United Kingdom · Licence examHow does ham radio propagation work on HF?
The ionosphere is layers of ionised gas between about 70 and 400 km up, ionised mainly by ultraviolet from the sun. How they behave decides which bands open, with ham radio propagation changing through the day, the seasons and the sunspot cycle.
| Layer | Day and night | Effect on signals |
|---|---|---|
| D | Present in daylight, tends to disappear at night | Absorbs the lower frequencies by day. The lowest frequency that gets through is the LUF. |
| E | Present by day. Strong patches (sporadic E) form from May to mid-August. | One hop up to about 2,000 km. Sporadic E affects 14-144 MHz, most often 28 and 50 MHz. |
| F1 | Combines with F2 at night | Part of the F region. |
| F2 | Combines with F1 at night | The longest single hop, about 4,000 km. Several hops give worldwide contacts. |
The highest frequency that comes back over a path is the maximum usable frequency (MUF). If the LUF is above the MUF, there’s no ionospheric path at all.
The syllabus also covers ground wave, sky wave, the skip zone and near vertical incidence sky wave (NVIS), used for short-range contacts on bands such as 5 MHz.
Solar conditions and space weather
More sunspots mean more ionisation and better HF conditions. The Full syllabus also covers how solar flares affect propagation.
The RSGB’s live solar data page shows current readings, provided by N0NBH, with a link to NASA’s SOHO images of the sun. RSGB members get monthly HF propagation predictions in RadCom.
VHF and UHF: line of sight, lifts and sporadic E
- Signals usually go about a third further than strict line of sight, because they bend slightly with the Earth’s curve. Hills cast radio shadows.
- A higher antenna helps more than more power, because it improves receiving as well as transmitting.
- Tropospheric lifts come with high pressure, especially in summer, and can carry 2 m and 70 cm signals hundreds of kilometres. The best can come as pressure starts to fall from a high.
- Sporadic E is best from May to mid-August. One hop covers 1,000 to 2,000 km, it’s most often noticed on 28 and 50 MHz, and 2 m openings are rarer.
- A tip from the RSGB: listen around 100 MHz on an FM radio. Foreign-language stations can mean a 2 m opening.
What is the range of a ham radio?
It depends on the band, the conditions and your station. On VHF and UHF, range depends on antenna height, antenna gain, a clear path and power, and it drops as frequency rises. On HF, one E-layer hop reaches up to about 2,000 km and an F2 hop about 4,000 km, so worldwide contacts take several hops.
For handheld radios, the RSGB’s rough figure is 5 to 10 miles direct, or further through a repeater.
Sources: RSGB and 5 more. Checked October 2026.
- RSGB: Combined syllabus specification v1.6b, March 2026 (PDF) ↗
- RSGB: LF and HF propagation ↗
- RSGB: VHF/UHF propagation ↗
- RSGB: Live solar data ↗
- RSGB: Propagation predictions ↗
- RSGB: Buying a new transceiver ↗
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