The ECF804 is a triode pentode designed for application in wide-band amplifiers and instrumentation. This exhibit is an ECF804R and as yet we have no details on the differences between the R variant and the standard valve.
Wide band amplifiers require a large mutual conductance, and thus initial high gain, to allow feedback to broaden the bandwidth and flatten the pass-band, all at the expense of gain.
The triode is separated from the pentode by a bright electrostatic screen.
This is a true pentode and the suppressor grid can be seen clearly.
The thin glass tube envelope is 20 mm in diameter, and excluding the B9A base pins is 47 mm tall.
