Join Date: Jan 2001
Location: South Bend, Indiana
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I think PBS still sends a compliant encoded ATSC (19.3 MB) signal via satellite to digital member stations so they can "pass through" on their DTV channel without decoding/re-encoding.
To prevent mistaken identity they assign a PSIP number higher than that of any other DTV station (i.e., 70 or greater).
The same digital transmitter/channel could be used. These numbers are imbedded in the digital stream along with the audio, video, and other anciliary data.
It's probably that 80.3 is from the PSIP on a PBS nationwide feed and 18.1 is the PSIP inserted during local originations.
My DCT-100 STB allows me to turn off PSIP and then I tune to the DTV channel number. With PSIP enabled, it displays whatever channel numbers are programmed into the digital stream.