QUOTE: the superior performance of the EF50 enabled it to be used in the radar sets of the time. It enabled the British RAF Spitfires and Hurricanes to scramble and take-off in time to meet the oncoming attacks.

https://www.youtube.com/watch?v=AKMH-BPtrCw

ITo find out more about the EF50 valve back in 2016 I used a bunch of them in a valve based CRO.
They are indeed a handy valve , I made the vertical amplifier work very well.

Have a look at Building a valve CRO from junk parts. Feb 2016 in the 'special projects' section.

Fred.

If anyone wants to experiment with LOTS of them, I have a large qty of their B9A successor, the EF80 aka 6BX6.

Didn't know the 6BX6 was related to the EF50. I might have a EF50 in my collection, not sure.

There's lots of 6BX6's from old B&W TVs scrapped from the dumpyard 50 years ago.

You can use 6BX6 to replace EF89 in European radios and get more gain.

Or, in the unlikely event of a shortage of 6BH5 or 6N8 (diodes not used), can rewire the socket and use 6BX6.

Thought I would see this here!

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Unqualified, unsupervised, and inexplicably alive...

I've yet to understand how gain is calculated in valves, I imagine there's a variance in gain depending on plate voltage.
Also how is a superior tube picked out when modifying valve radios to give superior gain in either front end or IF?

how gain is calculated in valves

Watch this (y'all): https://www.youtube.com/watch?v=cAS-Q99rLI0

Hi GTC and BOE.

re the Utube

YeHaH indeed!

That question I have been grappling with for a long while but when the definition is narrowed down to what happens inside a valve Mr Y'all does not do a bad job. The point of view that he uses is the valve manufacturers curves.
When you broaden the question out to using a valve in a radio then that's why you have textbooks with thousands of pages trying to explain how to take ALL the variables into account.

It's best to go back to fundamentals and consider the broad but practical question are we talking about VOLT gain, or, POWER gain?
Then you have to consider the terms Source and Load.

A radio is a good example of both types of Gain.
A micro (watt/volt) amount of energy from an antenna is amplified by gain to a level of volts/watts capable of pushing a loudspeaker coil around.

If you hook the antenna straight to the speaker you cant hear the music.
But provide a watt size power supply capable of moving the speaker and then modulating that power supply with a device that responds to the antenna signal then you can hear the music.
What happened?

That's when you start wondering what the hell it's all about!
The things that happen are far more complex than just the valve itself.

I see the broad view of the entire radio full of valves and coils and am still learning.
Yep its about being in "the valley of despair" in the Dunning Kruger learning curve.

All you can do is keep plugging on and sooner or later all the bits will join together and the light will come on!

Fred.