u/GraugussConnaisseur

If you have dealt with Klystrons, Magnetrons,...from the old days, you will certainly recognize this as a very early Magnetron. (without the big Magnet) The ones in your Microwave oven are built much cheaper now without the crazy complex vacuum tight metal-glass sealings. Also modern magnetrons directly couple into a hollow waveguide and do not use a lambda/4 stub like this one.

This MG8/200 was used in medical equipment and industrial heating devices. It was ABSOLUTELY forbidden to use it for anything military related.

Most interesting is the little metal plate that says "EXPORT RESTRICTION" (Exportverbot in german) with some countries listed below it. All this was due to Germany's role in WW2 and the importance of the magnetron in radar development. All the devices needed to be traceable and therefore unrestricted export was not allowed.

See: "The device that won the war" - The Device that Won WW2 – The Cavity Magnetron | Curious Droid

These very thick walled tubes are around the size of a cat's head and operated at 368Mhz in Push Pull with several Amps peak cathode current. All around with technology of ~1942! Heater current a whopping 31Amps at 2V

Germans did not develop Radar Modulators in the first years. So tank oscillators had to be grid-keyed instead of anode-keyed. What does this mean? The anode voltage of 8kv is always present and the grid is kept highly negative @ -2kV, preventing any current flow. A little modulator allows sharp pulses to enter the grid making in highly positive for 3µs and allowing the oscillator to start. This repeated 500 times a second (Some trials used higher repetition freq. up to 2kHz). The circuit is shown in the pictures. A single half loop of a very thick silver plated rod forms the coil. The grid is coupled more or less by parasitic capacity and the antenne is coupled by another thick half loop of wire.

This changed drastically when Lorenz developed the Hohentwiel airborne radar which used a hydrogen Thyratron to pulse a few kV to the power tubes. Thereby shifting the complexity from high power tubes to modulator tubes, pulse forming networks and oil filled pulse transformers. Germans also tried Trigatrons, which are basically controlled spark gaps, powering the magnetron in the "Berlin" radar.

Around 220 of these Radar units were built - in typical german fashion sometimes in competition with other manufacturers instead of aligning and buidling them in great numbers.

They were not only used on ships, but also on uboats and even for coastal defense. Antennas were always dipole fields as in the last pic

GEMA, Telefunken, Lorenz and Siemens were the big guys here. Everybody had their "favorites". Telefunken was into gun laying radars (after losing to Lorenz with their "Kurmark") and with the Lichtenstein also airborne search radars, GEMA was more for long range search radars (Freya + Wassermann) whereas Siemens developed ultra long range panorama radars (Jagdschloss)

Sources: Kroge, Trenkle, forum-marinearchiv.de, my own heap of junk