6 Jan 2019

Earth-mode VLF

Yesterday, I mentioned amateur VLF experiments below 9kHz. A very accessible introduction is earth-mode communications, especially utilities assisted earth mode. Using the latter mode, 6km has been spanned,  with just 5W, although much further should be possible. With much higher power and larger baselines at the TX end, I expect the small radiated power will be detectable hundreds of km away, although this is not going to be earth-mode.

An example of a typical earth-mode VLF transmitter is shown at the link.
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2 comments:

  1. Ken MaySun Jan 06, 04:44:00 pm GMT

    Hi Roger,
    maybe a GPS disiplined QRPLabs WSPR beacon fed to this amplifier would allow you to leave a beacon running that could be decoded at remote sites by others. This would be a good way to restart this hobby. There have been a lot of improvements since you last tried this frequency.
    I still have all my kit I built to your original plans.

    73 Ken G4APB

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  2. Roger G3XBMSun Jan 06, 07:47:00 pm GMT

    Ken - you are right that a GPS disciplined source is a good idea. WSPR would not be the best as far narrower bandwidths and far longer time periods would be needed. With a GPS source very narrow bandwidths would be possible and very long integration times (even days). My problem these days is my health - I am just too "foggy" (see https://sites.google.com/site/g3xbmqrp3/stroke). It would be good for someone else to try!

    73s Roger G3XBM

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