The old steam operated H2S radar as carried on all three V bombers could be modified for limited use as an air to air radar to facilitate the closing stage of an RV. The Victor (and possibly Valiant) had a facility known as Fishpool, where the centre of scan, normally in the middle of the screen, was delayed to give a circle equivalent to the altitude of the aircraft (typically 5 - 6nms) in radius in the centre of the display. Any aircraft within this range could be clearly seen as a response in this circle and then guided to the tanker in conditions of poor vis, or at night. I rarely used it "in anger" as our steely eyed fighter jocks usually picked us up visually before it was needed, but it did come in handy on a few occasions. Available scan was quite good - around 240 degrees, as I recall, but we couldnt look aft.