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- FSK With the Si5351 Clock Generator (a multi-page design note)
- Microhams Digital Conference 2021
- 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.
Ham Radio Tech Stuff