Why is ATSC on VHF so damn finicky?

[old_tv_nut]

ATSC 3.0 performance is very similar to DVB-2. ATSC 1/2 was chosen mainly due to its superior signal to noise performance compared to DVB with similar data rate. This was a priority to allow the simulcast of ATSC and NTSC in the US environment where common practice was "big stick" broadcasters, each covering a large geographic area. At the time, DVB decoders were still experimental and could not demonstrate the promised ghost canceling capability. (That changed in a couple of years, of course.) By the time the two systems came into actual use, DVB decoders were more capable of handling diffuse ghosts with a smeared range of delays, and rapidly moving (Doppler) ghosts, than ATSC, if the DVB parameters were set by the broadcasters to favor those conditions. However, ATSC still was superior regarding signal to noise ratio. Now that NTSC is shut down, that advantage is less important, although the FCC never raised the ATSC signal levels as they could have after NTSC was gone.

ATSC 3.0, like DVB-2, can take advantage of new broadcast arrangements like single-frequency networks. and likewise has adjustable parameters that can trade data rate for Doppler (mobile) and signal-to-noise (hand-held receiver) performance.