Novel Compact Antenna for VLF

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

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  1. KA7G

    KA7G Ham Member QRZ Page

  2. KA7G

    KA7G Ham Member QRZ Page

    Does the little table have to be red?
  3. KA7G

    KA7G Ham Member QRZ Page

    Does the little table have to be red?
  4. VK6ZGO

    VK6ZGO Ham Member QRZ Page

    They continuously refer to antennas, both in the abstract & the body of the publication, so it would be extremely difficult for a "non-aficionado" to decipher what reads to me as, mainly "goobledegook".
  5. VK6ZGO

    VK6ZGO Ham Member QRZ Page

    Yep! Alexanderson's alternator was a very interesting design---he even managed to amplitude modulate it in several tests.
    It was at least, a source of real CW signals, in contrast to "spark" & its various derivates.

    He used completely normal wire antennas, devising one particular "compact" (In relative terms only), antenna which was used as a standby antenna at the AM Broadcast site I worked at
    Its official name was a "Triple Tuned Alexanderson".

    Although its main elements were horizontal, most of the current flowed in three vertical conductors,
    so it was vertically polarised.
    The vertical elements were close enough together in terms of a wavelength, that it was substantially omni-directional.
  6. DM1KW

    DM1KW Ham Member QRZ Page

    My conclusion is that the piezo-crystal is solely used as a coupling device, offering a real resistance at resonance frequency. There's a field shaping toroid on the top of the crystal. What would happen if this would be extended to a longer wire/capacitance hat (length<lambda/4). Would the mechanism cancel out the added capacitive resistance? If this is the case I would understand what could be interesting about it: efficiency compared to lumped element tuners.

    KK4HPY and KA0HCP like this.
  7. WQ2H

    WQ2H QRZ Lifetime Member #214 Platinum Subscriber Life Member QRZ Page

    "Pocket size" for 2200m - odd, but that's not even remotely on my list........

    Nathan's got it straight. Big difference between an antenna and a excited resonator.
  8. MKEMP

    MKEMP QRZ Member

    A different piezoelectric material can demonstrate the concept. However, we chose LN because of its exceptional Q, high breakdown strength, and high mechanical strength. PZT is an alternative, but would limit Q to 1,000 or 2,000 or so. The whole point is that we must get much higher Q and lower system volume than what is possible with a same electrical size "conventional" transmitter and antenna. Our customer has specifications for which we are working to meet, not necessarily as a direct 1-1 replacement for what's already out there.

    We claim the LN itself behaves as a Hertzian dipole. The same disadvantages of extremely short conventional electrical dipoles apply here, except the input impedance is now ~150 Ohms rather than >-j*10^6 Ohm @ 30 kHz with an enormous inductance to provide a match.

    Not all resonators will radiate. We designed this resonator geometry to be a very short electric dipole. If there is data or analysis to the contrary to what we presented, I'm happy to attempt to address. The whole reason we presented this as open access was to welcome comments and analysis from those that might not have access behind the paywall of some of these journals.

    KK4HPY and VK6ZGO like this.
  9. DM1KW

    DM1KW Ham Member QRZ Page

    To me this is the most important statement.
    KK4HPY and AH7I like this.
  10. SM0AOM

    SM0AOM Ham Member QRZ Page

    Alexanderson was the inventor of the "multiple tuned antenna"
    which first was described in the 1919 paper "Transatlantic Radio Communication", Trans. AIEE.

    He was the first to utilise the distributed nature of ground system losses, and the improvement in antenna efficiency possible by using multiple tuning. In theory, the antenna efficiency of an electrically very small antenna improves with the square of the number of tuned circuits.


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