Shortwave listeners name bands by wavelength in metres, not by frequency. “The 31-metre band” means the frequencies around 9.4 to 9.9 MHz. The number is roughly 300 divided by the frequency in MHz: 300 ÷ 9.7 ≈ 31.
The broadcast bands
International broadcasters use these bands, set by the International Telecommunication Union. The edges below are the commonly listed ranges; stations sometimes operate just outside them.
| Band | Frequencies | Best time |
|---|---|---|
| 120 m | 2300–2495 kHz | Night (tropical regional stations) |
| 90 m | 3200–3400 kHz | Night (tropical regional stations) |
| 75 m | 3900–4000 kHz | Night |
| 60 m | 4750–5060 kHz | Night |
| 49 m | 5900–6200 kHz | Evening and night |
| 41 m | 7200–7450 kHz | Evening and night |
| 31 m | 9400–9900 kHz | Around the clock, best evenings |
| 25 m | 11600–12100 kHz | Day and early evening |
| 22 m | 13570–13870 kHz | Daytime |
| 19 m | 15100–15800 kHz | Daytime |
| 16 m | 17480–17900 kHz | Daytime |
| 15 m | 18900–19020 kHz | Daytime |
| 13 m | 21450–21850 kHz | Daytime, best near solar maximum |
| 11 m | 25670–26100 kHz | Daytime, rarely used |
The pattern follows how the ionosphere behaves: low bands at night, high bands by day. The 31-metre band sits in the middle and is the busiest band most of the time.
The tropical bands
The 120, 90 and 60-metre bands are called the tropical bands. They were set aside for domestic broadcasting in tropical countries, where thunderstorms make medium wave noisy. Many of those stations have moved to FM, so these bands are quieter than they were, but they are still where to look for distant regional stations at night.
Not just broadcasting
Between the broadcast bands are frequencies for aviation, shipping, amateur radio and time signals. Two you can hear any time: the WWV time signal on 5, 10 and 15 MHz, and Shannon VOLMET, the aviation weather broadcast. Amateur radio has its own bands too; the 20-metre FT8 frequency is one of the busiest.
Reading a schedule
Shortwave schedules use UTC and change twice a year, at the end of March (the “A” season) and the end of October (“B”), as broadcasters follow the seasons. Skywave DX reads a published schedule and shows what is on the air at this minute, so you don’t have to convert time zones.