Q - What have your wireless microphones to do with Digital TV?

A - They share the same UHF broadcast frequency spectrum.

For some years now, the introduction of digital terrestrial television (DTTV), also called DVB-T (Digital Video Broadcast - Terrestrial) in Europe, or Freeview in the UK, has been progressing rapidly.

The problem

DVB-T is an international transmission standard for terrestrial digital television. Digital TV signals are transmitted in the same frequency range as their analog predecessors were. This is also the frequency range used for UHF wireless microphones.

In the UK, an analogue television channel only uses 7 MHz of the 8 MHz wide UHF channel. Until now, the remaining 1 MHz gap has been used for communication, reporting transmitters and to some extent for wireless microphones.

Digital television, however, completely occupies the 8 MHz wide channel. Due to the form of the new digital signal that DVB-T uses, the 1 MHz gap is no longer available.

The situation is complicated because the UHF TV spectrum runs from 470MHz up to 865MHz. That covers TV channels 21 to 70. Radio microphones are only designed to tune over a part of that entire spectrum and many were using TV channel 69 which occupies between 854 and 862MHz. The channels that are newly available for microphones are in the range 38 to 40, 606MHZ up to 630 MHz. Channel 69 microphones will not work in channel 38.

The good news

The good news is that channel 70, from 862 to 865 MHz will remain available for license free microphones. Many existing microphones will be able to operate in this channel, though typically only about four at a time without interference in any geographical area. Some new models with tighter frequency management are able to run up to six microphones together in this channel. If you need to use more than six microphones at a time in one area you need to use the licensed frequencies and contact JFMG to arrange a license.