Yep there are HD-3s and HD-4s. Not sure how many HD-4s there are however.
I don't have an HD Radio, but I know of 2 stations here in Connecticut that have an HD-3 that they use to simulcast an AM.
WDRC-FM: Hartford (Buckley)
102.9 HD1 - Classic Hits of the 60s/70s/80s
102.9 HD2 - 50/60s Oldies
102.9 HD3 - The Talk of Connecticut (WDRC AM 1360)
WKCI-FM New Haven (CC)
101.3 HD1 CHR
101.3 HD2 Dance Music (Club Phusion?)
101.3 HD3 - News/Talk (WELI AM 960)
WX4ESPN Bristol (Experimentally Licensed Station)
98.1 HD1 ESPN Radio
98.1 HD2 ESPN Deportes
98.3 HD3 Alternates between the 4 (formerly 5) ESPN O&O stations.
I don't have an HD Radio, but I know of 2 stations here in Connecticut that have an HD-3 that they use to simulcast an AM.
WDRC-FM: Hartford (Buckley)
102.9 HD1 - Classic Hits of the 60s/70s/80s
102.9 HD2 - 50/60s Oldies
102.9 HD3 - The Talk of Connecticut (WDRC AM 1360)
WKCI-FM New Haven (CC)
101.3 HD1 CHR
101.3 HD2 Dance Music (Club Phusion?)
101.3 HD3 - News/Talk (WELI AM 960)
WX4ESPN Bristol (Experimentally Licensed Station)
98.1 HD1 ESPN Radio
98.1 HD2 ESPN Deportes
98.3 HD3 Alternates between the 4 (formerly 5) ESPN O&O stations.