By 1940, radars are much, much smaller. I am not sure what is going on but I'll throw in some info.
Example of early gun-laying (guiding anti-aircraft fire) is
Würzburg radar. Those could easily fit on trains or even trucks. The more famous and bigger
Würzburg-Riese could no longer fit on truck but still on railway car. They had 50 and 80 kilometers range respectively, IIRC.
Example of early early warning radar would be American
SCR-270 which required only an generator truck and a trailer for the radar itself. It seems to be able to detect an aircraft at 7,600 meters from 180 km away. Other example would be mentioned German
Freya radar, which also is not really big and had range of 200 km.
The examples Aseaheru provided? The first seems to be British Chain Home. They are big, but that's not because they were good, those radars were actually
fucking shit. I mean, they did their job but they were very crude (they were specifically made to reuse as many commercial parts as possible), very big (much bigger wave-lenght, also resulting in lower accuracy of British radars) and only really suited for British stationary defense (unmovable). Their range was around 190 kilometers, though could be better on a good day.
The second example is German Mammut from 1944-1945. By that time Germans noticed that for the stationary defense a big radar like British have, would be better and the radar itself is actually like six Freyas combined. It never seen much use anyways.
The third example is actually not a Freya radar, it's
Flakleit G,
which is actually not that big, and while I can't find a good image with maybe a soldier for scale,
there are dimensions of the bunker it was mounted on, and while I can be very wrong, it seems the size of the base it's mounted on is 180 cm.