The 6 m band
and the 4 m band

These two frequency ranges, which are currently released for use by amateur radio due to special temporary regulations, are located between the shortwave range extending to 30 MHz and the 10-m band, respectively, and the VHF range.

Not only do the 6 m and 4 m bands have a special legal status, but their propagation conditions also differ from those of other frequency ranges. These special features will be briefly described here. Of course, hints for suitable equipment will not be neglected!

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FAQ

Which antennas are suitable for the 6m/4m band?
Yagi antennas or omnidirectional antennas are particularly suitable for the 6m/4m band. These antennas are tuned to the corresponding frequency and offer good reception and transmission performance.
How big should the antenna be for the 6m/4m band?
The size of the antenna depends on the design chosen. A Yagi antenna has several elements mounted on a carrier, making it larger than an omnidirectional antenna. In general, however, the larger the antenna, the better the reception and transmission performance.
How many watts should the antenna system for the 6m/4m band have?
The required power of the antenna system depends on various factors, such as the distance to the receiver or the desired transmission behaviour. In general, however, antenna systems with a power of 50 watts to 100 watts are sufficient for the 6m/4m band.

Propagation: ground wave, ionosphere, and sporadic E layer.

If you "just happen" to shoot over frequencies between 50 MHz and 52 MHz, you will often not notice any signals. This is even more true for the 4 m amateur band. The physical reason is the mixture of shortwave and typical VHF characteristics. To bridge distances exceeding the range of the ground wave, which is subject to the conditions of quasi-optical propagation, special propagation conditions are required.

The good news is that if suitable conditions prevail, distances many times the normal range can be bridged with low power. For this reason, the 6-m range is called "the magic band." The same applies to the 4-m band, although the requirements for propagation conditions are even higher due to the higher frequency. The decisive factor is the reflectivity of the ionosphere. The measure of all things is the maximum usable frequency (MUF). This value, which depends on the geomagnetic solar activity, must be at least as high as the frequency range to be used. Reflections over the ionosphere are possible, both over the E-layer and the F-layer, but here almost exclusively in the sunspot maximum. The next one is expected for the year 2025, so these are currently the best conditions to use the bands!

Radiation of a ground wave close to the surface and a space wave reflected at the ionosphere Radiation of a ground wave close to the surface and a space wave reflected at the ionosphere

The distances that can be bridged depend on the layer of the ionosphere in which reflections occur. The higher the reflective layer, the greater the theoretically possible range of the radio signal. However, the area-wide receivability of a certain signal is an exception: spatially strongly varying signal strengths are typical. Reception in "local transmitter quality" may well prove to be non-reproducible in the neighboring village. Connections over the sporadic E-layer occur in the northern hemisphere preferably during the day in the months May to July. A high ionization of the ionosphere at the height of the E-layer causes a reflection of waves which otherwise would not be reflected or would be reflected by a higher ionospheric layer. Normally, connections with hop distances of up to 1500 km occur over this layer. Tropospheric overreach is caused by inversion weather conditions: Cold air below and warm air above create "waveguides", which lead to overreach distances of 300 to 400 km in case of a ground-level inversion. If the inversion exists in higher layers, distances of up to about 1000 km can be bridged. These conditions are often relatively stable for hours.

Radiation of a ground wave close to the surface and a space wave reflected at the ionosphere Radiation of a ground wave close to the surface and a space wave reflected at the ionosphere

Ionospheric layers depending on the time of day: At night the E-layer and the F-layer are active. During the day, the D-layer is formed by the sun; the E- and F-layers are more pronounced. Two F-layers often form throughout the day: The lower F1 layer ranges from 150 to 220 km altitude. Above the F1 layer, the F2 layer spreads out between 220 and 800 km altitude.

Radiation pattern of a sporadic E event. Shortwave radiations above the normal E-layer MUF (red) pass through the E-layer. However, during a sporadic E event, the signals (blue) are completely or partially refracted in the E layer, resulting in a reduced propagation distance, but also in an enhancement of reception in the first-hop zone (dead zone). Radiation pattern of a sporadic E event. Shortwave radiations above the normal E-layer MUF (red) pass through the E-layer. However, during a sporadic E event, the signals (blue) are completely or partially refracted in the E layer, resulting in a reduced propagation distance, but also in an enhancement of reception in the first-hop zone (dead zone).
Representation of reception messages of European radio amateurs in February 2023 in the 6 m band Representation of reception messages of European radio amateurs in February 2023 in the 6 m band

Propagation via the F2 layer is the supreme discipline; transcontinental links are possible via this layer. Propagation relies on daylight links, although in exceptional cases long-distance links have been achieved hours after local sunset. Often these radio links are limited to certain directions, which may also change over time. Nothing is predictable, but persistent monitoring of the bands - in the presence of a MUF above 50 MHz or 70 MHz - is a sensible course of action. The frequency of band openings in the 4 m range is lower compared to 6 m, which increases the challenge. A viable overview for both bands is provided by DX Maps' world map displays, which graphically depict current reception messages in real time. Both the section and the frequency range are preselectable:

dxmaps.com
wave-02 wave-02

Operating technology: useful life, information exchange and frequencies for FT8

Since the appeal of these bands lies more in the use of unusual propagation conditions whose useful life can never be precisely determined, there are no long "chats" or rounds of several radio amateurs in either SSB or CW. Rather, it is customary to limit the exchange of information to what is necessary to make a large number of connections possible. In the 6-m band, beacons can be used that broadcast their CW identifier in the 50 MHz to 50.5 MHz range to help assess propagation conditions.

The popular FT8 transmission mode is in the 6-m band on the standard frequency 50.313 MHz. The DX frequency 50.323 MHz should be reserved for intercontinental connections. Europeans transmit on the latter frequency at the even seconds, i.e. :00 and :30.

In the 4 m band there is no separate DX frequency for FT8, here 70.154 MHz should be used.

Equipment: transceivers, antennas and transmission types

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transceiver

Current amateur radio transceivers, which only receive the 4 m and 6 m band - ICOM IC-7300 or Yaesu FT-710 for example - can often be modified to transmit in these bands. Please contact us!

Other station devices
Antennas

When choosing an antenna, please note that in Germany only antennas with horizontal polarization meet the legal requirements. Please note the legal requirements for your country. We offer a wide range for both frequency bands.

4 M BAND

Antennas at WiMo

6 M BAND

Antennas at WiMo

Wimo Rotors Wimo Rotors
Rotor

Directional antennas provide the highest gain in the direction of radiation, but a rotor is essential to make the best use of the particular propagation conditions.

Rotors im WiMo-Shop
Round beam

Provided the band is open, interesting long-range links are also possible with omnidirectional antennas. We offer horizontally polarized antennas with omnidirectional characteristics that comply with the legal requirement. Advantage of these antennas: Receptions from all directions are equally covered. Another option is the Delta 11 loop antenna for 20 m to 6 m. As a bidirectional antenna, it covers two directions simultaneously. A rotor is recommended.

VGR Antenna
VGR Antenna
Big Wheel Antenna
Big Wheel Antenna
Eantenna Delta11
EAntenna DELTA11

Transmission modes used: Weak Signal Modes, CW and Meteor Scatter

A majority of connections today take place in what are known as weak signal modes. These are digital transmit modes designed for use in difficult conditions and allow decoding below the noise floor.

For unstable connections that last only for a few seconds at a time, CW is the transmission mode of choice. Here QSOs are possible whose duration is significantly less than that of a connection in FT8 mode.

Meteorscatter is in principle feasible and the reflections also last sufficiently long, but in practice most operation takes place on the 2 m band. Earth-Moon-Earth (EME) connections are made, but these are rather exceptions because of the antenna effort: Antenna dimensions in the 6-m band are three times those of 2-m antennas.

Wave 02 Wave 02

Band plans

Legal regulations in Germany

Notice: The following paragraph refers to the legal situation in Germany. Other countries certainly have different rules and laws. We ask you to familiarize yourself with the local regulations in good time before setting up an antenna system. Thank you.

Effective 5/6/2020, holders of a license to participate in the Class A and Class E Amateur Radio Service may use the 6-m band under the following conditions:

  • 50.000 ... 50.400 MHz with 750 W transmit power PEP for Class A or 100 W for Class E.
  • 50.400 ... 52.000 MHz with 25 W transmission power PEP for classes A and E
  • in each case in all transmission modes with ≤ 12 kHz maximum bandwidth
  • in each case with horizontal antenna polarization

In addition, contest operation is expressly permitted, but use is still restricted to fixed amateur radio stations. Until further notice, the submission of an operating report for the use of the 50 MHz frequency range and the availability of the amateur radio station by telephone at any time during transmission operation is waived.

Logbook keeping including date, time, frequency, modulation type, transmitting power and, if applicable, call sign of the remote station is still mandatory.

Other radio services and telecommunications equipment, including wire-bound broadcast transmissions, must not be disturbed. In the event of interference, the radio amateur must immediately stop the interfering transmission. Interference from other radio services and telecommunications equipment must be accepted.

For radio operation on the 4 m band, in the frequency range 70.150 - 70.210 MHz applies:

  • 25 W transmitting power ERP.
  • Use is restricted to fixed amateur radio stations and may be performed only by holders of a license to participate in the Class A amateur radio service.
  • in each case in all transmission modes with ≤ 12 kHz maximum bandwidth.
  • in each case with horizontal antenna polarization

These toleration regulations have been valid for one year at a time since 2020. The 14-daily official gazettes of the Federal Network Agency provide information on the regulations:

Legal regulations in other countries

The regulations in the Western European countries regarding the frequency ranges released for amateur radio and their use may differ despite harmonized provisions. Also due to their time limits, it is recommended to obtain information from the websites of the respective telecommunications authorities and amateur radio associations.

At the time of this compilation, the following information is available:

Regulations for Austria

The maximum allowed transmit power in Austria is 100 W; mobile operation is also allowed. The restriction on the operating mode has been lifted and unmanned transmitters (repeaters, beacons and digipeaters) have also been permitted. A maximum radiated power of 10 watts ERP applies here. Amateur radio has a secondary status here: in the event of interference, the radio amateur must immediately stop the interfering transmission. Interference from other radio services and telecommunications equipment must be accepted.

Regulations for Switzerland

National frequency allocation plan for Switzerland

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