This is an early design sketch of a UHF (70cm - 440 MHz) WSPR beacon.

This design comes from Ismo (OH2FTG).

Key Points

  • 10 MHz OCXO TCXO powering the Si5351 module instead of the usual 25 or 26 MHz 0.5 ppm TCXO.

  • Si5351 generates 217 MHz output, which we double to ~434Mhz using the https://techlib.com/files/diodedbl.pdf technique.

  • Use 440 MHz SAW filter at the output (from LCSC)

  • Modulation is continuous phase 4-FSK, with 1.4648 Hz tone separation.

    Since tone separation will also double with the above circuit, we have to make appropriate changes in the base stage (Si5351).

  • INNOTION MMIC as the driver

  • Use Mitsubishi RD15HVF1-501 MOSFET as finals

  • Easy and more than 1W RF output?

Status

Results: To be built and tested soon!