alt Hacker NewsHF radio. Highly depdendent on space weather, but generally I can communicate around the world with only 100 watts and a long wire.
Be aware though that transmitting on any radio is like turning on a giant, extremely bright light bulb directly above your antenna. Anyone with basic radio know-how will be able to hear you and locate you.
I had to think for a second to realize that HF means lower frequency than VHF, not high frequency in an absolute sense.