Interference Issues - TvTechnology

Interference Issues

Two years ago I predicted we would see more interference to analog stations from DTV stations increasing power to meet the July 2005 and 2006 maximization deadlines. Fortunately for analog TV stations, while there may have been some cases of DTV to analog interference, I haven't heard any complaints. Most of the interf
Author:
Publish date:

Two years ago I predicted we would see more interference to analog stations from DTV stations increasing power to meet the July 2005 and 2006 maximization deadlines. Fortunately for analog TV stations, while there may have been some cases of DTV to analog interference, I haven't heard any complaints. Most of the interference complaints concerned other stations interfering with a DTV station. Of course, because DTV interference would look like noise, it may be that viewers experiencing DTV into analog interference simply thought they were receiving a weaker signal.

The threats I reported on last year are still here--unlicensed devices on unused TV channels, Department of Defense (DoD) uplinks on 2 GHz ENG frequencies, Broadband over Power Line (BPL) and allotment of new spectrum for wireless broadband services in the 50 MHz of spectrum immediately below the 3700-4200 MHz satellite downlink band widely used by broadcasters for program distribution. In 2006, I didn't notice any FCC filings complaining about interference from these other services, but that is probably because there are few 3650-3700 MHz links in operations, BPL is limited to a few areas (with most systems using frequencies below the low VHF TV band) and the DoD has yet to move its uplinks to the 2 GHz band from the L-band frequencies recently auctioned for Advanced Wireless Services (AWS). Clarity Media Systems is still attempting to get the FCC to allow it to use the entire 2 GHz broadcast auxiliary service (BAS) band to broadcast programming to truckers at truck stops around the country.

The National Association of Broadcasters and the Association for Maximum Service Television joined the Society of Broadcast Engineers and individual broadcast licensees in fighting Clarity's request for a waiver of Part 78 to allow it to operate a multichannel video programming service on frequencies allotted for the cable TV relay service (CARS) and broadcast auxiliary use. We should know early in 2007 if the FCC will allow this use of CARS and BAS spectrum and if so, what restrictions they place on using the band this way. If Clarity is able to get authorization to use this spectrum, it is likely other companies looking to get into the MPVD business will see this spectrum and possibly other BAS spectrum as a convenient way to avoid participating in an auction for spectrum already allocated for MVPD.

Broadcasters are very concerned about FCC proposals to allow unlicensed devices to operate on unused TV channels. At this year's IEEE Broadcast Technology Symposium, attendees heard that it would be impractical to install enough filtering in devices located in consumers' homes to prevent interference to TV sets tuned to adjacent channels. Congress is pushing the commission to move quickly to open this spectrum for other uses, but so far the FCC has taken a cautious approach. In September 2006, the FCC said, "the record before the Commission does not contain sufficient information to adopt final technical rules for operation of unlicensed devices in the TV bands."

The FCC Office of Engineering and Technology's Proposed Schedule for Proceeding on Unlicensed Operation in the TV Broadcast Bands has several deadlines in 2007. These include a report from the FCC Laboratory on measurements of the interference rejection capabilities of DTV receivers in March; the FCC Laboratory's report on the results of tests evaluating potential interference from unlicensed devices to TV and other radio services in July; and the release of a Second Report and Order specifying final technical requirements for unlicensed devices that operate in the TV bands in October. In December 2007, the FCC schedule calls for the FCC Laboratory to begin accepting applications for certification of unlicensed devices operating in the TV bands and, if certification is granted, manufacturers will be permitted to manufacture and ship products to distribution points. However, the FCC does not plan to allow these units to be sold at retail until after the DTV transition is complete in February 2009.