The following guidance notes have been prepared with the help of ASP Frequency Management Ltd. (who handle radio microphone licensing on behalf of the DTI) and Sennheiser UK Ltd. Radio microphones and their usage falls into three groups, for each of which differing approvals and frequencies apply.

Deregulated devices

These must be type approved to DTI specification MPT 1311 or MPT 1345 and must work on the following frequencies only (max. erp 2 mW). These devices may be used anywhere within the UK without a license.

173.800MHz
174.100MHz
174.500MHz
174.800MHz
175.000MHz

Indoor fixed site radio microphones for theatres, conference halls, churches etc.

Almost 40 frequencies are available, dependant on geographical location (more frequencies are available in London, for example, than in many other areas). Radio microphones in this group may transmit at higher power levels than de-regulated devices. The limit is 10mW erp for hand-held devices and 50mW erp for pocket transmitters. They must be type-approved to MPT 1350 specification.

VHF frequencies available

In the band 173.7MHz - 175.1MHz, plus two fixed frequencies of 176.4MHz and 177.0MHz. (In practice this gives a total of 6 usable frequencies).

UHF frequencies available

For London use only: up to 12 fixed frequencies in TV Channels 22,24 and 25.

For use in London, Birmingham and in areas where the new TV Channel 5 is not broadcasting on these frequencies: TV Channel 35 within the limits 583.355 to 586.835MHz and 588.300 to 589.250MHz. (In practice this gives a total of 8 to 10 usable frequencies).

Whole country: TV Channel 69 within the limits 856.100 to 859.650 MHz.

Licenses are required for these fixed site frequencies currently costing £135 per site (£225 if both Channel 35 and 69 frequencies are used) available from ASP.

UK general radio microphones

There are various VHF and UHF frequencies available for general UK use both for outdoor and indoor use. Radio microphones are of the same higher power type as used for indoor fixed site use above and must be type-approved to MPT 1350.

Licenses are required for these frequencies currently costing £100 per frequency per year available from ASP.

Multi-Channel Systems

To avoid any inter-modulation problems when installing more than once receiver, or if further receivers are added at a later date, great care must be taken with choices of frequencies.

If a de-regulated system is envisaged then 174.8MHz should be avoided. 174.1MHz should also be avoided for Beyer and Trantec systems, but this frequency is usable if a Sennheiser or EDC system is planned, due to the substantially more refined circuitry afforded by the higher price level.

If only a single channel use is envisaged there is no problem in using 174.100MHz or 174.800MHz frequencies. For a four channel system, the best choice of frequencies would be: 173.800, 174.500, 175.000 and 177.000MHz.

However, if the frequency 177.000MHz is used, a license must be obtained for its legal operation, and units need to be approved to MPT 1350. This frequency is only licensable for indoor use.

If fixed site frequencies are envisaged please contact us for advice, as intermodulation free frequencies vary with each manufacturer. If a licensed UK general system is envisaged all ten frequencies above are intermodulation free and can be used together.

For licensing queries please contact ASP. For other queries please contact us and we will be happy to help in system planning.