RF Spectrum April 2017 Update

Friday, April 7, 2017 - 4:18pm

The long-running FCC spectrum auction finally ended bidding last week. It won't officially close for a few weeks, but this milestone does finalize some of the details vital to wireless microphone users:

What's changing about the available frequencies?

470-608 MHz will remain open to wireless microphone users; 609-698 MHz will no longer be available. The 90 MHz loss is obviously not great, but this is a relatively good result - a much larger section of spectrum was on the offering block.

What does the transition period look like?

Starting soon, there's a thirty-nine month period for the change over, so we're looking at the sold frequencies being totally unavailable sometime in early 2020. That said, the new owners will be testing equipment with transmissions in the 609-698 MHz range during the transition period, so you may find increasing amounts of interference in those frequencies.

Things might also be changing in the 470-608 MHz bands since part of the transition involves 'repacking' television stations (i.e. moving channel assignments) within the entire spectrum, so you might find formerly good blocks occupied.

Long story short, extra diligence and preparation when working with any wireless equipment will be warranted.

Kevin Parrish, a longtime RF Engineer for NBC, was kind enough to come by this week and discuss how wireless microphone operators fit into the current and future RF landscape in greater detail:

Can I futureproof my equipment?

There's no cure-all, but, fortunately, there's been a very long wind-up on this process, so manufacturers have been working diligently to provide you with a lot of options. All major wireless systems now offer wideband systems that cover multiple blocks and allow you a lot of options from each single unit. The frequencies covered by a selection of wideband units is shown below.

Wideband-with-Auctioned-Frequencies.jpg

Spectrum analyzers, whether you're using a stand-alone unit or the built-in ones in most wireless systems, will also become a lot more important, since you'll often be competing with a lot of other devices.

In addition to wideband systems, there are also VHF wireless from Radio Active Designs and Lectrosonics, so you can move some of your wireless transmission to lower frequencies; Zaxcom ZHD and Shure ULX-D HD units which can pack signal into a much smaller space; Shure Axient's auto-switching channels to avoid interference; and Zaxcom's transmitters with built-in recorders, when you absolutely need a reliable back-up.

Stay tuned for updates as potential changes regulations open up other wireless bands.

How else can I protect myself?

Become a Part 74 user. The license allows you to reserve channels from white space devices. Most sound mixers may already qualify for the license under the “producers” definition and qualifications have been extended to large sound operations (defined as regularly using at least 50 channels of wireless), opening licensing to rental houses and venues.

It’s not a perfect panacea, but it resolves situations where you know the location in advance, permits higher transmit power, isn’t terribly expensive, and helps show the FCC that this is important to the broadcast community. Local 695 has a good guide here.
Communicate with other frequency users. As Kevin emphasizes above, everyone is in the same boat, so it behooves us to try to work together and online resources have made it much easier to come together whether you're sharing frequency scans on the forums at jwsound or a facebook group or our own Radio Frequency Scan Repository or need to look up the other transmitters in the ares using the database from the FCC, SpectrumBridge, Google, or LS Telecom.

Bottom line, there's still a lot we don't know, but we'll strive to keep you updated. Feel free to ask us questions and we'll do our best.

Good resources for more reading:

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