DAM direct antenna modulation

Discussion in 'Wireless & RF Design' started by BR-549, Apr 14, 2019.

  1. BR-549

    Thread Starter AAC Fanatic!

    Sep 22, 2013
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    This is more than interesting. I have been reading on this a little, but most is for GHz. I am wondering about HF, MF and LF QRP.

    And the lower VLF bands. Easy and common communication thru mountains and water is intriguing.

    Anyone fooled with this before?

    https://phys.org/news/2019-04-slac-compact-antenna-radios.html
     
  2. nsaspook

    AAC Fanatic!

    Aug 27, 2009
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    Looks more like near-field electric induction than far-field EM wave propagation.
    https://en.wikipedia.org/wiki/Near_and_far_field
    The physics of antenna radiation resistance into free space vs physical size sets hard limits on em wave efficiency even for a dielectric resonator antenna.
    https://en.wikipedia.org/wiki/Dielectric_resonator_antenna

    I used VLF stations all the time back in the 70's for fleet broadcast message reception at sea.

    https://en.wikipedia.org/wiki/Naval_Communication_Station_Harold_E._Holt
    https://en.wikipedia.org/wiki/Lualualei_VLF_transmitter
     
  3. Yaakov

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    Jan 27, 2019
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  4. nsaspook

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    The results in the actual paper mirror what I thought about near-field induction effects and antenna radiation resistance.

    https://www.nature.com/articles/s41467-019-09680-2
    [​IMG]
    https://static-content.springer.com/esm/art:10.1038/s41467-019-09680-2/MediaObjects/41467_2019_9680_MOESM2_ESM.pdf
     
    Last edited: Apr 15, 2019
  5. josephkarl

    New Member

    Apr 17, 2019
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    The frequencies are not getting enabled through the module and by the post we can see that the issue needs to be fixed. The main thing is that we have to know the basic aspects of this before implementing.
     
    Last edited by a moderator: Apr 17, 2019
  6. BR-549

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    It looks like a sine applied to rod. Then a capacitor at base of rod is switched in and out at base band rate.

    FSK at antenna.
     
  7. nsaspook

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    A fancy spark transmitter or a Alexanderson Alternator with fast frequency control.



    This DAM system is a cool proof of concept but we already know a lot (since at least 1906) about actual VLF transmission engineering. All of the generation technology can be miniaturized but the physical antenna for far-field wave propagation can't.
     
  8. Yaakov

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    Jan 27, 2019
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    We'll just use (waves hand) nano-fractal antennas with huge exposed edges in tiny spaces.

    Capture? Don't bother me with details, I am trying to get round one funding.
     
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