Wireless Microphone Frequencies
VHF (Very High Frequency) wireless microphones operate within the range 173 - 175MHz, and these are freely available for the public to use without a licence. They are usually at the cheaper end of the scale, and can be more prone to interference. You can only use four wireless VHF microphones in the same place at the same time because the available bandwidth is so narrow. e.g. you can use four of these systems (on different frequencies) at the same time QTX VH1 wireless system
UHF (Ultra High Frequency) microphones operate on wider bandwidths than VHF, some of which can only be used legally under licence from Ofcom.
- Channel 69 (854 - 862 MHz) became illegal to use in the UK at the end of Dec 2012. Ofcom sold off this bandwidth to the mobile phone 4G networks. If you have an old system operating on this range you will probably find it's not giving good results, and this is why.
- Channel 70 (863-865 MHz) is free for the public to use, you do not need a license. You can only use four wireless Channel 70 microphones at the most in the same place at the same time because the available bandwidth is narrow. E.g. you can use two of these dual systems at the same time Chord NU2 wireless system.
- Channel 38 (606.6 - 613.5 MHz) is a wider bandwidth and you can use many wireless microphones at the same time within this range. You will need a licence from Ofcom to operate them, however. Licences are available from £28 per microphone per year. E.g. Trantec Racked'n'Ready systems
- 624-697 MHz microphones are also very popular, and you can use many wireless microphones together within this range. Again, you will need a licence from Ofcom to operate them. Licences are available from £28 per microphone per year. e.g. IMG Stageline TXS-646 wireless system
Pre-set frequencies or changeable?Some wireless systems are pre-set to fixed frequencies that you cannot change. VHF tend to be pre-set. Some UHF are pre-set and some are changeable, allowing you to select your frequencies within a range. This is useful because you'll find that some frequencies work better than others in your area. If a frequency doesn't work well or has a lot of interference it can dropout, sound crackly, or even sound like it's underwater! Change a few MHz and it will be as clear as anything.
True Diversity means is that the transmitter sends two signals to the receiver on different frequencies which are then summed at the receiver end. This reduces the amount of drop-out or signal loss. If you have a wireless system that is not true diversity it could be prone to drop out.
Ofcom control the licensing of wireless microphones and monitors. Their website is very confusing and it's sometimes easier just to call them! However, please click here for more information on the types of licences available on the Ofcom website, and please click here for details of Ofcom fees for Shared Licences and Fixed Site licences.
As at Sept 2018, it's £28 per year for a fixed site indoor licence and £75 per year for a shared licence covering up to 10 microphones.
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