3 ms·
generally defined as 3mhz to 30mhz.
by abruzzi 7y ago
generally defined as 3mhz to 30mhz.
- i_am_proteus 7y agoYes! For those not familiar with radio, HF (high frequency) is a frequency range that's higher than what's used for AM broadcast and lower than FM broadcast. Much lower than frequencies used in WiFi and cell phones. What makes it interesting here is that it's a frequency range that is commonly-used and that also propagates in modes other than line-of-sight. For instance 'groundwave' propagation curves around the Earth because of induced currents in the Earth. This allows HF communication over the horizon. Enthusiasts are regularly able to make contact between continents with amplifier power of less than 5 Watts.
- packet_nerd 7y agoI think groundwave propagation only happens reliably at the extreme low end of the HF spectrum, and is mostly associated with medium and long waves (160m ham band & AM radio for example). For most of the HF spectrum reflections off the ionosphere are the main useful propagation mode. At the short end (like CB radio) bouncing of the ionosphere is harder so line-of-sight is more common.
- sciurus 7y agoYep. https://en.wikipedia.org/wiki/Ground_wave_propagation https://en.wikipedia.org/wiki/Ground_wave_propagation https://en.wikipedia.org/wiki/Skywave https://en.wikipedia.org/wiki/Skywave