Portable TVBDs may only operate above 512 MHz in the UHF band. In addition, there are two TV channels in each city that are reserved for use by wireless production audio systems. These are the first 6 MHz TV channels above and below channel 37.
TV channel 37 is the chunk of radio spectrum reserved for the Search for Extraterrestrial Intelligence (SETI) and wireless telemetry, and goes from 608 to 614 MHz.
This is why wireless microphone and intercom systems cannot tune to that range in the U.S. (Try it.)
Submit Requests
The FCC has also authorized TVBD database administrators throughout the country. Their job is to process requests that result in an over-the-air instruction to all TVBDs in a given area to stay clear of a specific radio band that is protected by request.
So if you qualify, you may submit your request for protection from TVBDs. The FCC has specified that this database will be reserved for large special events and broadcasters who are FCC Part 74 licensees.
Most unlicensed wireless operators should prepare to make do with the radio bands that TVBDs are not authorized to operate in. This includes unused spectrum adjacent to TV channels in:
—76-88 MHz low band VHF (TV 5 and 6)
—174-216 MHz high band VHF (TV 7 through 13)
—470-512 MHz TV bands (14 through 20)
—First open TV band above TV 37 in your city
—First open TV Band below TV 37 in your city
Most wireless systems in the U.S. operate in the UHF spectrum, which has created more RF congestion than ever in this band. In addition, all analog wireless systems implement Frequency Modulation (FM), which is spectrally inefficient compared to other forms of analog modulation. Transmitters take up too much spectrum, and each receiver requires over 300 kHz of spectrum to process the information. You can place 10 systems in that amount of space using other types of more efficient modulation.
Be on the lookout for more spectrally efficient products from wireless manufacturers. You should also attempt to escape the UHF band wherever possible. This is especially true since the FCC has stated that you may not seek database protection unless you’ve implemented equipment in other RF bands such as VHF. I anticipate that manufacturers will begin to migrate back to the VHF band in the near future.
So, at least for now, if you maximize use of equipment outside of the UHF band, implement proper RF band planning, and deploy 6 MHz cavity filters on your base station receivers, you’ll likely get through this wave of re-allocations. Watch for future FCC auctions (at www.fcc.gov) that will have a further negative impact on wireless audio equipment.
Stay informed and stay tuned.
James Stoffo is CTO of Radio Active Designs, a new wireless technology company. He also provides wireless and frequency coordination with high-profile performances, events and venues such as the Super Bowl, Broadway theatre, the World Cup, theme parks, NBA All-Star Weekend, the Radio City Rockettes, and many others.