Ever hear of the new "fractal antenna" designs ?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KD7SIZ, Dec 15, 2010.

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  1. K4WGE

    K4WGE Ham Member QRZ Page

    Invisibility now!

    The "cloaking device" then, according to the narrator Nathan Cohen of Fractal Antenna Systems, does not work in three dimensions nor in visible light, and from what the video demonstrates, the device itself is visible and many times the size of the object to be made "invisible".:confused: Is that right?
  2. W8JI

    W8JI Ham Member QRZ Page

    What is goofy is the measurement method. The measurement method does not support the theoretical conclusion.

    The place a source antenna and a detection antenna in the Fresnel region of the cloaking device and claim some slip stream effect like air would have.

    There are at least two reasons it would behave like it does, neither of which have anything to do with cloaking.

    If we wanted to prove cloaking or slip stream of the microwave, we would have to measure the field at multiple points multiple ways. Also it is useless if it does not stop re-radiation back toward the source.

    The single point measurement shown means almost nothing.

    73 Tom
  3. W1YW

    W1YW Ham Member QRZ Page


    Why don't you tell me all about my 40M fractal that's up now?

    How big is it?

  4. W1YW

    W1YW Ham Member QRZ Page

    No doubt, but feel free to articulate the math that backs it up. Happy to help you through it.

  5. W1YW

    W1YW Ham Member QRZ Page

    Nope. Not true. There are no HF fractal antenna designs "all over the web".

    If people want them, I will publish hem. So far, the demand is clearly DIY VHF/UHF.

  6. W1YW

    W1YW Ham Member QRZ Page

    How? Where is the RF source? Inside? Outside?

    The RF is ducting, wideband,to the antipodal point, from the outside.

    It is not a single point measurement. Full scattering measurements are being published. The video makes it very clear there is a second part that will be shown after publication of the scattering data.

    Chip W1YW
  7. K1BQT

    K1BQT Ham Member QRZ Page

    Interesting experiment -- sounds like a variation on what Alitalo and Tretyakov did at Helsinki in 2008 and many other people are currently working on -- broadband cloaking using pc materials with printed aperiodic structures. Guess time will tell if a fractal proves to be the optimal shape.
  8. N3OX

    N3OX Ham Member QRZ Page

    Probably big enough to not be in the "very electrically small" regime.

    After all,

    Pretty much what I know about your 40m antenna is that it exists and isn't "pretty darn big" for your preferred value of "pretty darn big." I'm confident that it's not "electrically tiny." I'm sure the assembled antenna doesn't fit in a 1/50th wavelength long, 1/80th wavelength diameter cylinder like a certain popular commercial 40m "antenna".

    Some prior posts have made it pretty clear to me how you feel about people who are looking for very electrically tiny antennas.

    Maybe N5RWJ doesn't care about that at all, so go ahead and answer his question.

    In retrospect, I should have left out the "darn."

  9. W1YW

    W1YW Ham Member QRZ Page

    Perhaps you can articluate the process by which 'time tells'?

    And no; it is not anything like that. But I would be HAPPY to discuss that article publicly with you here Rick, including the mathematics, in good spirits, of course!

    So, why don't you start us off--no collaborations please--
    and we can all enjoy a delightful, technical discussion on that paper.

    Chip W1YW
  10. W1YW

    W1YW Ham Member QRZ Page

    It's not an MI2. It is electrically small. It is NOt very electrically small. It loses about 2 dB compared to a lossless version. However it has 6 dB of gain, to more than compensate the loss and allows me to get the bulk of the current distribution as high as possible, thereby render many, many dB improvement at low angles, compared to an inverted V, foe example. In addition, I use proprietary ground screens that lower the launch angle.

    I really don't care if some alleged 'expert' here--not you OX--thinks that's BS or goofy or not.

    The real question is: what do HAMS want to see in better antennas? The answer is NOT at MF or low HF. You and I might want that, but the bulk of hams don't give a darn about that. They want DIY VHF/UHF.

    That's ham radio today...not ham radio for the "OM" retired set. Observation--not criticism.

    Last edited: Jan 20, 2011
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