CV56D

CV56 was the first strapped 8-cavity magnetron. It was developed in late 1941 by W.E. Willshaw, A.G. Stainsby and E. Kettenwell of the GEC design team, adding strapping jumpers to a NT98 structure.
Used in the Type 271Q Naval radar, it gave 80 to 100 KW in S-band, at 15KV, 15A peak anode pulses, with an efficiency of about 40%.

CV56 soon originated four frequency selections, identified by suffix A to D. Since the suffixes were printed with different inks and characters in most the available samples, we must assume that they were actually all produced as CV56 and selected on the bench after the sealing-off process. Only later a new sealing process was devised, the straps being slightly bended to adjust the center frequency before the seal-off. CV56A was then re-registerd under the title CV1490