The intention was to equip a version of the Saab B 18B bomber with the radar and give it suitable armament for a night fighter. At the same time the radar equipment was offered to Sweden, the aircraft it was installed in was also offered, at a cheap price.
As they were cheap, faster and had longer range than the projected B 18 version, it seemed like a good deal, and the night fighter B 18 was cancelled. Mosquito was given the designation J 30.
Thus in early 1948 60 Mosquitos were ordered, fitted with sighting radar SCR 720B, navigation radar SCR 729F, radar altimeter APN1 and IFF radar type R3121. Ground radar stations type ERB IIIB were also included.
The first one delivered was painted silver all over, contrary to the contract which specified standard RAF night fighter camouflage of Sea Grey Medium and Dark Green. de Havilland then painted those remaining to be delivered in the correct colours, but with the colours on the top side reversed compared to RAF (is this right, I thought RAF painted their fighters in two versions of the same scheme with the colours reversed?).
They were all assigned to the wing F 1 in Västerås where they were liked for their ability to fly in almost all weathers. Usually they operated in pairs. A Junkers 86 were rebuilt into a flying class room to train operators.
One other problem was that ice build up on the radio antenna often prevented communication. The solution was to extend the UKW antenna inside the fuselage with a simple wire, which worked very well.
Another modification was to reinforce the elevator control links, as there were a few crashes attributed to vibration induced material fatigue in them.
From the beginning it was intended that the Mosquitos should be replaced in service by the night fighter version of Saab 32 Lansen. However, they proved to have a much shorter life than expected, and the last were retired in 1954, after beeing replaced by Venoms.