DAB has worse behavior with marginal signal quality. When a FM signal may be slightly degraded with static, DAB just gives up entirely.
I really hate that engineers, regulators, and businesspeople managed to work together to make something simple and reliable less reliable but more "modern".
Probably because DAB has been designed to be spectrally efficient, allowing one to cram as many radio channel as possible into a slice of spectrum. It's a property of error control codes, as used in DAB: that the closer one gets to optimal performance, the sharper the cutoff between working and not working. As range increases: works, works, works, BAM, gone...
If it's optimal, the quality of a digital link will be pretty well perfect up until that cutoff (but no link is truly optimal). DAB's design placed emphasis on more channels rather than longer range, so the point at which DAB cuts out will likely be before the point that FM has degraded to unintelligibly. In theory there can be a region where FM has degraded but DAB is still holding up, but in the name of more channels this region is probably small.
> When a FM signal may be slightly degraded with static, DAB just gives up entirely.
You'd think that this would be a good scenario for 'hierarchical modulation':
> Hierarchical modulation is particularly used to mitigate the cliff effect in digital television broadcast, particularly mobile TV, by providing a (lower quality) fallback signal in case of weak signals, allowing graceful degradation instead of complete signal loss. It has been widely proven and included in various standards, such as DVB-T, MediaFLO, UMB (Ultra Mobile Broadband, a new 3.5th generation mobile network standard developed by 3GPP2), and is under study for DVB-H.
I really hate that engineers, regulators, and businesspeople managed to work together to make something simple and reliable less reliable but more "modern".