High-Frequency (HF) Bands
The high-frequency (HF) bands refer to a range of radio frequency bands allocated for long-distance communication via ionospheric propagation. In the frequency spectrum, HF bands typically cover frequencies from 3 MHz to 30 MHz. HF radio waves can travel long distances by reflecting off the Earth's ionosphere, allowing for global communication without the need for line-of-sight transmission. The HF bands are divided into multiple amateur radio bands, each with specific frequency ranges and allocations for different modes of communication, including voice, Morse code, and various digital modes. Amateur radio operators use HF bands extensively for long-distance contacts, especially for communicating over hundreds or thousands of kilometers. HF bands are also utilized by international broadcasters, maritime and aeronautical communication, and emergency communication networks. Due to their unique propagation characteristics, HF bands are subject to changes in ionospheric conditions, solar activity, and atmospheric noise, which can impact signal propagation and communication reliability. Despite these challenges, HF bands remain vital for global communication and are a cornerstone of amateur radio activity. s://en.wikipedia.org/wiki/High_frequency