I assume most of us know that circular polarized antennas are great for FPV video streams because they're good at rejecting out of phase signals. Thankfully you can buy these most of these antennas now, and even better yet, you can make your own with a little bit of work.
Probably the most popular design is the clover leaf, however I always hated building these, and recently found a different style of circular polarized antennas, the True R/C style by Hugo. He was nice enough to put out two how-to guides on how to build these, and I did a bit of recording on the last one I built in the hopes of helping the new antenna builder out.
PDF Guides:
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Also I'm buying an SWR meter and will be using my schools antenna analyzer. I'll be sure to share my results on different styles and frequencies.
Joe,
A person with knowledge that far exceeds mine just sent me this document on that design. I haven't had a chance to read it yet, but I wanted to share.
http://www.amsat.org/amsat/articles/w6shp/lindy.html
Joe,
I have nothing to do with Hugo or True R/C, I simply just liked the ease of building his antennas and started making my own.
Look up IBcrazy blog on rcgroups for fpvlab. (he owns videoaerialsystems). He's got some great guides on making your own SNR tools and the like, and might have some information on how to measure some of the stuff you're looking to see.
Do you and Hugo make the 5.8 GHz antenna? If so how much? I may just purchase one (or more) to play with. The tutorials at Fpvlab.com are great. Also, this has opened up new vistas for me to exploreq, especially info at http://videoaerialsystems.com/. The chart with dimensions for various frequencies is great, and I did find a pretty good web site on theory, so once I digest that hope to write a little Mathcad file and share it. Also, it will be fun to explore and build some circuits for hooking these up to the Oscilloscope, ; although Figuring out how to measure the high frequencies and get meaningful results will also be a challenge for me. Of course the easiest way to measure gain will be to just hook them up and check out thesignal in a big field prior to flight, manually verify the distance, etc.
The PDF does list the requirements for making 2.4 and 5.8 at the bottom, but Graham is right, the tolerances get tighter. I modified the 1280MHz lengths and aim for 1.2 SNR for 1253MHz and 1280MHz like the ones he sells.
He has some information here, but not exactly what you're wanting Joe.
http://fpvlab.com/forums/showthread.php?3960-Windmill-fan-tutorial!
I was doing some flying on campus and an old HAM guy came up and started talking to me about the design, so my guess is that it's just another old HAM antenna that has been around for ages. If I find the good stuff about it, I'll be sure to share it. I did ask hugo and ibcrazy the different between the two styles and didn't get a very clear answer unfortunately.
Are there any gain information about these antennas?
So I'll just make one for the jDrones telemetry instead of the video.
For 5.8Ghz, tolerances are such that your finished antenna will need tuning which requires extra equipment, the skill to know how to use it and patience to achieve a good result.
Good luck, Peter
Both the guides are for 900-1300MHz, 5.8GHz antenna's are very small relative to these and are quite hard to do, a friend got a professional jeweller to make his, otherwise you just buy ready-made ones for 5.8GHz as they are fairly easily available.
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