BobOnTheJob said:
The mystery to me is that on UHF where interference is much less of an issue, FCC allows HD power to be 20% of analog. But in the case of WHAS 11 where it's really needed, they allow less than 4% of analog--how generous.
Power is measured differently at digital stations, vs. how it's measured at analog stations. Comparing the two is comparing apples & oranges.
In both cases, amplitude modulation is used. The transmitter power is continually changing. We say WHAS-analog is running 135,000 watts effective radiated power, but that's only during the synchronizing pulses - a tiny fraction of the time. The rest of the time WHAS' power is a lot less than 135,000 watts. If they were to sit in black they would be running 100,000 watts most of the time - for any real programming it would be a lot lower - a white screen would take about 17,000 watts. You can predict when the next sync pulse - the next 135,000-watt peak - will happen: it happens 15,734 times a second.
In the case of WHAS-DT, the transmitter power is still continually changing. But you can't tell when; there are no predictably repeating synchronizing pulses. So since you don't know when the next power peak is going to happen, for DTV you measure the power
as averaged over a period of time. WHAS-DT may be quoted as 5,200 watts but much of the time, its power is actually considerably higher.
(that said, that 5,200-watt figure *is* rather low. The station I work for is already on DTV channel 10. We're running about 42,000 watts average power - about nine times that of WHAS' permit - and our antenna is higher. )
Why their power is limited I don't know. Best I can tell the nearest other DTV facilities on channel 11 will be Johnson City, Tenn. and Lafayette, Ind.. There's already an analog station on channel 11 in Johnson City, so it's obviously adequately spaced from Louisville. I'd *think* Lafayette is also adequately spaced for a full-power 11 in Louisville but maybe not?
I do have a vague recollection of WBKI filing to change their C-O-L to Bardstown. Don't see how it could have been approved, as there is no other TV station in Campbellsville, and FCC policy doesn't allow removal of a city's only channel.