CE Interference Queries Abound in FCC TV ‘White Spaces’ Order
Whether DVD players, VCRs and other “TV interface devices” are more prone than TV sets to interference from unlicensed devices operating on or adjacent to channels 2-4 is among many CE questions for which the FCC seeks answers on use of TV white spaces, according to the Commission order and further rulemaking released last week (CD Oct 19 p1).
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There’s “some support in the record” for barring unlicensed devices from channels 2-4 over interference potential, the order said. Others believe they should be permitted because TV interface devices “are usually connected to a TV with shielded cable that should obviate the interference potential from unlicensed devices on channels 2- 4,” the order said.
The FCC wants to know if cabling between a TV interface device and a TV set “typically provides adequate shielding from unwanted signals on channels 2-4,” the order said: “We also seek information indicating the extent to which such signals may be picked up directly within the TV receiver.”
Several have said TV band transmitters operating near a TV set could cause interference by “direct signal pickup” via the receiver chassis, the Commission said. CEA, MSTV, NAB and others claim such devices will “desensitize” a TV receiver, resulting in interference on all channels. Intel calls direct pickup interference highly improbable, since because newer TVs and set-tops are “nearly invulnerable” to it, the order said. Those operating such units “could reconfigure, relocate or disable their equipment to avoid direct pickup interference,” the Commission quoted Intel as saying.
Concerns that TV band devices could harm TV reception if operated near receivers “are theoretical because no parties have submitted test results showing actual direct pickup interference from TV band devices to TV receivers,” the FCC said. Fixed devices typically won’t be operated as close to TV sets “as some parties assume and should not generally cause interference problems,” it said. A portable device could be located near a TV set, but “such devices are typically under control of the same party who can increase the separation distance between them or cease operating a device to eliminate any interference that occurs,” the order said.
The lab plans several types of test, the order said. The lab now is quantifying DTRV receivers’ interference rejection capabilities, report results by March, the FCC said. Field tests will address low-power devices’ TB-band interference potential in report set for July, the Commission said. DTV converter boxes will be tested when they become available, it said. The Commission will publish final rules on the devices next fall to give makers lead time to design and manufacture new products, it said. By late 2007, the FCC lab will begin accepting applications for certification of these devices, it said. Products won’t be cleared for retail sale until after the Feb. 18, 2009, hard date.
On the hot issue of which power emission rules it should apply to unlicensed devices, the FCC in a 2004 rulemaking proposed requiring that at frequencies above 30 MHz, they be the same as those for PCs, radios and TV sets, the order said. Motorola, NAB, and MSTV believe such limits won’t prevent interference to TV reception because they'll result in field strengths high enough to cause interference to DTV stations’ noise limited contour, the order said. Intel disagrees, and Microsoft believes those limits are “unnecessarily strict,” the Commission said. But those limits “have a long and successful history of controlling interference from a wide variety of devices,” the order said.