Digital mode frequencies

Dial frequency and audio offset

Digital modes are sent as audio through an SSB transmitter. The frequency in the table is the dial frequency, the suppressed carrier, with the radio in USB. Your signal appears above it by the audio offset you choose in the software. With FT8 on 20m, a dial of 14.074 MHz and an offset of 1,500 Hz puts your signal on 14.0755 MHz. FT8 signals spread across about 3 kHz above the dial frequency, so the whole sub-band is about 14.074 to 14.077 MHz.

Use USB on every band, even below 10 MHz where voice uses LSB, because the software expects it. Keep the radio's speech processor off and the audio level low enough that the ALC meter barely moves. Overdriving the audio creates extra signals that interfere with other stations.

Which mode should I use?

• FT8 is the most popular, with 15-second overs that decode signals well below the noise. It's ideal for making lots of contacts and checking propagation.
• FT4 is a faster version with 7.5-second overs, designed for contests.
• WSPR is for testing propagation, not contacts. Stations send low-power beacons that are reported to wsprnet.org, so you can see where your signal reaches.
• JS8Call uses the same kind of signal as FT8 but lets you type free-form messages and relay them through other stations.
• PSK31 and RTTY are older keyboard modes for live typed conversations, still popular in contests and for ragchews.
• SSTV sends pictures. The ISS sometimes transmits SSTV images on 145.800 MHz FM.

Time and accuracy

FT8, FT4 and WSPR need your computer's clock to be within about a second of the correct time. Use an internet time service or a GPS receiver, and check it before you start. If you can see signals but decode nothing, the clock is the most likely cause.

Questions