Expanding on what sciurus said, theres four major issues with Winlink: 1) It uses proprietary PACTOR III and IV modems that only one company makes. This mean

Expanding on what sciurus said, theres four major issues with Winlink: 1) It uses proprietary PACTOR III and IV modems that only one company makes. This means to monitor Winlink you need to shell out thousands of dollars for a modem. 2) PACTOR transmissions don't send any ident in the clear, the ident is part of the PACTOR code. 3) There at least used to be an issue with PACTOR III modems both not detecting transmissions on the same frequency and falsely detecting transmissions on the same frequency, so Winlink stations were told to turn frequency-in-use detection off. 4) Theres a decent number of people who use Winlink as a substitute for Sailmail and thusly are in violation of 97.113(a)5.