[RF_Enthusiast]

They’re using the terms “subchannel” and “subcarrier” interchangeably, which is not entirely accurate.

In broadcasting, subchannels refer to the digital subchannels used in digital audio and television broadcasting. In the U.S., subchannels on the FM band are commonly referred to as the “HD-2” or “HD-3” channels. [1]

Conversely, subcarrier channels are not receivable with a consumer-grade radio. [2]

[1] FCC referencing subchannels: https://docs.fcc.gov/public/attachments/DOC-367361A1.pdf [2] FCC Broadcast Radio Subcarriers or Subsidiary Communications Authority: https://www.fcc.gov/media/radio/subcarriers-sca