L.A. TV Stations Free Up Some Spectrum For Wireless Broadband

alphadogg (971356) writes An effort to free up some of the airwaves used by TV broadcasts and make them available for wireless broadband took a big step forward this week in the U.S. Two TV stations in Los Angeles, KLCS and KCET, have agreed to share a single frequency to deliver their programming freeing up a channel that can be auctioned off to wireless carriers next year. The change, which the Federal Communications Commission calls "repackaging," is possible because digital TV broadcasts don't need the full 6MHz of broadcast spectrum that was used for analog TV.

Comments

Re:Of course they don't need the full spectrum

[Trip Ericson]

Analog power was measured as peak power while digital power is measured as average power. If you measured analog power in RMS, that 100 kW would become about 25 kW (less than the 45 kW ceiling). A similar difference arises between 316 kW becoming about 80 kW (less than the 160 kW ceiling). On UHF, the power difference is 5000 kW for analog versus about 1250 kW for digital, slightly more than the 1000 kW ceiling, but only by about 1 dB.

On top of that, about 50 dB SNR was needed for a clear picture with an analog signal, while a digital signal requires only 16 dB for a perfect decode. So the difference in required SNR is more than 30 dB, but the power change, even if it actually was 5000 kW to 1000 kW, is only 7 dB.

Modern UHF vs. classical UHF

[davidwr]

Modern digital television is on even higher frequencies.[than analog UHF]

Not true. Digital television frequencies are basically the same as the analog ones, with some channels either no longer used or no longer used except under special circumstances (e.g. grandfathered stations, low-power stations, etc.).

In practice, most US digital TV stations are UHF stations between channels 14 and 69.