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Novel Compact Antenna for VLF

Discussion in 'Amateur Radio News' started by AE4G, Apr 12, 2019.

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  1. AH7I

    AH7I Ham Member QRZ Page

    Good day Mark,

    Am I correct in understanding the principle that, for the wavelengths involved, impedance matching to mechanically accelerate charge is much more efficient than impedance matching to electrically accelerate the same amount of charge?

    Thanks,

    -Bob
     
  2. MKEMP

    MKEMP QRZ Member

    That might be one way of saying it. With the piezoelectric material as the radiating element, designed appropriately, there doesn't need to be any impedance matching at resonance. Therefore, compared to a same-length of wire, you won't have any losses associated with the needed matching network (a big inductor).

    The losses associated with a conventional copper radiating element versus a piezoelectric radiating element are fairly similar. In the first case, the dominant loss is ohmic, in the second, it is elastic losses. By trying to get a high of a mechanical Q as possible, we reduce elastic losses. Unfortunately might be behind a paywall, but the group here did a nice job of analyzing this from first principles: https://aip.scitation.org/doi/pdf/10.1063/1.4975030?class=pdf

    Mark
     
    KK4HPY and KA0HCP like this.
  3. AH7I

    AH7I Ham Member QRZ Page

    Thanks Mark,
    If anyone would like to read and does not have an account,
    I found a web accessible copy at:
    https://sci-hub.se/https://doi.org/10.1063/1.4975030
    I get the advantage over matching to a conductor. There
    is still a need to couple energy in order to induce motion.
    That would be the mechanical matching I asked about.
    The other bane of short antennas, high potential gradient,
    lives on.
    73, -Bob
     
    KK4HPY likes this.
  4. ZL3DW

    ZL3DW Ham Member QRZ Page

    "Ya canna break the laws of physics, Jim" [McCoy]
     
  5. ZL3DW

    ZL3DW Ham Member QRZ Page

    My very limited knowledge of the Piezo effect is that if you apply a voltage the device moves physically and if you apply a physical pressure the device outputs a voltage. Resonating such a device is the basis of all crystal oscillators, so nothing new there. Stimulating a Piezo rod with a frequency equal to the rod's resonant frequency would therefore cause a physical vibration. In other words it would seem that this "antenna" is radiating sound waves and not electromagnetic waves. I may be wrong, but I don't believe that there is any kind of breakthrough in antenna design here.
     
  6. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    Correct. The authors never made any claims about antennas. That comes from a misleading and incorrect headline that is being repeated.
     
  7. AE4G

    AE4G Ham Member QRZ Page

    The criticism of the word "antenna" in the phys.org article is probably fair. The actual paper published by study's authors is a better source.

    However, please do note that this device is radiating RF, not sound. See quote from one of the authors of the study:

    "A quick note: we are not sending sound. For many tests we have the piezo in vacuum. This is an electromagnetic transmitter."

    I am still excited about the potential use of a similar device in amateur radio, at least in the 2200m band.


     

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