Radio mic challenges past, present…and future (part 1)

From 2013 European legislation stipulates radio microphone operation within 470-790 MHz – but as it turns out, the story is rather more complicated and also involves DVB-T.

One of the important months in recent Italian television history was July 2012 – the month in which the entire TV system switched from analogue to digital terrestrial broadcasting. Now, just consider the extent to which digital wireless microphone technology operates in bands adjacent or very close to those used by DTT to understand the problems that can arise – some of which have already occurred, primarily in areas of high population density.

The pivotal issue stems from the fact that microphones and wireless systems are almost ‘universally available’ for every show or television filming and operate in the same transmission range as digital TV (UHF 470 MHz to 870 MHz).

The propagation of radio signals used by digital radio microphones, so widely deployed in the entertainment world, may easily give rise to serious headaches in some geographical regions where filming takes place in locations too close to the DVB-T transmitting sites.

Companies that manufacture wireless microphones for professional use are not so numerous and each one has attempted to address these problems with contrasting solutions. In addition, some have also proposed finding the free channels on which to operate using a digital-mapping technique that is to be consulted before setting up the shooting location. Such information would be necessary to be able to predict in advance which channels are free for operation. Clearly, this remains science fiction in Italy because the DVB-T situation is not yet conducive to the implementation of a mapping reference.

Many international working groups have also struggled to identify what might be the best practice to operate the microphones in such a landscape. A possible solution resides in the possibility of relying on the use of only very high-end equipment, but this could provide an answer for international broadcasters only.

Even today, common sense would suggest the implementation of a wide-band scanner that can display TV signals in the chosen area alongside wireless microphones that operate within a narrower band, following the carrier and excluding off-frequency signals.

All radio microphones currently operating in a discontinuous manner according to geographical location will nevertheless need reallocation towards lower frequencies where channels are potentially still free, perhaps awaiting a reassignment of DVB-T frequencies.

There can be no doubt that the challenges to radio mic users are considerable: since the end of 2012, the 790 MHz to 854 MHz bandwidth that was previously accessible to radio mics and in-ear monitoring has been assigned to the new telephony services defined by the acronym LTE (Long Term Evolution).