Originally Posted by New2OTA
what is the ratio of Digital to Analogue power required to provide equal coverage area? I know its not a simple answer but a ballpark figure?
ERP is a calculated value, not a measured one, and it is too complicated a set of formulae for even most ballpark figures of ▒5kW, for instance.
It depends on how granular you need the guess to be. 2kW can make a world of difference between 2 different stations, usually for a variety of other reasons that just broadcast power. Just like with home OTA reception, location (in 3 dimensions) is everything.
About the only time you can make a rough guesstimate is with 2 stations on nearby channels (like 32 and 34, for example) on the same tower at almost the same height with the same transmitter at the same input power, and even then you still haven't taken into account the beam pattern, tilt, and other factors.
A perfect example of different variables is KOMO-DT in Seattle, which just changed the position of their broadcast antenna on their tower, made no other changes, yet have had a correspondingly large boost to their coverage area.