CV291 mixer diode ("crystal valve")
The foil wrapping is designed to protect it from damage caused by RF fields.
Crystal valves were used in the mixers of radar receivers and were susceptible to burn-out caused by the high RF power of the transmitted pulse. It was for this reason that TR Cells were so vital in single-aerial operation, and also the reason for the development of thermionic diode mixers such as the CV58 and CV258.
(Note: Yes I know it is a semiconductor, but as these crystal valves were so vital to radar and many of my other unusual valves are for radar too, surely this deserves to be an 'honorary valve'!)
This file was last modified
15:04:25, Tuesday September 02, 2014