a LHCP antenna to a RHCP antenna is 14db of loss, and a linear polarized but tumbling sat (which is typical of amateur satellites) will reverse polarity as it passes over your head....so being able to switch is pretty important.

If you are not using it for satellite work, it might be better to keep them separate so you can switch between vertical work to contact (distant?) repeaters and horizontal work for long distance simplex, presumably SSB.

If you want want to do both, you need a more complex switching set up that probably needs to include switchable impedance matching too.

If rather than a UHF/VHF antenna with separate H/V elements, this is an HF antenna with separate ports to feed the same element, then circular polarization is not an option. If you are trying for skywave, it mostly doesn't matter if you pick horizontal or vertical polarization because faraday rotation will scramble it anyway. (If you do have an HF circular polarized, CP reduces selective fading, but it doesn't matter which direction you pick.) For groundwave, there may be a slight gain or signal to noise ratio advantage to horizontal polarization, but mostly you want to pick the same polarization as the station you are talking to.

Of course, if you are ok with not having the highest possible gain or best signal to noise ratio, you can ignore all that and go with the simpler set up, which is likely to work anyway.

Here is an AMSAT article that exactly covers this issue: https://www.amsat.org/amsat/articles/i8cvs/Part_1_AMSATJournal_MarApr07_I8CVS_Polarization-1.pdf

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    $\begingroup$ Very surprised that circular polarization switches as the satellite passes over! Could you elaborate on how that happens? And why does it not happen for GPS? $\endgroup$ Commented Jan 22 at 7:12
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    $\begingroup$ But even if we didn't, there's literally no relationship between frequency shifts and change in polarization. $\endgroup$ Commented Jan 23 at 2:13
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    $\begingroup$ Yes, linear satellites will change the orientation of their polarisation as they pass. LEO satellites fly more like aircraft, nothing relativistic about that. GPS satellites are so high (3 earth radii) they're basically always facing down. GPS polarisation is always RHCP. But by the time it reaches your wristwatch on a city street, it could be anything, so Nordic is saying that a linear antenna is just as good as a circular patch, fair enough. Not much to do with an amateur circular pol satellite beam antenna though. $\endgroup$
    – tomnexus
    Commented Jan 24 at 1:03
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    $\begingroup$ @user10489 sadly you're really wrong, it's not even remotely clear why you think that the need for time adjustment means the polarization changes. There's simply no causal link here! Circular polarization doesn't change due to Doppler, whether you need to take relativistic effects into account or not (and you don't, here. The context "wave propagation" is not the same as "long term distributed oscillators in space", sorry) $\endgroup$ Commented Jan 24 at 2:09
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    $\begingroup$ We're rambling about polarisation, and this answer has several misconceptions. Maybe start here: en.m.wikipedia.org/wiki/Polarization_(waves)#Antennas and here vu2nsb.com/amateur-satellite-radio/satellite-communications . Doppler frequency shift is something else; you can hear it on a fire engine, no need for GPS or relativity. Finally, none of this answers OP's (non-)question, for all we know it's an HF quad beam with two feedpoint options. $\endgroup$
    – tomnexus
    Commented Jan 24 at 2:14

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