Why radar picket submarines were awkward

Were radar picket submarines actually used, or only proposed?

The idea was explored, but active radar conflicted with a submarine's need to crash-dive; passive electronic-warning roles proved more compatible with submarine strengths.

The answer distinguishes an exposed active radar set from passive listening equipment. A submarine that must protect a delicate radar installation before diving compromises its principal defence. Passive antennas can instead listen for aircraft and radio activity while preserving the boat's ability to disappear quickly. That better fit between platform and mission later encouraged electronic-surveillance capabilities on attack submarines.