VOA Radiogram: The rule of FUM (Fastest Usable Mode)

Thanks to everyone who sent reception reports, screenshot, audio samples, and other attachments after listening to VOA Radiogram during the weekend of April 27-28.

After six weeks of experimenting with digital text modes, I think we can conclude that the PSK modes are good, MT63, Olivia, and Thor are better, but MFSK remains the best.

We can coin a new acronym: FUM – Fastest Usable Mode. It appears that these would be our FUMs:

  • MFSK16 (58 wpm): when poor reception conditions are expected
  • MFSK32 (120 wpm): when fair reception conditions are expected
  • MFSK64 (240 wpm): when good reception conditions are expected
  • MFSK128 (480 wpm): when perfect reception conditions are expected (eg local FM or AM)

During reception of the Sunday 1930 UTC broadcast on 15670 kHz, I experienced a poor signal (being in the skip zone), moderate fading, and local noise. Excellent conditions to test digital text modes. This audio excerpt shows how MFSK16 provided a perfect decode even in these conditions. The Fldigi readout is below, showing MFSK64 on top, MFSK16 on the bottom: