high frequency

Radio astronomy generally uses the terms high frequency and low frequency in a general way, dividing the entire radio spectrum (or sometimes also including medium frequency), often intending the term high frequency to reach or include microwave. I've seen 350 MHz used as a threshold for low frequency (e.g., low frequency radio astronomy) but the threshold probably varies widely based upon the topic of discussion.

In contrast to this, for regulation and communications purposes, the ITU uses the terms high frequency and low frequency for specific communications bands that are far different than the typical language of radio astronomy, though astronomers clearly must refer to these ITU bands on occasion. Some of the ITU bands: