I have a question about KRUG system:
... what's the use of this weird thing, heating?They are the heart of the SDC system.
They are called "potenciáloszkóp" (potential tube) in Hungarian, I do not know the English word for it.
They are basically analogue vacuum memory tubes storing the transmitted impulse (like a TV screen), than the received pulse is compared to it.
http://www.radartutorial.eu/11.coherent/co07.en.html