What HF radio means
HF stands for high frequency. The International Telecommunication Union uses the name for frequencies between 3 and 30 MHz. The range is also called the decameter band, because wavelengths run from about 100 meters to 10 meters, and it overlaps heavily with what is often called shortwave radio.
HF is best known for long-distance communication. Under suitable conditions, signals can travel hundreds or thousands of miles without any repeater, satellite or internet connection. To see how that compares with other ranges, read Is Ham Radio UHF or VHF?.
How HF works
HF signals travel in two main ways:
- Ground wave: The signal follows the surface of the Earth. This is most useful at the lower HF frequencies and gives limited range, often tens of miles.
- Skywave: The signal travels upward and is refracted by layers of the ionosphere, returning to Earth far from the transmitter. This is sometimes called “skip”. It is what allows intercontinental contacts.
Because the ionosphere is ionized mainly by the sun, HF conditions change with the time of day, the season and the solar cycle. In general, higher HF bands tend to work best in daylight and when solar activity is higher, while lower bands often work better at night. A single band may be open to one region and closed to another within the same hour.
For numbers and examples, see HF radio range in miles.
The HF amateur bands
Amateur radio shares the HF spectrum with many other services. The commonly used US HF amateur bands are:
| Band | Approximate frequencies | Notes |
|---|---|---|
| 160 m | 1.8-2.0 MHz | Technically MF, often grouped with HF by hams |
| 80 m | 3.5-4.0 MHz | Often active in evenings and nights |
| 60 m | Channels near 5.3 MHz | Limited channels |
| 40 m | 7.0-7.3 MHz | Works day and night |
| 30 m | 10.1-10.15 MHz | CW and digital modes only |
| 20 m | 14.0-14.35 MHz | Popular for worldwide contacts |
| 17 m | 18.068-18.168 MHz | |
| 15 m | 21.0-21.45 MHz | Depends more on solar activity |
| 12 m | 24.89-24.99 MHz | |
| 10 m | 28.0-29.7 MHz | Varies strongly with the solar cycle |
Which parts of each band you can use depend on your license class and country. The segments and modes are described in band plans, similar to the 70cm band plan.
Is HF the same as ham radio?
No. HF is a frequency range, and ham radio is a service that operates in many ranges, including parts of HF, VHF, UHF and beyond. Many HF users are not hams, including international broadcasters, aviation, maritime, government and military users.
Other HF users
- Shortwave broadcasting uses HF for international programs.
- Aviation: Long-range aircraft use HF voice on oceanic routes. Shanwick Radio, for example, handles North Atlantic communications, and uses assigned HF frequencies that change by region, time and need. Check current published frequencies rather than relying on a fixed number.
- Frequency hopping: Some professional and military systems change frequencies rapidly in a pattern to resist interference. That is different from ordinary amateur voice operation.
- Time stations broadcast standard time signals.
What you can do on HF
Hams use HF for:
- Voice (SSB) conversations
- Morse code (CW)
- Digital modes such as FT8
- Contesting and awards chasing
- Emergency and disaster communication when local networks are down
- Experiments with propagation and antennas
Basic equipment
A typical HF station has a transceiver, an antenna, feedline, a power supply and often an antenna tuner. Wire antennas like dipoles are common starting points. Size matters more at HF than at VHF, since wavelengths are longer. Radios range from small portable rigs to large base stations.
HF versus VHF and UHF
| Feature | HF | VHF/UHF |
|---|---|---|
| Typical range | Local to worldwide | Mostly line of sight |
| Antenna size | Larger | Smaller |
| Conditions | Vary with the ionosphere | Fairly stable |
| Typical license need | Class dependent | Often available to entry class |
Getting started
In the US, HF privileges for new Technician licensees are limited, so many people upgrade to General class for broader access. Look for a local radio club, talk to operators and listen on the bands before you buy equipment.