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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. AE4G

    AE4G XML Subscriber QRZ Page

    [​IMG]

    A new very compact VLF antenna concept has been developed by the Department of Energy. I wonder if this would be economically reproducible for amateur VLF or even 160 meters?

    The full article is available from phys.org at:
    https://phys.org/news/2019-04-slac-compact-antenna-radios.html

    It says, in part:

    A new type of pocket-sized antenna, developed at the Department of Energy's SLAC National Accelerator Laboratory, could enable mobile communication in situations where conventional radios don't work...

    While today's most powerful VLF technology requires gigantic emitters, this antenna is only four inches tall...

    "Our device is also hundreds of times more efficient and can transmit data faster than previous devices of comparable size," said SLAC's Mark Kemp, the project's principal investigator. "Its performance pushes the limits of what's technologically possible and puts portable VLF applications, like sending short text messages in challenging situations, within reach."
     
    KK4HPY, IU1JRA, K9SS and 3 others like this.
  2. KC8EQF

    KC8EQF Ham Member QRZ Page

    We need to find in ourselves the ability to bend the law of physics and use it to build a better mousetrap
     
  3. DL3PB

    DL3PB Ham Member QRZ Page

    " In tests that sent signals from the transmitter to a receiver 100 feet away, the researchers demonstrated that their device produced VLF radiation 300 times more efficiently than previous compact antennas and transmitted data with almost 100 times greater bandwidth."

    Not sure about this novel approach yet. In the world of conventional VLF antennas one would call that a near-field test and not expect
    anything spectacular, no matter how good it is at such distance.
    73
    Peter
     
    K0UO, WQ4G, KC7HDE and 3 others like this.
  4. W1YW

    W1YW Ham Member QRZ Page

    Near field and earth-wave. It is bogus to say the antenna is "4 inches". Its not an antenna. Its a resonator being driven as an exciter. Read the Nature article.

    Basically its about a new method for making a TRANSMITTER, not an ANTENNA.

    The resonator is coupling to ground.

    GW Pierce would be proud;-)
     
    Last edited: Apr 12, 2019
    KC8NDA, WQ2H, DM1KW and 9 others like this.
  5. DL3PB

    DL3PB Ham Member QRZ Page

    If that fence(?) in the background is made from metal, 'bogus' is a kind understatement.
    Peter
     
    KR3DX likes this.
  6. K4PIH

    K4PIH Ham Member QRZ Page

    That's a big pocket!
     
    N6VL, HI8ESF and KA0HCP like this.
  7. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    The original title:
    "A High Q Piezoelectric Resonator as a Portable VLF Transmitter"

    The original article: https://www.nature.com/articles/s41467-019-09680-2

    Reiterating what W1YW pointed out, the authors do not make any claim regarding a new antenna device. Yet another failure to grasp the idea by journalists writing summary pieces.
     
    K0UO, KK4HPY, MW1CFN and 4 others like this.
  8. KD2INX

    KD2INX Ham Member QRZ Page

    I’d like to talk to them about 160 meters. That is a band that is hard to talk on. May be I’ll take all there broken
    Crystals and grind one for 160 meters
     
    KK4HPY, W4EO and KA0HCP like this.
  9. AE4G

    AE4G XML Subscriber QRZ Page

    Fair enough on the semantics of the phys.org article.

    If, however, this device (resonator or otherwise) works and could be economically employed for amateurs it could be a great thing for low band participation.
     
    KK4HPY, KC7HDE and WB6JHI like this.
  10. KE4YMX

    KE4YMX Ham Member QRZ Page

    i'm getting to tinker with the new Kymeta flat panel antennas,, it's pretty cool concept on how they manipulate the suspended particle in the liquid to be able to peak up on the ku bird. On the legacy satellites with lesser power it is not as efficient as traditional parabola dish type however with the new HTS o3b constellation the pairing is perfectly and i'm getting as much throughput as the 1M parabola stabilized dish.. BUC size being the same of course.
     
  11. W1YW

    W1YW Ham Member QRZ Page

    What..are..you...talking about?

    "...suspended particle in the liquid"? Metamaterials spoken here.... no idea what you mean by this.

    Definitely NOT as efficient as a Fourier aperture.

    You need to look at the sidelobes. Not pretty.
     
    NU4R likes this.
  12. WA2LXB

    WA2LXB XML Subscriber QRZ Page

    Those are some fascinating antennas.
     
  13. KQ6XA

    KQ6XA Ham Member QRZ Page

    Those of us who have worked in the LF and ultrasound/ultrasonic industry are somewhat familiar with the electromagnetic radiation (radio waves) that are emitted by piezo elements.
    They've taken this principle a big step further here, and amplified that effect a lot :)

    Congratulations to: Mark A. Kemp, Matt Franzi, Andy Haase, Erik Jongewaard, Matthew T. Whittaker, Michael Kirkpatrick, and Robert Sparr!

    Some factoids boiled down from skimming the article:
    1. A lithium niobate piezo rod is held in a fixture (with a metallic toroid at the top to shape the field).
    2. The fixture can be inside a vacuum or insulating gas container.
    3. The piezo rod is utilized as oscillator-transmitter-antenna by excitation with a function generator.
    4. The piezo rod mechanically/acoustically oscillates at around 35 kHz.
    5. It also radiates electromagnetic waves (radio waves) at around 35 kHz.
    6. The radio waves can be picked up at some distance away
    7. This method of using a piezo as a miniature transmitting antenna at LF seems to be more efficient than a conventional miniature transmitting antenna of the same size.
    8. Voltage developed across the crystal is 125 kV.
    9. Input voltage is 5.3 V
    10. Input impedance is 110 Ω
    11. Average power dissipation is 120 mW.
    12. The piezo has a Q of about 300,000 or more.
    13. For 2FSK, the piezo element's oscillator self-resonance is pulled ~7 Hz by a relay/capacitor circuit in synchronization with the function generator.
    14. Slow baud rate Frequency Shift Keying is shown.
    15. Some 2FSK symbol rates are shown in the article:
    • 0.2 symbol per second
    • 4 symbol per second
    • 100 symbol per second
    • [​IMG]
     
    Last edited: Apr 12, 2019
    WQ4G, G6FLW, AB2YC and 3 others like this.
  14. W1YW

    W1YW Ham Member QRZ Page

    Antennas are about gain and power pattern.

    Lets say that the antenna you mention was , oh, 60% efficient.

    Then to get the same gain, the area would have to be increased by over 66% to get the same gain as the paraboloid.

    That means you would have to make it 30% bigger in diameter.

    That mean the cost would increase by roughly 50%.

    That means the power needed to electrically steer the antenna would increase by at least 25%.

    That means the itchy sidelobes would increase by roughly 30%.

    Phased subarrays are flat, take less power, and are more efficient.

    Don't confuse a matched filter with equivalent performance of an antenna.

    FYI...
     
    NU4R likes this.
  15. W1YW

    W1YW Ham Member QRZ Page

    Like the old days: using mechanicals to drive electromags.... Maybe we should take a fresh look at Alexanderson generators;-)
     
    WQ4G and NU4R like this.

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