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Thread: Developing the Ultimate FPV Video Link

  1. #51
    Quote Originally Posted by FPVer View Post
    Can you buy the super alulah 2.1 now?
    Not yet. The 2.0 (with non-detachable wings) I think yes. Just contact Bluefalconhollan at RCG.

    Quote Originally Posted by FPVer View Post
    is that heatshrink?
    white: 5mm PVC tube, heated with heat gun to make it fit over the SMA. Once cold it is strong and with a really tight fit. No need for glue.
    black: Standard heatshrink. Just for aesthetics.

  2. #52
    Quote Originally Posted by kev.au View Post
    Wish i could build stuff that looked as nice as that.
    Not that dificult. I can guide you step by step if you want. None of the steps requires being a soldering master, or whatever.

    On the other hand, it is true that I am a bit perfectionist. My sister used to say I had got an obsessive-compulsive disorder.

  3. #53
    could quit if I wanted to volto's Avatar
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    Wow that SPW looks great. Nice work!
    Don't steal, the government hates competition.

  4. #54
    I have just received the final test report for the 4 Skew Planar Wheels I built. I am going to concentrate on the first sample, as the results for the 4 are very similar.

    This first sample (SPW1) was built for 2510MHz, RHCP.




    As we can see from the Reflection Parameter (SPW1 is the red line), the central frequency is very accurate, and the bandwidth (the value where the curve falls below -10dB) is from 2.25GHz to 2.9GHz approximately.




    Regarding the directivity and the gain, the measured gain is 2.34dB, and the antenna has got the typical “donut” pattern, omnidirectional in the XY plane, and with a null along the Z axis.




    Regarding how the antenna rejects the opposite polarization, the following graphs show the relative gains for RHCP (black line) and LHCP (red line). In the XY plan the axial ratio is quite good, >12dB in the 360°.




    In the YZ plan, the axial ratio is not as good when we approach 0° or 180°, but it is not relevant for my application, as one of the two antennas will be always working in the maximum gain region (45°-135°).




    I have requested my colleagues a 3D plot of the axial ratio for better visualize this, but the conclusions are already quite clear.

    So, the Skew Planar Wheel or Pinwheel is a fantastic omnidirectional circular polarized antenna, but in order to avoid the nulls in the main axis, you should work with two transmitters and two antennas as explained along this thread (and at the same time you would also avoid signal blocking from conductive parts of the plane).

    They are now testing my ruggedized version, to check if the epoxy and paint affects the performance. Let’s see…





    P.S. Big thank you to Old Man Mike, IBCrazy and Sander Sassen. You all rock.

  5. #55
    For Sander’s eyes only:

    Test results for the double patch from Luxul.






    Reflection: Red line is the left port, blue line is the right port (looking from the back). Worst VSWR than the SPW!!! And the bandwidth nearly misses the desired 2370MHz.





    LEFT PORT
    Gain: 11,51 dBi (@ 2510MHz)
    Beam width: Horizontal 60.8°, Vertical 34.8°
    RHCP







    RIGHT PORT
    Gain: 10,77 dBi (@ 2370MHz)
    Beam width: Horizontal 68.4°, Vertical 37.8°
    LHCP





    So, it is a good antenna, but I am going to start thinking about building a pair of circular polarized yagis, one RH for 2510MHz and another LH for 2370MHz.
    Last edited by sircana; 5th October 2011 at 06:25 PM.

  6. #56
    Engineer for Jesus Christ IBCrazy's Avatar
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    Want to try a pentalobe sphere? It is my latest optimized CP omni. Better axial ratio and slightly higher gain thean the skew-wheel. It's a bit tough to build, though. It will help with RP rejection.

    -Alex
    If it is broken, fix it. if it isn't broken, I'll soon fix that.

    videoaerialsystems.com - Performance video piloting

  7. #57
    Quote Originally Posted by IBCrazy View Post
    Want to try a pentalobe sphere? It is my latest optimized CP omni. Better axial ratio and slightly higher gain thean the skew-wheel. It's a bit tough to build, though. It will help with RP rejection.

    -Alex
    Thank you Alex, but I believe the pair of SPWs on board and the Luxul CP patch on ground is good enough for me (at this moment). After the flight tests I will decide if I move to CP yagis on the ground, and I still hope I will be able to develop a microstrip, CP, omni antenna for the plane. I have just started to play with the CST Microwave Studio. Learning a lot!!!

  8. #58
    Quote Originally Posted by sircana View Post
    As we can see from the Reflection Parameter (SPW1 is the red line), the central frequency is very accurate, and the bandwidth (the value where the curve falls below -10dB) is from 2.25GHz to 2.9GHz approximately.





    They are now testing my ruggedized version, to check if the epoxy and paint affects the performance. Let’s see…






    Well, it does affect...



    The epoxy and the paint have moved the resonant frequency from 2510 to 2610MHz, the bandwidth has decreased (now is 2470-2800MHz) and the Return Loss is not as good (but -17dB is still a very good value). The antenna would be usable for 2510MHz, but I am going to build another one changing the dimensions accordingly to see if I can match it to the desired frequency.

    There is always the option of using the "naked" version:



    But definitely it looks too fragile (and less professional ) for me. I have already broken two from my first batch just handling them.

    I will keep informing...

  9. #59
    Navigator FPVer's Avatar
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    Very nice research, you are very fortunate to have those facilities at your disposal.

  10. #60
    His Royal Sassiness ssassen's Avatar
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    I'm a little jealous actually ...
    Purveyor of the FPV secret sauce at ImmersionRC

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