Deborah D. McAdams /
Wireless Mics Afforded Two Exclusive Channels
Wireless mics are a type of unlicensed device, born to some degree by TV
operations. They currently operate in the TV spectrum, but at power levels and transmitter
proximities that don’t interfere with TV signals. Once relegated to major
performances and events like the Super Bowl, wireless mics are now used in
everything from churches and conventions to Broadway shows.
from Part III: “Nine
Vie to Manage White Space Database”)
Their low power and relatively small area of operation renders them vulnerable
to interference. The proliferation of things like security and catering
intercoms, baby monitors and garage-door openers has so crowded the radio
spectrum that broadcasters have all but abandoned the use of wireless mics at
The biggest change to the 2008 rules in last Thursday’s FCC order is the
reservation of two channels between 14 and 51 for their exclusive use. Those
two channels will accommodate at least 16 wireless mics operating at 220 kHz. Wireless
mics will also still be allowed to share TV channels, or in some cases,
register in the TVDB database.
The registration option applies primarily to big events with more wireless mics
than the two reserved and any shared channels can accommodate. Applicants will
have to certify that they are using the two channels and all other available
channels from 7 to 51 (except 37). Registration requests must be made at least
30 days before the event. At least six to eight wireless mics must be operated
in each channel as a benchmark for database registration.
The FCC declined to reserve more than two channels for wireless mics, as some petitioners
requested, but instead urged manufacturers to develop more efficient
“We observe that wireless microphones generally have operated very
inefficiently, perhaps in part due to the luxury of having access to a wealth
of spectrum. While there may be users that believe they need access to more
spectrum to accommodate more wireless microphones, we find that any such needs
must be accommodated through improvements in spectrum efficiency.... We will
continue to pursue this issue as the commission considers possible repurposing
of the TV spectrum.”
The protection zone for wireless mics was modified in Thursdays order.
Previously, all TVBDs were prohibited from operating within 1 km of registered
wireless mics. Now only the fixed, 4 W TVBDs are restricted at 1 km. The
lower-power 400 mW portable TVBDs will have a 400 meter radius of restriction.
Part V: “Commissioners React to