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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only.

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Old 17th Sep 2023, 4:56 pm   #1
Ken Taylor
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Default Hole through screening plate

The photo is of a home made 3 valve receiver of the 1930's which is on display at the Bletchley Park Museum. I have recently come into possession of a similar model from a silent key. Both have the RF amplifier valve mounted horizontally through a hole in the screening plate. Having just spent the afternoon on-line searching wireless magazines of the period, I cannot find an explanation for this design, can anyone help?
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Old 17th Sep 2023, 5:52 pm   #2
Leon Crampin
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Default Re: Hole through screening plate

Separation of anode and grid circuits to minimise the possibility of oscillation. Nearly all valves of that era were top cap to anode.

Leon.
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Old 17th Sep 2023, 7:58 pm   #3
G6fylneil
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Default Re: Hole through screening plate

I remember acorn valves were used like that.
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Old 17th Sep 2023, 8:45 pm   #4
Ken Taylor
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Default Re: Hole through screening plate

Thanks, I thought it must have been something like that.

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Old 22nd Sep 2023, 6:23 pm   #5
kestrelmusic
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Default Re: Hole through screening plate

This was done on the Scott-Taggart ST300. It separated the first and second RF stages. Actually quite effective!
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Old 22nd Sep 2023, 8:05 pm   #6
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Default Re: Hole through screening plate

With a non-metallised valve you would see an internal screen, which will line up with the external screen. These screened tetrodes replaced the first generation triode RF amplifiers for much improved gain.
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