This is a radar. Specifically it is the British PLUTO radar from the island of Cyprus. This is its 50 Hz mode of operation, probably equating to a maximum possible detection range of about 3000 km.
It is normal for this radar, and the similar Russian 29B6, to sometimes set on frequency for hours at a time. They both follow propagation to maximize coverage in the desired target area, and if the conditions don't change it can set on a given freq for a long time, on the other hand sometimes it can also move to a new freq in minutes. If you plot the freq vs time you will generally see that they both move down in frequency in the evening (for their locations) and up in frequency in the mornings.
Another video of it here in the same mode of operation:
https://www.youtube.com/watch?v=tU6UTZUCvscThis video is of the radar in its 25 Hz mode, probably equating to a maximum possible range of about 6000 km:
https://www.youtube.com/watch?v=bDgQyvz31M4The PLUTO radar is similar to the Russian 29B6 radar in sound, however they are different. Some users have trouble telling them apart, so I did a short video on the differences between the two signals.
https://www.youtube.com/watch?v=RsmMvOuFtOsT!