digital connection

Way back in the last century, amateur radio lost access to the 220-to 222-MHz portion of the 1.25-meter VHF band in the U.S. We haven’t suffered much because of it, but as part of the deal we got secondary access to the 219-to 220-MHz segment, with the Automated Maritime Telecommunications System (AMTS) service being the primary user. But the deal was (and is) that it could only be used for point-to-point digital communications. At the time, the internet wasn’t yet a thing, and packet networks were huge. You can read the history of that 1996 FCC decision, but the “why” is not relevant anymore.

Using 219-220 MHz is not without significant requirements: First, only data emissions are allowed, and the maximum bandwidth is 100 kHz. [97.307(f)(13)] Second, only fixed point-to-point digital links are allowed; “it is not available for other purposes.” [97.303(i)(1)] As a secondary allocation, amateurs must not cause harmful interference to AMTS stations or TV