SBE General Legal Counsel Chris Imlay wrote an excellent article in the June 2017 edition of Signal, the print newsletter of the Society, in which he discusses what spectrum we should expect for wireless microphones after TV stations have moved and mobile carriers like T-mobile have set-up their services. It’s not as bad you might think, but you may have to buy new mics or intercoms.
First, during the transition period between now and the end of Post-Auction Phase Two, April 12, 2019, (San Diego’s date for moving off channels 38 through 51), wireless mic users “can continue to operate normally in the entire 614 – 698 MHz band. However, it will be necessary during this entire period to protect any broadband systems that begin operations during the transition time.”
I’ll try to communicate with T-mobile representatives to get updates about what new broadband operations appear in this band.
That said, you can operate indoors with licensed wireless equipment on TV channels that have signals below -84 dBm. So you could hang a discone, see that signals are low enough to meet this requirement, and operate legally (except for channel 37 (608 – 614 MHz) that is reserved for radio astronomy and some medical telemetry only.
A tip for San Diego users: Channels 14, 15, 16, and 20 are reserved in Southern California for LA and Orange County first-responders–police, fire, ambulance, rescue–and make excellent studio wireless channels. Operating an IFB channel outdoors on these channels is risky, however. There was a case of someone at the Torrey Pines Golf Tournament using a 1-watt wireless IFB system and getting a complaint from a public service radio service in Orange County, and the FCC found the user with DF equipment. I could tell you more stories, but understand that public service users in metro-LA have sensitive equipment and refuse to use directional antennas to discipline their signals.
After April 2019, the TV band between 470 and 608 MHz will continue to be available for wireless microphone and IFB users as close as 4 km outside TV station service contours. What this means is that you can operate your wireless device on TV channels that don’t have San Diego broadcasters occupying them. We don’t know yet whether the FCC will eventually allow San Diego TV broadcasters to occupy channels used in Los Angeles. Right now there are no plans to do so with full-power, full-service operators, but you can bet that will change as low power TV stations work to set-up operations on spectrum they currently have no rights to.
There are a few additional frequencies available. Chris says, “Wireless mics and intercoms can operate in the guard band just above TV channel 37 on an unlicensed basis (2 MHz between 614 and 616 MHz). The power limit for wireless microphones operating in the duplex gap and in the guard band after the transition period is 20 mW effective isotropic radiated power (EIRP). There will be no operation permitted in the 1 MHz segments just below and above the broadband downlink segment (616 – 617 MHz and 652- 653 MHz) after the transition period.
“Keep in mind that the 900 MHz and 1.4 GHz replacement bands available for wireless microphones have attracted the attention of manufacturers. So far, so good.”
There’s a good webinar that covers all of this, given by Shure. You should know it lasts an hour.
There you have it. Watch the SBE36.ORG website and Facebook page for updates. If you have any questions, send me a note. I’m supposed to be up on all of this since I’m continuing my role as NFL Game Day Coordinator in one of the busiest RF markets in the world–Los Angeles.