4 Metres

The 4-metre (70 MHz) band is an amateur radio band within the lower part of the very high frequency (VHF) band.

As only a few countries within and outside of Europe have allocated the band for amateur radio access, the availability of dedicated commercially manufactured equipment is limited. Most radio amateurs active on the band are interested in home construction or the modification of private mobile radio (PMR) equipment. As a result, communication on the 4-metre band tends to focus on technical topics, with long 'rag chews' being the norm as long as there is some local activity.

History

Historical Overview

The 4-meter band, occupying the 70 MHz frequency range, has been historically significant for various regional radio services. Post-World War II, the United Kingdom allocated a segment of the band, specifically 56-68 MHz, to British community radio stations, a provision that lasted until 1949. This allocation was subsequently reassigned for television broadcasting by the BBC. Later developments saw the band's usage extend to France until 1961.

The Radio Society of Great Britain (RSGB) was instrumental in advocating for the allocation of the 4-meter band to British community radio stations in 1956, replacing the 5-meter band. This reallocation provided a mere 200 kHz bandwidth initially, from 70.2–70.4 MHz. It wasn't until later years that the allocation expanded to the current standard of 500 kHz, ranging from 70.0–70.5 MHz.

International attention to the 4-meter band increased during the International Geophysical Year of 1957–1958, with several European countries being assigned frequencies within the 70 to 72.8 MHz spectrum.

International Frequency Allocations

During the 1990s, the European Radio Communications Office (now ECC) of the CEPT conducted a thorough spectrum analysis, which included the 4-meter band among other frequencies. The investigation's findings, published in 1995, recommended the consideration of the 70 MHz frequency as an amateur radio band, aligning with existing amateur radio service allocations.

For a detailed overview of country-specific allocations within the 4-meter band, refer to the comprehensive table updated regularly on the Four Metres Website (70MHz.org).

Expanding Access and Regulatory Developments

Several European and African nations have since broadened the 4-meter band's access to amateur radio operators. This shift from traditional commercial usage signifies the band's evolving role in radio communication. The CEPT has recognised the value of the 70 MHz band, leading to regulatory updates that support its use as a secondary amateur service.
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In March 1993 the European Radio Communications Office (now ECC) of the CEPT launched Phase II of a detailed spectrum investigation (DSI) covering the frequency range 29.7–960.0 MHz. The results were presented in March 1995. Regarding the Amateur Radio Service the DSI management team recommended (among other things) that 70 MHz be considered as an amateur band.

Allocations

The 4-meter band is gaining traction across various regions, with usage extending to amateur radio operators in Europe and Africa. Historically limited to the UK, Gibraltar, and British Military Bases in Cyprus, the band's allocation has evolved due to changes in technology and regulatory stances. The CEPT's recognition of the band for amateur radio use, facilitated by the regulatory footnote "ECA9," has been a significant factor in this growth. CEPT administrations may now authorise the band's usage between 69.9–70.5 MHz for amateur services on a secondary basis."CEPT ECC Recommendation (05)06," Electronic Communications Committee (ECC) within the European Conference of Postal and Telecommunications Administrations (CEPT)

Regular updates on the allocations are provided on the dedicated Four Metres Website (70MHz.org), reflecting the dynamic nature of frequency management."National Frequency Allocations," Four Metres Website (70MHz.org)

Propagation Characteristics

The propagation characteristics of the 4-meter band are influenced by its position adjacent to the 6-meter band. Propagation primarily occurs via the F2 layer of the ionosphere, similar to higher frequencies, and is augmented by sporadic E layers. The band also experiences unique conditions such as Aurora Borealis and meteor scatter effects, contributing to its versatility."Understanding Radio Wave Propagation," uthor's Name Journal of Radio Sciences

In Europe, sporadic E permits continent-wide communication, and while the band doesn't typically support the same propagation mechanisms seen in the 6-meter band, its higher frequency allows for more reliable contacts, particularly in northern latitudes."Propagation of Radio Waves," uthor's Name itle of the Publication/ref>

Propagation

The propagation characteristics of the 4-meter band are influenced by its position adjacent to the 6-meter band. Propagation primarily occurs via the F2 layer of the ionosphere, similar to higher frequencies, and is augmented by sporadic E layers. The band also experiences unique conditions such as Aurora Borealis and meteor scatter effects, contributing to its versatility.

In Europe, sporadic E permits continent-wide communication, and while the band doesn't typically support the same propagation mechanisms seen in the 6-meter band, its higher frequency allows for more reliable contacts, particularly in northern latitudes.

Equipment and power

Access to the 4-meter band is somewhat limited due to the scarcity of commercially produced transceivers specifically for this range. However, enthusiasts often utilise equipment that was originally designed for other purposes, modifying it to suit the 70 MHz band. For instance, devices like the Philips FM1000 and the Ascom SE550, while not expressly made for the 4-meter band, are popular among hobbyists for their adaptability and sufficient range for local communications.

Historically, there have been purpose-built amateur radio transceivers for the band, but these are less common today. Notably, some amateur radio operators have repurposed equipment to access the 4-meter frequencies, demonstrating the innovative spirit of the community.

Power Regulations

The power output of equipment used on the 4-meter band is subject to regulatory constraints to prevent interference with other services. Typically, radio enthusiasts adhere to the stipulated maximum power levels to maintain harmonious use of the spectrum. It's crucial that operators are familiar with and comply with their country's specific regulations regarding power limits for the 4-meter band."Modified Equipment for the 4-meter Band," uthor's Name itle of the Publication/ref>"Innovations in Amateur Radio Equipment," uthor's Name ournal Name/ref>"Regulatory Framework for the 70 MHz Band," egulatory Body ocument Title/ref>

Activity

United Kingdom

In the UK the band has a mix of AM, FM and DX activity, assisted by the recent support for 70 MHz in newer amateur radio equipment. In the UK, the band is also used for emergency communications, Internet Radio Linking Project links ( IRLP), data links and low powered remote control.

Ireland

There is considerable AM activity in the Dublin area. As band occupancy is relatively low, FM operation tends to take place on the 70.45 MHz calling frequency, and AM operation on the 70.26 MHz calling frequency.

Continental Europe

In Europe the band is still primarily used for more serious DX operation. Cross-band working between the 6-metre band or the 10-metre band is common to make contacts countries where the band is not allocated.

DX operation across Europe and beyond

During the European summer season, the band is frequently open for DX work across the continent, with the centre of activity for long-distance voice and digital/data communication situated in the lower part of the band. The compact size of both horizontal and vertical antennas designed for the 70 MHz band is beneficial to radio amateurs who enjoy DX work but have insufficient space for larger multi-element antennas designed for lower frequencies.

DX voice traffic in SSB mode can be found around the SSB calling frequency of 70.2 MHz, whereas AM/FM contacts tend can be initiated at the 70.26 MHz AM/FM centre of activity. When the band conditions are poor or in cases where stations operator are able to transmit with modest power levels only, modern digital modes, capable of decoding transmissions down to a -12 dB s/n level, such as PSK31, Thor or Olivia, still permit reliable keyboard-to-keyboard free text communications at relatively large distances. Other more resilient digital modes capable of decoding signal down to -20 dB s/n, such as FT8, JT9 and JT65, offer reliable signal report exchanges at distances of up to several hundred or several thousand kilometres, depending on band conditions.

Countries in which operation is permitted

Countries with a known band allocation:

*Bahrain (69.900–70.400 MHz)
*Belgium (69.950 MHz center frequency, 70.125–70.4125)
*Bosnia and Herzegovina (68–70.45 MHz)
*Bulgaria (70–70.5 MHz)
*Cayman Islands (69.900-70.300 MHz)
*Croatia (70.000–70.450 MHz)
*Czech Republic (70.100–70.300 MHz)
*Cyprus (69.900–70.500 MHz)
*Denmark (69.8875–70.0625, 70.0875–70.5125 MHz)BEK nr 1234 af 25/11/2024, retsinformation.dk, Bekendtgørelse om anvendelse af radiofrekvenser uden tilladelse samt om amatørradioprøver og kaldesignaler m.v.backup
/ref> (69.9 and 70.5 MHz used for/by repeaters)
*Estonia (70.000–70.300 MHz)
*Faroe Islands (69.950–70.500 MHz)
*Finland (70.000–70.300 MHz)
**Ã…land
*Germany (70.150-70.210 MHZ)
*Greece (70.000–70.250 MHz)
*Greenland (70.000–70.500 MHz)
*Hungary (70.000–70.500 MHz)
*Ireland (69.900–70.500 MHz)
*Israel (70.000-70.500 MHz)
*Latvia (70.000–70.500 MHz)
*Lithuania (70.240–70.250 MHz)
*Luxembourg (70.150–70.250 MHz)
*Malta (70.000–70.500 MHz)
*Monaco (70.000–70.500 MHz)
*Montenegro (70.050–70.450 MHz)
*Namibia (70.000–70.300 MHz)
*Netherlands (70.000–70.500 MHz)
*Norway (69.9–70.5 MHz)
*Poland (70.0–70.3 MHz)
*Portugal (70.1570–70.2125 and 70.2375–70.2875 MHz)
**Azores
**Madeira
*Romania (70.000–70.300 MHz)
* Serbia (69.900-70.500 MHz)
*Slovakia (70.000–70.500 MHz)
*Slovenia (70.000–70.450 MHz)
*Somalia (70.000–70.500 MHz)
*South Africa (70.000–70.500 MHz)
*Spain (70.150–70.250 MHz)
*Switzerland (70.0000 MHz-70.0375 MHz and 70.1125-70.5000 MHz)
*United Arab Emirates (70.000–70.500 MHz)
*United Kingdom (70.000–70.500 MHz)
**Gibraltar
**Guernsey
**Isle of Man
**Jersey
**St. Helena
**Falklands

Countries with past or current experimental operation

In "experimental" countries, authorities authorised amateur radio experiments on the band for a limited period of time.

*Germany 2007-2010 (69.950 MHz center frequency) under a special ("DI2xx") licence.
For class "A" operators in 2014, 70.000-70.030 MHz, and in 2015, 2017, & 2018, 70.150-70.180 MHz were allocated under specific restrictions (25 W ERP, Horiz. polarisation, 12 kHz maximum bandwidth, no portable operation, non interference basis, all transmissions to be logged with frequency, antenna direction, date/time, call signs) for four months, Starting May 2 and ending at the end of August each year (effectively for the sporadic-E season).

On December 19, 2018, BNetzA (the German regulator) published announcement 414/2018 issuing immediate access to 70.150-70.200 MHz for German class "A" (full) licencees up until December 31, 2019, with the same rules as shown above.
* Sovereign UK bases in Cyprus (70.000–70.500 MHz)
*An automatic beacon has also been authorised in Austria, Cyprus, and Hungary
*North Macedonia 70.000 MHz, 70.075 MHz, 70.125 MHz and 70.275 MHz Starting in May 2019, N. Macedonia amateurs may apply for a one-year experimental permit granting access to 4 meters.
*Italy (70.0875–70.1125, 70.1875–70.2125, and 70.2875–70.3125 MHz) only on temporary basis during 2007-2008-2010-2012-2014-2023 (August 6-December 31), also 70.3875-704125 MHz in 2024 (August 30-December 31)
*Bonaire 70.000-70.500 MHz on a temporary basis from December 2022 until December 2023, might be renewed.
*Sweden 70.125-70.150 MHz authorised only for a few stations with special permits (status 9/2024)

Others

* United States has one experimental transmitter, station WE9XFT in Virginia, transmitting CW on 70.005 MHz. The beacon continues to be operated under the Experimental radio service call sign WG2XPN and is active as of March 2021.
* A petition was filed with the U.S. Federal Communications Commission on 27 January 2010 to create a new U.S. 4-meter amateur radio allocation at 70 MHz to parallel those in Europe and other parts of the world. This petition was subsequently rejected by the FCC.

Common uses of the 4-metre band

* FM simplex
* AM simplex
* Packet radio
* SSB voice operation
* Morse code ( CW) operation
* DX

References

External links

*
* – was "DX-Sherlock's real-time 4 m propagation maps", prior to a domain merger.
* – was "DX-Sherlock's real-time VHF&up propagation ticker", prior to a domain merger.

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Amateur radio bands