Many LPTV licensees seeking to flash-cut from analog to digital operations on the same channel have found that the different co-channel desired-to-undesired (D/U) ratio for digital-into-digital interference versus analog-into-digital interference can pose problems. One New York LPTV has a slightly different problem.
WLNY-TV, which is licensed to Riverhead, N.Y., is experiencing a problem with a proposed flash-cut scenario for its Channel 17 LPTV, WLIG-LP operation, which is licensed to Plainview, N.Y. In this case, the shift to digital will reduce interference, but Section 74.709 of the FCC rules states that a low-power TV station or TV translator station application will not be accepted if it specifies a channel that’s one channel above or below land mobile assignments and its field strength at the land mobile-protected contour exceeds 76 dBµV/m. WLIG-LP is located within the protected Channel 16 land mobile services contour for New York City.
WLNY said WLIG-LP has been operating analog on Channel 17 since 2005 with no interference complaints from users of Channel 16. The station makes the case that transitioning WLIG-LP from analog to digital will actually reduce emissions on Channel 16 and is requesting a waiver of Section 74.709 to allow that. The request states: "…a grant of the WLIG-LP digital Channel 17 proposal will afford the Channel 16 land mobile service significantly more interference protection" than the current analog Channel 17 operation." It further notes that: "…in actuality the flash-cut to digital Channel 17 with a full service mask filter, together with the existing multi-section filter now used by the station, will dramatically decrease out-of-band emissions to the adjacent Channel 16 spectrum and will afford the Channel 16 land mobile service significantly greater protection against interference than currently exists."
The station added: "FCC rules recognize that the out-of-band emissions 3 MHz from the LPTV channel band edge in the land mobile band are reduced 76 dB for digital LPTV operations, compared to 60 dB for analog LPTV operations—a further reduction of 16 dB."
Comments on the WLNY request are due Aug. 15, 2014. Reply comments are due Aug. 29, 2014.
Doug Lung is one of America's foremost authorities on broadcast RF technology. He has been with NBC since 1985 and is currently vice president of broadcast technology for NBC/Telemundo stations.
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