Linear vs circular polarization - Comparison video

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Linear vs circular polarization - Comparison video

Postby Mark Hitchman » Mon Apr 16, 2012 7:44 am

I tried to make a decent comparison between a V antenna paired to a 9dbi Yagi and a Skew planar antenna paired to 6 turn Helical.
The linear was tested on a cloudy day with no wind and the CP was tested on a nice sunny day but it was windy and I was getting dealt to when I dropped down to tree level over the river. The most notable thing is flying up under the power lines (110kv)
I had the SPW on the wingtip of a 2 meter foam glider which was not ideal because of the drag but I wanted to see if it was worth a permanent change. i am going to make a new 6 turn Helical and see if I can get better performance.
In my opinion at 1010mhz the jury is still out on whether the extra drag is worth it.

http://www.youtube.com/watch?v=cvIWu-TKmGY

Let me know what you think guys and I was wondering if anyone else has compared linear to CP at lower video frequencies, I am almost certain 2.4ghz and above it is almost compulsory depending on where you fly.

Mark
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Re: Linear vs circular polarization - Comparison video

Postby RCModelReviews » Mon Apr 16, 2012 8:22 am

Were you using a skewed planar (4-element) or cloveleaf (3 element) on the plane?

Unfortunately, as you've likely discovered, the CL antennas get pretty big and unwieldy at the lower frequencies so there is a trade-off.

As you've probably also noticed, the SP has a very low gain so with all else being equal, you'll likely get a little less absolute range, although the degradation in signal strength tends to be more progressive and predictable than with linearly polarized antennas.

I intend to run two FPV packs (one with linear polarization, the other with circular) on my HK EPP FPV model in a week or so and record both video signals. That should make it easy to get an absolute comparison - at least on 5.8GHz.
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Re: Linear vs circular polarization - Comparison video

Postby Mark Hitchman » Mon Apr 16, 2012 9:43 am

Yes it is a SPW 4 lobe, if I had of thought I would have used the Yagi on diversity to check against the helical because my helical is pretty rough :) 3dbi down for the yagi going linear to CP would have been interesting. The linear setup I used has been 10km at 12 meter altitude, will try the CP setup soon in this noise free area. Look forward to your 5.8ghz test on the HK EPP model. I don't know if you have seen this thread about you and your backpack circuit on FPVLab.
http://fpvlab.com/forums/showthread.php ... -esc-noise

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