What is a radar inhibitor's significance to pilots?
 

Checking NOTAMs for Friday 26th April I saw the following NOTAM near my intended route.
What does it mean? What is the significance for a GA pilot? It must have some significance otherwise why publish it.

EGTT/QSPLT/IV/BO/AE/000/033/5302N00030W005
CRANWELL PRIMARY RADAR WILL HAVE RADAR INHIBITORS IN USE

Never heard of it and I was a radar controller for most of my life.

Peril Sensitive screens … ?

That's a poorly worded NOTAM. IMHO. The Cranwell Watchman PSR routinely has one (or possibly) two of its available channels inhibited in order to reduce the amount of clutter shown on the display. By reducing the "output" from the radar head you also reduce the capability to detect aircraft. The controllers shouldn't have to keep transmitting the phrase "reduced traffic information from all around owing to limited surveillance performance" because all the aviators making use of the Cranwell ATC services will have read said NOTAM.
Project Marshall will put it right, eventually.

Possibly means an 'attenuator' will be installed for a radar calibration.

Nope, not an attenuator in this instance. It's a simple case of switching off one, or some, of the radar channels.