Essential if internet is down.
Or if ISPs start blacklisting dissidents.
Hamstudy.org also has test taking sessions available.
>The military renaissance in high frequency communications>According to Pätzold, so-called Skywave HF, which bounces signals off the ionosphere, enables beyond line-of-sight communications across “thousands of kilometers” without requirements. HF communications is also ideally suited to supporting local network coverage. “This offers advantages over SATCOM in urban areas, but also in mountainous areas or far north latitudes where no line of sight to existing satellites is possible,”https://falkenworld.com/2020/09/22/the-military-renaissance-in-high-frequency-communications/
Given the signal/noise relation with high output jamming, I doubt this will help much.