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Thread: NEW Antenna design " The latest and greatest"

  1. #11
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    Not a bad reduction in efficiency at all. I am impressed.


    What about the signal efficiency (meaning the voltage stressed efficiency). Think of it like this: you are energizing the air with your tx antenna at a certain distance to your RX, your strength is in the order of uV/meter. The greater the size of your antenna, the more voltage that gets back to the VRX as the antenna phisically covers more area. Does the sub made system get excited just like a normal helical?

    The reason I am asking is because a helical in axial mode has a signal that winds down it's coil creating a dipole effect at multiple intervals along the coil. The signal doesn't really travel down it, but across it. With the stubs, the winding in this fashion is interrupted, but right now I can't figure if the stubs allow for the same dipole effect by acting as energized protions within the cone. I have been curious about this design for a while, but haven't been able to visualize it and how it overcomes the reduced voltage stress issue. Maybe you can enlighten me?

    -Alex

    Quote Originally Posted by Kondor-FPV View Post
    Hello Alex,
    to answer your questions, the antenna is 65% efficient at center frequency 1360mhz. Its a bit less than the 72% efficiency of my full size 6 turn 1.2.
    I found that if you keep the circunference of the base within 66% λ efficiency stays acceptable. If you go down to 50% it will degrade significantly.
    That's why the helical is 1/3 the size of a regular one (pitch angle α is only 8) . Luxul is able to achieve similar efficiency and make it 1/4 the size. I don't know how they do it , but for our frequencies this is plenty small. I don't have a robotic arm to bend with such precision as they do

    My tapered microstrip isn't backwards, but you probably meant it's horizontal as opposed to vertical, and works pretty much the same, but makes antenna more compact at the bottom.

    The frequency sweep is sinusoidal with short intervals. I would have preferred if it weren't as narrow band, but I was spot on with the calculations, just got lucky I guess. It's a real nightmare to build, and I don't know if I will offer it, I mean what should I charge for something that takes away a day of your life?

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

    [url]videoaerialsystems.com[/url] - Performance video piloting

  2. #12
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    Quote Originally Posted by Kondor-FPV View Post
    While I was making this, I thought "how nice would be to make a stub-loaded SPW) so the 900mhz SPW would be as small as a 2.4 SPW...

    That we can make if people with 3d NEC modeling experience come forward and help... say.. OMM, Hugo, Alex, Mictronics.
    I thought of this, but ran into the dielectric issue. As you know using a dielectric allows for a smaller antenna, but at efficiency reduction equivalent to it's relative size.

    The CL and SPW work very differently than the helical in operation. They use a dynamic loop antenna structure similar to the Quagi and BiQuad that Hams have used for years. Perhaps a little research into the operation of the square full wave antenna will give the answer.

    The way a loop antenna works (assuming a full wave loop) is the current reverses direction halfway through the loop. That phenomenon causes the loop to appear energized on two sides rather than just one making a parallel dipole effect. Changing the strutcure design theoretically maintains the same conditions in theory, but in practice I have found outherwise when I tried a triangular structure. However, the CL/SPW structure allows for this reversing effect without penalty (hence why the lobes are rounded), and where HugeOne's are square similar to the quad loop. If we can figure out a structure that reduces the size of the quad loop, we might find the answre to reducing the size of the CL/SPW and a bunch of other antennas.

    Now where is OMM? This is a job for him. It's over my head.

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

    [url]videoaerialsystems.com[/url] - Performance video piloting

  3. #13
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    Might be a stupid question from a non antenna expert.


    EDIT:
    And it was....
    Last edited by man2000me; 31st May 2012 at 04:01 PM.

  4. #14
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    lulz... that made no sense and i have no clue what they are saying.

    For us idiots, we should stick to flying through things, fast.

  5. #15
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    hahah I see how it is. Hope your ready for the meet. We have some hole flying to do.

  6. #16
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    Quote Originally Posted by IBCrazy View Post
    Not a bad reduction in efficiency at all. I am impressed.


    What about the signal efficiency (meaning the voltage stressed efficiency). Think of it like this: you are energizing the air with your tx antenna at a certain distance to your RX, your strength is in the order of uV/meter. The greater the size of your antenna, the more voltage that gets back to the VRX as the antenna phisically covers more area. Does the sub made system get excited just like a normal helical?

    The reason I am asking is because a helical in axial mode has a signal that winds down it's coil creating a dipole effect at multiple intervals along the coil. The signal doesn't really travel down it, but across it. With the stubs, the winding in this fashion is interrupted, but right now I can't figure if the stubs allow for the same dipole effect by acting as energized protions within the cone. I have been curious about this design for a while, but haven't been able to visualize it and how it overcomes the reduced voltage stress issue. Maybe you can enlighten me?

    -Alex
    Hello Alex,
    There are indeed small discontinuities across the stubs both in current magnitude and phase, but they are not large, so the current along the helix perimeter is about the same as that in a regular Helix.
    The current phase is quite non-linear just like a regular helix.

    The stubs provide a phase shift in addition to the natural phase progression along the helix.

    The stubs pretty much serve to correct the phase introducing step changes to approximate the Hansen-Woodyard condition, since the natural phase progression would not be enough to satisfy it.
    [url]www.fpvlr.com[/url] - Home of your favourite Custom FPV antennas.

  7. #17
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    Looks really nice. I want one!

  8. #18
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    I want one for 1280

  9. #19
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    Wow!! Congratulations!! I wish I had the patience to build a stub loaded helical...
    [URL="http://www.circular-wireless.com"]www.circular-wireless.com[/URL]

  10. #20
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    Not sure, looks like a d*ldo to me
    Velvety smooth drone pilot for hire

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