M
maximumradio
Guest
The hidden channels that are touted in the advertisements for HD-FM were always there in the form of subcarriers. The difference is that the SCA channels were in mono and were/are used for "institutional" /specialized programming such as background music service (Muzak), radio reading services for the sight challenged, paging (Q Page), foreign language programming (was done in Las Vegas years ago) and more. Special receivers costing less than $50.00 each were/are marketed by broadcast equipment retailers and were/are easily available. My point: Nice advertising concept but not hardly the truth.