630 Meter and 2200 Meter Bands: Amateur LF and MF Guide
Most hams think the 160 metre band is as low as the hobby goes. It is not. Two more bands lie below it, in the medium and low frequency parts of the spectrum, with wavelengths of hundreds and thousands of metres. The 630 meter band and the 2200 meter band are the quiet frontier of amateur radio: tiny power limits, huge antennas compared with the power they radiate, and a community of experimenters who work stations across oceans with a fraction of a watt.
This guide explains where the two bands are, who may use them and at what power, how signals travel on them, what equipment and antennas operators use and what you should consider before you build a station. Facts about allocations and propagation come from published encyclopedia articles, which are linked in the text. Rules differ from country to country and change over time, so always check your own regulator.
Where the Bands Are
The 630 meter band, also called the 600 metre band, covers 472 to 479 kHz, or wavelengths of about 626 to 635 metres. It was formally allocated to amateurs at the 2012 World Radiocommunication Conference. The band sits in the medium frequency region, within the old 415 to 526.5 kHz maritime band, and the allocation is secondary in all ITU regions.
The 2200 meter band covers 135.7 to 137.8 kHz and is the lowest band in which amateurs are licensed to transmit. It was allocated at the 2007 conference, again on a secondary basis, and lies within the low frequency region just below the longwave broadcast band. The allocation requires care: the same article notes that the band 130 to 148.5 kHz is otherwise allocated on a primary basis to maritime mobile and fixed services, with naval one-way transmissions and radiolocation systems among the main users.
| Band | Frequency range | Region of spectrum | Allocated | Power limit in the ITU allocation |
|---|---|---|---|---|
| 2200 m | 135.7-137.8 kHz | Low frequency (LF) | WRC-07 (2007) | 1 W EIRP, secondary |
| 630 m | 472-479 kHz | Medium frequency (MF) | WRC-12 (2012) | 1 W EIRP, secondary; 5 W allowed far from certain countries |
Rules, Power and Coordination
The power limit is expressed as effective isotropic radiated power, not transmitter output. National rules vary. The 630 metre article lists, for example, 5 watts EIRP in Australia, Belgium, Canada and the United States, 1 watt in France, Norway and Poland and 25 watts in New Zealand. In the United States, the article says, amateurs must notify the Utilities Technology Council and keep at least 1 km from power transmission lines carrying power-line communication signals on the same frequencies. The 2200 metre article describes the same notification process, with operations allowed to begin after 30 days unless the council reports that your antenna is within a kilometre of such systems. The article also mentions that a list of countries, including several in Europe, North Africa and the Middle East, prohibits amateur operation in the 630 metre band. The 2200 metre list of countries with a known allocation includes Lithuania.
The lesson is simple: do not assume that your friend’s rules apply to you. Find your regulator’s table, note whether the band is open to your licence class, check the power limit in EIRP or ERP, and see whether you must coordinate with anyone. Also be careful about the phrase power limit. Getting even 1 watt radiated can be difficult on these bands, and being at the legal limit is rarely the problem.
How Signals Travel on LF and MF
The encyclopedia article on low frequency explains that the main mode of propagation in the LF band is the ground wave, in which radio waves travel just above the surface of the Earth following the terrain and can diffract over hills and beyond the horizon. Signal strength falls off exponentially with distance because the ground absorbs energy, but the loss is lower than at higher frequencies, and ground waves can be received up to 2,000 kilometres from the transmitter. The same article points out that ground waves must be vertically polarized, which is why vertical monopoles are used for transmitting. That is why low-frequency work is largely a vertical antenna game. Skywave propagation also occurs, by refraction from the E or F layer, but it is less common than at higher frequencies, with detected signals beyond 3,000 kilometres.
The article on medium frequency describes the daily pattern that matters for the 630 metre band. Ground waves cover a radius of several hundred kilometres. The ionospheric D layer, which absorbs MF waves, is heavily ionised during the day, in summer and at times of high solar activity. At night, especially in winter and at solar minimum, the D layer can virtually disappear, and MF signals refracted by the F layer can be received hundreds or even thousands of miles away. For the operator, that means winter nights are the season of 630 metre DX.
The record on 2200 metres shows what is possible: the low frequency article reports a world record two-way distance of over 10,000 kilometres, from near Vladivostok to New Zealand. Our guide to 160 metre DXing covers the nearby band that shares many of the same seasonal patterns.
Noise: The Real Limit
Atmospheric radio noise increases as frequency falls, according to the LF article. At LF and below, the noise is far above the thermal noise floor of a receiver, so a weak signal can be amplified without a perceptible increase in noise. As a result, even inefficient receiving antennas much smaller than the wavelength can work well for reception. This is a useful fact: you do not need a huge antenna to hear stations on LF, and a small loop or a short whip can do the job. The problem is man-made noise. Switching power supplies, lighting dimmers, electric fences and neighbours’ equipment can drown out signals. If you plan to try the bands, start by listening and learning how quiet your location is, and read our guide on finding and killing RF noise at home. Receive antennas that reject local noise can make a large difference, and our article on low band receive antennas covers the principles, although LF calls for much smaller solutions.
Modes: Why Everything Is Slow
The 2200 metre article states that many users and experimenters have settled on extremely slow, computer-generated and displayed Morse code, known as QRSS, with the doubled S emphasising the slowness, as the most common mode. Slow signals, read from a spectrogram, make it possible to detect transmissions that would be inaudible at normal speed. Narrow bandwidth is the key to weak-signal performance everywhere, and on LF the low radiated power makes it essential. The IARU Region 1 band plan from 2005, as quoted in the article, divides 2200 metres into a test and transatlantic window at the bottom, a telegraphy section, a digital modes section and a very slow telegraphy segment centred on 137.7 kHz.
On 630 metres, operators use conventional CW as well as digital modes. The 630 metre article reports that amateurs have experimented with weak-signal communication near 474.2 kHz using WSPR, and that in the United States CW, RTTY, data, phone and image emissions are allowed. Some countries restrict modes, for example the Netherlands, where only certain telegraphy and data emissions are listed and contests are not permitted. Again, check your own rules before choosing a mode.
Antennas and Ground
The physics is unforgiving. A quarter wavelength at 136 kHz is roughly 550 metres and at 475 kHz roughly 160 metres, so every practical amateur antenna is electrically very short. The usual solution, used for generations on the longwave and medium wave bands, is a vertical monopole loaded with a coil to bring it to resonance and a top hat of wires to increase its capacitance, working against an extensive ground system. Because the radiation resistance of such an antenna is tiny, most of the transmitter power can be lost in the ground and the loading coil. Efficiency is often a few percent at best, which is why the 2200 metre article notes that even 1 watt radiated can be extremely difficult to achieve from practical equipment and antennas. Many operators use a long wire or a tall mast as a top-loaded vertical, an inverted L, or an existing tower fed against the ground, as long as it is safe.
Good grounding is as important as the antenna itself. A buried radial system or an extensive earth connection reduces losses, and a wet, conductive soil helps. Safety matters too: the high voltages at the end of a short, high-Q antenna can be hazardous. Read our articles on station grounding and lightning protection before you start.
Transmitters and Receivers
Mainstream HF transceivers usually do not cover these bands, so most stations rely on specialised equipment. The 2200 metre article says that such low frequency transmissions require specialised, usually custom-made equipment. That is part of the appeal: many operators build their own transmitters, amplifiers and matching networks, or modify other gear. For reception, many use a general-coverage receiver or a software-defined radio with a suitable antenna and a computer to display a spectrogram.
Who Else Is on the Frequencies Nearby
These bands are neighbours to services that do not tolerate interference. The medium frequency article notes that non-directional navigational beacons occupy 190 to 435 kHz, that the old 500 kHz maritime distress frequency was kept for many years, that Navtex broadcasts important digital text on 518 and 490 kHz, and that the 630 metre allocation lies inside the maritime band. In Europe, the longwave broadcast band between 148.5 and 283.5 kHz lies just above the 2200 metre band, and time signal stations also use the low frequency range. The 2200 metre band is itself shared with naval and radiolocation users, and in the United States power-line carrier systems are a concern, which is why the coordination process exists. As a secondary user you must accept interference from them and must not cause any, so keep your power modest, stay within the band edges and never assume that a quiet frequency is unused.
Getting Started
- Check the rules. Confirm that the band is allocated in your country, find the power limit and the licence class required, and find out about coordination.
- Listen first. Use a receiver and a small antenna to hear beacons, time signals and other amateurs. You will learn a lot about noise at your site.
- Join a community. Experimenters share designs, schedules and results, and many are glad to help newcomers.
- Plan the antenna. Decide whether you can erect a tall top-loaded vertical, and design the ground system before the antenna.
- Start with a beacon or a slow mode. A low-power beacon with QRSS or WSPR is a good way to see how far your signal goes.
- Be careful with RF safety and interference. Keep within your limit and avoid interfering with the primary services on adjacent frequencies.
The Bottom Line
The 630 meter band and the 2200 meter band are not for people who want quick contacts and big signals. They reward patience, careful construction, an understanding of ground wave propagation and a taste for slow modes. Allocations and power limits vary, noise is the main enemy and antennas are always a compromise, but the results, including contacts over thousands of kilometres on a fraction of a watt, are among the most satisfying in the hobby. Read the rules, listen, build carefully and share your results.
Frequently Asked Questions
What frequencies are the 630 and 2200 meter bands?
The 630 meter band is 472 to 479 kHz, and the 2200 meter band is 135.7 to 137.8 kHz. Both are secondary allocations to the amateur service in the ITU Radio Regulations.
How much power can I use?
The ITU allocations set a limit of 1 watt EIRP, with 5 watts allowed on 630 metres in some circumstances. National rules differ, so check your own regulator.
Can I use ordinary SSB on these bands?
That depends on your country. In some places phone is allowed on 630 metres, but most activity uses CW, QRSS and narrow digital modes because of the low power and high noise.
How do signals travel on the 2200 meter band?
Mainly as vertically polarized ground waves that follow the Earth’s surface, which can reach up to about 2,000 kilometres. Skywave contacts over longer distances also occur.
What is QRSS?
It stands for extremely slow, computer-generated Morse code displayed as a spectrogram. Its narrow bandwidth lets operators detect very weak signals.
Do I need a large antenna to hear stations?
No. Atmospheric noise is high on LF, so small receiving antennas are usually adequate. Transmitting efficiently is the hard part.