NAB recently performed a series of tests on 17 wireless FM modulator devices currently on the market today. Consumers use these devices to transmit audio signals from their satellite radio or MP3 player to their in-dash car radio. Tests showed that 13 of the 17 wireless devices (76 percent) exceeded field strength limits set by the FCC.
Six of those devices exceeded the FCC field limit by 2000 percent. One device transmitted a signal that was 20,000 percent stronger than allowed by FCC rules. Many of the devices also transmitted signals that were substantially wider in bandwidth than permitted by the FCC, resulting in potential interference to first and second adjacent channels as well.
NAB has sent letters to both FCC Chairman Martin as well as Senate Commerce Committee Chairman Ted Stevens and Co-Chairman Daniel Inouye notifying them of these results. This study raises many questions about the operation of wireless transmitter devices in broadcast spectrum and should be taken into account when considering any "white space" legislation that would permit unlicensed device operation in TV spectrum.
A full copy of the report can be found at www.nab.org.