NZ Musician

Back in the mid 1980s wireless microphone systems seemed fancy and bloody expensive stage kit, yet soon passed from revolutionary to commonplace in live performance production and short range communications. Not just for music of course; radio mics, transmitters and in-ear monitors have come to play a pivotal, if purposely invisible role in all manner of theatrical performance, public speaking, media recording and broadcast, live sport presentation, gym classes, bingo halls, churches – and any number of other aspects of our daily lives.

Nady VHF units were first promoted in NZ Musician’s pages in 1989, but the VHF band models proved relatively inflexible and these days most wireless units operate on the much tighter wave UHF band, in a frequency spectrum they share around the world with TV broadcasting.

Under NZ law all forms of radio transmitters must be licensed, with most radio microphone and in-ear monitor systems automatically covered by a General User License (GUL). So long as the product meets the relevant technical specifications, and is operated within the broad conditions of the GUL, users don’t need an individual license in their own name. The license document in question stems from the Radio Communications Act 1989, and is issued by Radio Spectrum Management (RSM), a division of the Ministry of Economic Development (MED).

The GUL document basically permits users to operate wireless units in the upper part of the UHF band between 646MHz - 806MHz, as long as they avoid using the same frequency as an active television service operating in the same area. Operational problems have generally arisen only when someone nearby (within 100-200m) happens to be using a wireless on the same UHF frequency – easily enough overcome with the commonly used multi-frequency switchable wireless systems.

In May 2007, the government-backed Freeview began its new digital television (DTV) service, transmitting at first only via the satellite, which unfortunately doesn’t allow the bandwidth necessary for transmission in that latest couch-bound consumer must have – ‘high definition’.

Since April this year Freeview has been providing the same selection of digital channels using traditional terrestrial transmission sites throughout the country. This service, called Freeview DTT, is a high-definition (HD) version of the DTV service which can be received using existing household UHF aerials (plus a set-top digital receiver). The trouble is DTT broadcasts use big chunks of the same UHF spectrum which has been increasingly used by the comparatively low power wireless devices for a couple of decades now.

Radio mic systems used indoors, especially with line-of-sight between transmitter and receiver may remain unaffected by DTT interference, but performance issues now typically encountered include increased signal dropouts, decreased operating range and unwanted noise. Wireless users reported problems as soon as trial Freeview DTT transmissions began, but of course those problems subsequently disappeared again once testing was completed. In November 2007, when test transmissions took place in Wellington, Te Papa was one big wireless user to take a hit – about $25,000 worth of the museum’s in-house equipment was suddenly rendered useless. The MED subsequently supplied a spectrum-planning chart but at the time the wireless industry had precious little idea about what was coming.

The balloon soon went up big time and professional suppliers of wireless microphone technology scrambled to respond to their customers’ sudden frustration and natural anxiety. Not all brands were affected (since each work over different parts of the UHF spectrum), but a united front was going to be needed from industry members. Haresh Bhana of Elephant Audio is a freelance TV sound engineer with plenty of OB (outside broadcasting) experience. He tells the story of being in Hamilton to prepare wireless equipment for a Black Caps’ one day cricket game against England in March this year. Fortunately cricket broadcasts have a set up day (unlike rugby for instance), because Bhana’s spectrum analyser revealed that all his usual kit was unusable. Hamilton’s Freeview transmission bandwidth was (unknown then to him) now in test mode and he had to quickly sub hire alternative equipment from Auckland.

In February this year David Fuller of Jands NZ and Stephen Buckland from Sound Techniques made a presentation on the developing issues to the Wellington Audio Association. A meeting of interested parties at an Auckland city pub in April led to the formation of a committee which includes representatives of suppliers, hire companies, live sound, OB and film. A strategic plan was developed for the committee to lobby government on several issues. The Wireless Users of NZ (WUNZ) group have met twice since and are engaged in ongoing discussions with representatives of the MED’s Radio Spectrum Policy and Planning Department. Key issues include ensuring that the wireless user industry is consulted on future UHF spectrum developments so it won’t be caught out again. WUNZ is also seeking allocation of dedicated spectrum and the ability to operate radio mic units at higher power.

The MED was initially "arrogant and ignorant" according to one observer, ignorant of the critical need for available wireless spectrum and apparently arrogant enough to not have even discussed the matter with senior TVNZ sound engineers, let alone wider industry users. Subsequent discussions have fortunately proven convivial, the MED’s radio spectrum policy reps gaining understanding as the bigger picture has been painted by WUNZ. New Zealand (the government and MED especially included) increasingly wants to attract international events like V8 racing, the rugby World Cup and TV productions like The Amazing Race, on which production crews expect to be able to use the same equipment that works for them in other countries. Of course most OB equipment is frequency agile, typically across a range up to 26MHz – until recently a comfortable operating window. But if that equipment range coincides with three adjacent 8MHz digital TV bands it would leave just 2MHz bandwidth remaining available for the multi-use needs of such a big event. Travelling stage spectaculars may be hampered, and even lucrative international motion picture filming could potentially be jeopardised, if uncompromised radio communications cannot be guaranteed.

Trouble was the MED really had no idea of the scale of the use of radio microphone systems, much less the potential economic impact that messing with the status quo might cause. Under the GUL licensing scheme, wireless is a distant secondary user group to television, the primary user of UHF spectrum, and as such required (and so received) no consultation. All the planning had revolved around TV usage – none at all around the current or future needs of wireless spectrum users.

Hamilton provides a prime illustration of spectrum log jam with six new digital channels all allocated adjacent places across the UHF spectrum, blocking out a 48MHz-wide hunk of bandwidth. (See the chart below. Note that each allocation of 8MHz bandwidth can support four or five DTT channels.) Any wireless products factory-set to operate in that range are potentially rendered useless in the ’Tron. That’s a worst case scenario and there are plenty of hardware options, but the inevitable result for all wireless operators and users in NZ will be increased investment, complexity and costs. One reason for developing the Freeview platform was to speed the introduction of digital transmission, and come 2015 it is planned that the last analogue TV broadcast will give way to our spectacular digital-only future. 2010 is a stepping stone year towards finalising analogue shut off (ASO).

Post ASO the likely option being considered at government level is for TV channels to then be reshuffled towards one end of the allocated UHF spectrum, leaving the other end free for wireless or other use/exploitation. That sounds sensible enough, but (added costs apart) WUNZ members have grave concerns about the possible real outcome. When a substantial block (700-800MHz) of UHF spectrum was offered for sale by US officials (FCC) in February this year, guess who bought it up? Google and friends sprung US$19B, largely with an eye to its possibilities for the next generation of frequency-roving WiFi products (referred to as White Space devices). Now, no one can imagine our own government turning their back on that sort of potential income from the sale of a few measly airwaves.

While wireless microphone users can currently continue to use all presently ‘unoccupied’ UHF TV spectrum from 646MHz-806Mhz, DTT uses up a substantial chunk of the UHF TV spectrum (see the chart below) meaning that some television channels previously vacant may in short order be filled. TV licences again come up for renewal in 2010 and some analogue TV channels will likely then be moved sideways in some regions (Auckland for instance, where only one HD block is currently shown on the chart), to accommodate the new digital licences. A so-called fourth Digital License (DD) was put aside for the use of establish free-to-air channel Prime, but Prime has been strategically kept out of the Freeview stable by owners Sky Network. If that decision is reversed even more UHF spectrum will be turned over to digital TV usage.

There are 20 or so wireless mic and in-ear monitor brands licensed and available in NZ, with some unlicensed ones also being used. David Fuller says new wireless buyers do need to beware, but adds there is no need to panic. The MED is responding positively and with due care conflict remains avoidable for "legacy wireless" users. If you intend taking your performance on the road then buying a cheaper fixed-frequency device is clearly a false economy, but (more costly) frequency-agile units will continue to work in most situations.