• Low-Cost  WSPR with Raspberry Pi and SDR (pdf)
    • A presentation I gave at the March 11 meeting of the San Juan County Amateur Radio Society.
    • Key points:
      • WSPR transmitter using Raspberry Pi is cheap.  The antenna feedline may cost more than the transmitter
      • This is not your traditional transmitter!  The output is essentially a sampled squarewave.  There are all the usual odd harmonics, but there are also harmonics that, due to sampling / aliasing can end up very close to the carrier.   Spurious outputs will vary, depending on the output frequency.
      • Receivers can be made using inexpensive Software Defined Radios and cheap computers.  Total cost for new gear can be under $150.
      • A network connection, or a local GPS are required for both the transmitter and receiver.  WSPR depends on precisely-timed transmitters and receivers.