Dear Dick, LF Group,
Not much to do with LF I know, but the very interesting book
"Metres to Microwaves" by E.B. Callick has a lot of info on British
valve development in the WWII period, including many detailed
drawings and tables. Obviously, it is mainly about the VHF -
microwave spectrum.
The EF50 gets a mention; it was used a lot as an IF amp. The RL7
was a development of the EF50 with aligned grids to reduce
partition noise, and was developed for use in VHF radar RX front
ends, where it was used as an improved replacement for the
difficult-to-manufacture "acorn" valves. Later, it was re-designated
the EF54.
The EF50 was, in spite of it's external metal can, one of the first
"all glass" valves, in which the base was an integral part of the
envelope. This meant the electrodes could be mounted directly on
the base pins, which greatly reduced parasitic inductance
compared to valves with a pinch seal for the lead-out wires. It also
had relatively high transconductance. These features greatly
improved high frequency and wide band performance. By the end
of the war, minature B7G all-glass valves of american origin, such
as the 6AK5, were making the much bigger EF50 obsolete.
Cheers, Jim Moritz
73 de M0BMU
|
