The REL No. 3D is an early unstrapped cavity magnetron operating at 3 GHz and the serial number is 8080. The design was as a direct result of the Tizard mission of 1940. The original experimental British type was the E1189 and the 3D is equivalent to the CV1255.
The Tizard mission that took magnetron sample 12 to the USA and Canada left the sample with the Canadian National Research Council. The NRC X-rayed the sample and reproduced the eight cavity design. REL made radar units including the GL111C and the magnetron was made by Canadian North Electric and hence the NE on the envelope. Production commenced in early 1941.
The body is 37 mm from side to side (top to bottom in the image). The body would be made of copper with brass cooling rings. The central cylinder would sit between the poles of the powerful magnet required to bend the electron flow into a circular motion. The cylindrical cathode and heater sit at the centre of the cylindrical body and the connecting struts seen entering the glass envelopes on the left are the supports for the heater/cathode assembly. The anode is the metal body. The anode would screw into the output waveguide and be held at ground potential. The cathode would be at several kV negative.
A closer look at the evacuation pinch, glass to metal seals for the external connections and the Housekeeper seal between the glass and the copper body.
The screw thread for securing the magnetron into the waveguide. The output probe is 15mm long beyond the glass to metal seal.
The original corrugated cardboard packaging. Many layers with shaped cut-outs.
The three sections of the package. The marks show where the valve sits in the stack of boards.
The magnetron resting on the bottom set of layers and protected by the central sections.
The complete pack. The original adhesive paper that once secured the cardboard stack is seen on the lower part of the image.
All of the layers in place. Some of the lettering is still visible but in sufficient to give any information.
The wide metal envelope is 76 mm in diameter, and including the pins is 180 mm tall.
References: 3002. Type 3D was first introduced in 1940. See also1940 adverts.
