A World of Radio Frequency
A Brief History of Radio Frequency
Since it's infancy, the use of radio has been subject to extensive controls. These controls often fall at the feet of Government agencies, who are responsible for sanctioning these frequencies. These controls include:
- Frequencies which can be used
- Who can use the different frequencies
- The duration a frequency can be used
- Where a frequency can be used
In the early days radio regulatory powers were generally vested in the postal authorities. This caused a strong conflict of interest, as the same authorities ran the rapidly growing telecommunications systems, and there was fear that the success of radio would damage the revenue of the telephone industry. In more recent times however, this has not proven to be the case. The various regulatory bodies now act as a means of allocating precious frequencies to the many and varied applications to which radio is put.
The regulations and controls are necessary for radio to work. If you didn't ensure there were harmonic frequencies then items could be transmitted, on not only the frequency you require but also various other ones. This would not only lower the chance of your transmission being received by the intended receiver, but your signal could also be blocked from other transmission's in the area or received by an unintended recipient.
Monitoring Radio Worldwide
Radio frequencies are used worldwide by different organisations, for a range of different reasons; television stations, emergency services and car manufacturers to name a few. Each different licensed frequency is allocated to company / service and can only be used by them. The allocation of frequencies is carried out on a worldwide basis by the 'International Telecommunications Unions - Radio' (gernally referred to as the ITU-R).
In addition to allocating frequencies, the regulatory bodies have the task of ensuring that a transmitter being used in one band does not interfere with one being used in another. Such problems would render the use of radio unworkable in many applications.
Radio for the Masses
License free frequencies are availalbe to be used by anbody withing to use them, the most commonly known include; 315MHz, 433MHz, 868MHz, 915MHz and 2.4GHz. Though they are 'unlicensed' there are still regulations which must be abided by. Restraints include; where they can be used and how long you can transmit for to help prevent cuasing interference.
Here in the UK we are able to use 433MHz and 868MHz bands. It is very important to bear in mind that every country or region has specific frequencies they can use and its own set of rules when using radio.
Available Unlicensed Frequency Bands
|Country / Region||Frequency|
|315MHz||U.S. and Asia|
|433MHz||Europe, Asia, Australia, U.S. (limited)|
|915MHz||U.S. and Australia|
Designing with Radio
When a Designer is working with radio and developing a new product, frequency is going to be one of the biggest decisions that need to be made. The frequency the Designer chooses will dictate where the product can be used, where the product can be sold and the performance of the product.
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Please don't make the common mistake, there is NO such thing as unlicensed spectrum in the UK. Bands like 433MHz, 868MHz, 2.4GHz are license exempt. This means if you stick to the license published by Ofcom (in a Standard Instrument - i.e. an Act of Parliament), you don't need a specific license (which you would be very unlikely to get in license except bands).
Generally the SI contains a list of technical requirements such as channel size, max power (ERP or EIRP) etc. Also the requirement may be that all equipment is CE marked. There are variances for running tech trials (such as in 868MHz, however systems must not be more than 300m apart). It is possible to get a test license from Ofcom to do more realistic testing in real world environments and these cost around £50 (maybe per piece of equipment).
Non compliance is a criminal offence and Ofcom can prosecute (usually when something is interfering with some other user) and the Wireless Telegraphy Act is hugely punitive compared to the offence.