Low power long range radio communication

By combining several factors, you really can achieve amazing results;

  • Collect the RF power to an extremely narrow bandwidth
  • Low modulation rate allowing the receiver to integrate over time
  • Using a frequency high enough to penetrate the D-layer with low losses
  • Using a frequency low enough to refract in the F2 layer
  • Timing the ionospheric conditions according to D- and F2 layers
  • Generous forward error correction coding

(image source

This above is a digital transmission of 0.1 watt (20dBm) from Sweden to Australia, over 15000km using the WSPR protocol. For comparison, your cell phone uses many times this transmission power. :-)

  • 6 Hz (sic) modulation bandwidth
  • Modulation 4-FSK
  • 50 bits payload transmitted over just under 2 minutes time
  • Modulation speed ~1.5 baud
  • Data speed ~0.5 bps
  • 28 MHz carrier
  • Vertical (omnidirectional) antenna

Not any data rates you may surf the web with, but I find it amazing you actually can transmit messages literary across half the world, without any infrastructure, using almost undetectable RF power and equipment available to more or less everyone.

/By Mikael Q Kuisma


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Page last modified 2015-06-30 19:30Z