Alex Milne is marketing manager at Boston-based RF Venue, a manufacturer of wireless audio antennae and hardware. With the FCC planning to make big spectrum changes, we asked him whether wireless system users have reasons to be concerned.
The reigning atmosphere in the United States is that of uncertainty. As in many other countries, a large percentage of UHF spectrum currently used for OTA TV is being cleared for other purposes – mostly cellular services and mobile broadband.
Since almost all professional wireless audio devices operate on UHF broadcast band frequencies between 470-698MHz, these changes threaten the pro-audio community with significant hardship.
Six years ago, in 2008, the FCC removed wireless audio devices from the 700MHz band when they repacked 700MHz TV stations into lower channels as a byproduct of the DTV transition. In the next six years, the FCC will remove TV stations and wireless mics from the 600MHz band as well.
Unlike the 700MHz band, the federal government cannot evict broadcasters at 600MHz, so they have devised an unprecedented legal manoeuvre called the ‘incentive auctions’ to do so.
The incentive auctions will purchase TV channels from broadcasters and auction them to bidders back-to-back. Some broadcasters may choose to remain on the air, but will be removed from 600MHz and placed on a different channel. In effect, broadcasters can either choose to accept a fat cheque to go out of business, or be compensated for the forced repacking of their stations to a lower channel.
To be blunt: 600MHz will no longer be available for users of wireless audio devices. However, numerous variables make predicting exactly when this will happen difficult.
The auctions may be delayed by litigations, an insufficient number of broadcasters may relinquish their channels, or the repacking of TV stations post auction may take longer than expected.
Of most concern to professional audio is the possibility that spectrum remaining post-auction (~500-600MHz) will be too congested to use. If a large percentage of TV stations choose to remain on the air, the same number of stations will be packed into half the spectrum. Furthermore, the FCC has authorised the operation of a new breed of radio called a white space device (WSD). Presently, WSDs are nonexistent. But if at some point in the future they become ubiquitous, it will be impossible to operate large numbers of wideband FM microphones without interference.
On the bright side, the incentive auctions are not scheduled to begin for another year and a half. Once they are complete, wireless microphones will still have up to 39 months to vacate the 600MHz band. That means, conservatively, the pro-audio community may operate 600MHz equipment for another four to five years.
The FCC has addressed the pro-audio industry directly in two official documents. They have proposed many new bands of operation for our equipment.
There are also a few ways to protect yourself from future harm.
First, avoid purchasing new equipment that operates in the 600MHz band. For projects that require only a handful of channels, strongly consider purchasing equipment in an ISM band like 2.4GHz, 900MHz, or even 5.8GHz.
Second, if you routinely operate 50 or more channels it is essential that you apply for a Part 74 licence as soon as possible. This licence allows greater transmitter power and protection from WSD interference.
Third, arm yourself with the fundamentals of wireless communications. Building reliable wireless systems will require basic knowledge of what radio waves are and how they behave.Frequency co-ordination, external antennas, cavity filters, RFI shielding and other tools will be necessary.
The future of wireless audio in the United States is daunting, but not hopeless.
For more on the impact of planned spectrum changes worldwide, make sure you read Alan March of Sennheiser's take on the UK's current situation.