About Licence-Free RF Bands

2019-02-14 10:43:15 Admin 19

There are several forms of unlicensed two way communications systems or personal radio services that are available in different countries. These unlicensed communication systems take different forms and are available in different countries.

 

SRD860 – 869 License free radio operation

In Europe, 863 to 870MHz band has been allocated for license free radio operation using FHSS, DSSS, or analog modulation with either a transmission duty cycle of 0.1%, 1% or 10% depending on the band.

 

Short-range devices are low-power transmitters typically limited to 25–100mW effective radiated power (ERP) or less, depending on the frequency band, which limits their useful range to few hundred meters, and do not require a license from its user.

 

Applications for short-range wireless devices include power meters and other remote instrumentation, RFID applications, radio-controlled models, fire, security and social alarms, vehicle radars, wireless microphones and earphones, traffic signs and signals (including control signals), remote garage door openers and car keys, barcode readers, motion detection, and many others.

The European Commission mandates through CEPT and ETSI the allocation of several device bands such as the Pan-European license free 869MHz band for these purposes. The Output Power and Duty Cycle restricts the parameters of their use, and provides guidelines for avoiding radio interference.

 

900MHz band license free radio

The 33-centimeter or 900MHz band is a portion of the UHF radio spectrum internationally allocated to amateur radio on a secondary basis. It ranges from 902 to 928 MHz and is unique to ITU Region 2. The International Telecommunication Union (ITU), in its International Radio Regulations, divides the world into three ITU regions for the purposes of managing the global radio spectrum. Region 2 covers the Americas, Greenland and some of the eastern Pacific Islands.

It is primarily used for very local communications as opposed to bands lower in frequency. However, very high antennas with high gain have shown 33 centimeters can provide good long range communications almost equal to systems on lower frequencies such as the 70 centimeter band. The 70 centimeter band is the 430.000 – 440.000MHz UHF band.

 

2400MHz ISM license free radio

The industrial, scientific and medical (ISM) radio bands are radio bands (portions of the radio spectrum) reserved internationally for the use of radio frequency (RF) energy for industrial, scientific and medical purposes other than telecommunications. In recent years the fastest-growing uses of these bands have been for short-range, low power communications systems. Radio frequencies in the ISM bands have been used for communication purposes, although such devices may experience interference from non-communication sources.

 

In recent years ISM bands have also been shared with (non-ISM) license free radio error-tolerant communications applications.

 

Citizens’ Band, CB: Citizens’ Band, CB is strictly not an unlicensed system as Licenses are often required, but they are very easy to obtain, requiring very little administration. The frequencies used are around 27MHz which can enable worldwide communication to be established and hence high levels of interference may be experienced.  

 

PMR446: PMR446 (personal mobile radio, 446MHz) uses a band in the UHF portion of the frequency spectrum. It is open to use without any form of License for business and personal use and it is available in most countries of the European Union, and some beyond.  

 

FRS, Family Radio Service: The Family Radio Service (FRS) is a walkie-talkie based radio system authorized in the United States since 1996. It is available in the USA, Canada, Mexico and several South American countries. Using the UHF portion of the radio spectrum it avoids the high levels of interference and misuse seen on CB.  

 

GMRS: The General Mobile Radio Service, GMRS, is a land-mobile FM UHF radio service designed for short-distance two-way communication. It requires a License in United States but some GMRS compatible radios can be used License-free in Canada.

Both PMR446 and FRS require that type approved radios are used. These are typically small handheld walkie talkies that have limited range. Also they must not use detachable antennas and this further limits their range over that which might be achievable when large antennas are used. However it means that interference is limited and enables the systems to operate with minimal interference and misuse.

 

About License-free (PMR446) radios

Radio transmitters, including two way radios, and the VHF or UHF frequencies they operate on, are governed, licensed and co-ordinated by OFCOM in the UK. Two way radios can operate on either licensed or License-free (PMR446) frequencies. Here we explain more about License-free radios.

  • License-free radios are generally lower powered, handheld radios witha maximum power output of 0.5 watts, resulting in a shorter range.

  • Depending on the surrounding terrain, the range can vary from afew hundred metres in a built up area to a few kilometres in open ground.

  • Use License-free radios for business or personal use on any ofeight UHF frequencies, both in the UK and across the European Union.

  • PMR stands for Personal Mobile Radio

  • 446 refers to the UHF frequency range 446MHz on which License-freeradios are permitted to operate.

  • In the USA and Canada the closest equivalent to PMR446 is FRS or GMRS


License-free two way radios are manufactured with the frequencies already programmed in. Power sources can vary, from basic models which use AA cells to more advanced models which use Li-ion rechargeable packs.


The actual PMR446 frequencies

For those of you who want to get right down to the nitty gritty, here are the actual eight PMR 446 frequencies in the UK which are used for License-free radios.

446.00625 MHz

446.01875 MHz

446.03125 MHz

446.04375 MHz

446.05625 MHz

446.06875 MHz

446.08125 MHz

446.09375 MHz