What is the main feature of long-range BLOS communications?

The main feature of long-range Beyond Line of Sight (BLOS) communications is that it utilizes specific frequency ranges without the reliance on satellite support. This method allows for effective communication over vast distances using ground-based or aerial relays, which can include high-frequency (HF) bands. In this context, BLOS communications are essential when direct line of sight is obstructed, such as in mountainous terrain or urban settings.

Using specific frequency ranges enables these communications to traverse long distances, leveraging the capabilities of certain frequencies that can propagate further without the need for satellite involvement. This makes it a versatile communication approach suitable for various military operations where establishing a satellite link may not be feasible or practical.

The other options do not capture the essence of long-range BLOS communications correctly. While high-frequency bands can be involved, specifying that BLOS communications concerns only high frequencies does not encompass the full spectrum used. Moreover, the notion that BLOS communications primarily cater to local communication contradicts the primary purpose of long-range capabilities.