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Digital Dividend for Wireless Microphone Systems

Posted by Rockshop on 3 July 2013

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Senn DD Ready

DIGITAL DIVIDEND

BY JAMES WALDRON

James Waldron is the product manager for Sennheiser Professional products at Syntec in Australia and New Zealand. He talks here about Digital Dividend and why it matters to wireless microphone users.


We all know that Wireless Microphones and In Ear Monitor (IEM) systems use radio waves to transmit the sound wirelessly. You probably also realise that there is a range of frequencies licenced by the New Zealand Government for us to use these systems, so that we don’t cause interference to other users of this wireless spectrum. The range of frequencies licenced in New Zealand for use by wireless microphones and IEM systems is split into a couple of bands: 518 MHz to 582 MHz and 614 MHz to 806 MHz. This spectrum is also licenced for the transmission of Freeview TV across New Zealand. Because analogue TV transmission technology requires that transmitters don’t operate on adjacent channels there has been plenty of space for us to work happily in the gaps between the TV transmitters.

There are significant changes coming for this arrangement and they are coming soon. If you operate wireless audio systems it’s a good idea to learn about what is happening so you can plan what to do when the changes happen.

The use of smartphones and tablets and other mobile devices which use wireless data technology is growing very quickly. All this data uses radio frequencies and as more mobile data is used, more frequencies get used. The growth in mobile data traffic means that new frequencies need to be found to accommodate it. The frequencies used for wireless audio systems and for TV transmission are ideal for this application too.

One of the benefits of Digital TV technology is that TV channel frequencies can be allocated closer to each other than with analogue technology. This means that overall the Digital TV transmitters don’t need as much frequency spectrum as the analogue TV transmitters need.

By switching over to Digital TV transmission, a significant part of the frequency spectrum can be cleared and used for mobile data services. In broad terms, the frequencies above 698 MHz will be cleared of these services and we (and the TV transmitters) will have to operate between 518 MHz at the low end (same as now) and 698 MHz at the top end.

This is not just happening in New Zealand. It has already happened across North America and Europe and is rolling out now across Asia and Australia.

The switchover to Digital TV transmission is well underway across New Zealand and is scheduled to be completed by the end of 2013. The analogue TV stations are being switched off progressively across the country during this year. You can see a map with timing information at this link: http://goingdigital.co.nz/making-the-switch/coverage-areas-2/coverage-areas.html.

The New Zealand Government has announced that it plans to hold an auction in October 2013 so the Telcos can bid for licences to use the frequencies between 698 MHz and 820 MHz. These licences will give their owners the rights to use that spectrum beginning 1 January 2014 and valid until late in 2031. The Government will need to make sure that there no other users operating on those frequencies, so you can expect to see regulations prohibiting operation of these systems beginning January 1, 2014. This means you won’t be permitted to operate a wireless audio system above 694 MHz from January 1, 2014.

This will leave us the spectrum from 518 MHz to 582 MHz and from 614 MHz up to 686 MHz to share with the Digital TV transmitters, just more than half of what was available previously. The other part of the new landscape is that the Digital TV transmitters are operating on different frequencies from their analogue counterparts. We can expect to find that most of the Digital TV transmitters will be operating below 614 MHz. This means it will be crowded between 518 MHz and 614 MHz in many TV markets and difficult to find frequencies available for your wireless audio systems to use. The plans for Digital TV transmitter frequency allocations show that frequencies above 614 MHz will be largely clear of TV transmission, right across New Zealand. It makes real sense to have your wireless audio systems operating on frequencies between 614 MHz and 694 MHz.

What to look for
in new Gear


From January 1, 2014 your wireless audio systems will have to operate between 518 MHz and 582 MHz, and between 614 MHz and 694 MHz. Use on frequencies above 698 MHz will not be permitted, so if your wireless audio systems operate in this part of the frequency spectrum you will need to replace them. You will find the most clear channels to use are between 614 MHz and 694 MHz. With Sennheiser wireless audio systems this translates to the B Band versions in XSW and Evolution G3 Series products, BW Band versions of 2000 Series products and N Band versions for 3000/5000 Series products.

The Summary


The first thing to make sure of is that the new systems operate on the permitted frequencies: 518 MHz to 582 MHz, and 614 MHz to 694 MHz, because these are the permitted frequencies. Your real preference though, should be systems that operate in the upper block, 614 MHz to 694 MHz, because this is where you will find the biggest number of clear frequencies to use across New Zealand.

Remember to look for the switching bandwidth of the product. The larger the switching bandwidth the more frequencies you will have available for you to choose from. The Sennheiser range generally has the widest switching bandwidth of any brand at a similar price point.

A TRUE Dual Diversity receiver will give you more reliable reception than other types of diversity receiver, so that is an important feature to look for, too. Sennheiser uses TRUE Dual Diversity technology in all of its wireless microphone systems, from XSW Series right up to the top of the range 3000/5000 Series.

These are just a couple of the reasons why Sennheiser is the preferred wireless choice of professionals around the world.

You can find more information here: www.ddready.co.nz