And the weird thing that I haven't seen anyone explain is
how it goes from one to the other, within minutes.



The weakness of the ATSC digital TV system used in the US is multipath.

Multipath simply causes ghosts on analog TV.

But digital TV will crash from too much multipath.


You can have a strong signal strength, but if there is too much multipath it still won't work. Unfortunately, it is hard to diagnose because you cannot see the problem on a TV.

You CAN (sometimes) see the problem on an RF Spectrum analyzer. If are are really into it, you can by a low cost USB dongle RF spectrum analyzer and look at the digital TV signal. You can then see SOME, but not all multipath.

Google key words for the gory details would be "ATSC, Adaptive Equalizer" , multipath, 8VSB vs OFDM, .

M