Fergus

Eureka

1,000kW is not allowed on VHF. Even on the old analog system, the maximum allowed for highband VHF (chs 7 thru 13) was usually ~316kW. And much less for lowband VHF (chs 2 thru 6).

Maximum power of a station is determined by the frequency the station is using, tower height, antenna type and proximity to other stations that could suffer interference from it.

A rule of thumb for distant digital reception: A station on a taller tower may often be easier to receive than a higher power station on a shorter tower.

HTNut

Doesn't the FCC determine how much a station can output too? I always thought it was on a per station basis but I could be way wrong on that.

Eureka

The FCC allots power levels for all stations individually, based on what I posted above.

Orrymain

I think everyone is right here, that it is a combination of tower and power, not to mention our own receptacles. The other factor is weather. Stations on my DTV come in only in certain conditions of excellence. I've more or less given up on those until I can attend to my antenna.

FOX TV

There are a lot of factors that determine assigned output power (ERP, Effective radiated power). The physical coverage area is the main and starting factor, along with antenna elevation (HAAT), and the gain of the antenna compared to available transmitter power is another big factor, along with feed line loss. All of these factors are figured into the equation.

If you have a lower power transmitter, the gain of the transmit antenna can be increased to allow for lower power transmitters, and this allows full coverage of a market regardless of how much actual transmitter power is available up to a certain limit.

There is also both mechanical and electrical beam tilt that is also figured into the equation in order to keep as much radiation near the ground as possible for the longest distance. Earth curvature creates a "Radio Horizon", which is the point where most of the power is radiated into space due to the curvature of the earth itself.

If you look at cell phone antennas on the cell towers, you will see that the transmit antenna panels are actually tilted down towards the ground, and this is known as Mechanical Beam tilt. This is done to increase the distance of the "Radio Horizon", and keep as much power near the ground for as far a distance as possible before the curvature of the earth allows it to radiate into space. As you can see, it is a complicated process to figure all of this out, with the goal of limiting your coverage area to your assigned DMA (Designated Market Area). Assigned power levels are different for every transmitter site and area.

Currently, most UHF stations are limited to a Megawatt, which is a much higher power level than was analog broadcasting on average. Analog did not run at a set power level for the video. The output power of an analog TV transmitter varied with picture content, but the aural or sound level was fixed at 10% of maximum visual power. The sound power level was fixed because it is FM, which normally transmits at a fixed power level just like FM Broadcasting does. Digital TV transmitters run at a fixed power level at all times, unless the transmitter develops a problem.

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Some people think the Bush administration is responsible for the DTV transition !!