Planeplotter [PP ] has the ability to assess the rotation speeds of the radar heads in addition to seeking out their approximate location.
What is interesting is that the rpm we are seeing , estimated to three decimal places , varies quite considerably from site to site.
Most are rated 15 by NATS , however none are exactly that figure , tending to be between 15.2 and 15.8
I wondered if perhaps the rotation is checked and calibrated on a regular basis.
Is the true rate exacly 15 and are the variations artifacts of the PP software or do they really rotate at varying rpm ?