Hole through screening plate - UK Vintage Radio Repair and Restoration Discussion Forum

Ken Taylor · 17th Sep 2023, 4:56 pm

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?

Leon Crampin · 17th Sep 2023, 5:52 pm

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

Leon.

G6fylneil · 17th Sep 2023, 7:58 pm

I remember acorn valves were used like that.

Ken Taylor · 17th Sep 2023, 8:45 pm

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

Ken

kestrelmusic · 22nd Sep 2023, 6:23 pm

This was done on the Scott-Taggart ST300. It separated the first and second RF stages. Actually quite effective!

AC/HL · 22nd Sep 2023, 8:05 pm

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.

17th Sep 2023, 4:56 pm	#1
Ken Taylor Pentode Join Date: Dec 2015 Location: Abingdon on Thames, Oxon, UK. Posts: 116	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? Attached Thumbnails

17th Sep 2023, 5:52 pm	#2
Leon Crampin Octode Join Date: Nov 2005 Location: Surrey, UK. Posts: 1,849	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.

17th Sep 2023, 7:58 pm	#3
G6fylneil Pentode Join Date: Sep 2011 Location: Coventry, West Midlands, UK. Posts: 185	Re: Hole through screening plate I remember acorn valves were used like that.

17th Sep 2023, 8:45 pm	#4
Ken Taylor Pentode Join Date: Dec 2015 Location: Abingdon on Thames, Oxon, UK. Posts: 116	Re: Hole through screening plate Thanks, I thought it must have been something like that. Ken

22nd Sep 2023, 6:23 pm	#5
kestrelmusic Hexode Join Date: Feb 2008 Location: Wrexham, North Wales, UK. Posts: 448	Re: Hole through screening plate This was done on the Scott-Taggart ST300. It separated the first and second RF stages. Actually quite effective!

22nd Sep 2023, 8:05 pm	#6
AC/HL Dekatron Join Date: Nov 2003 Location: Heckmondwike, West Yorkshire, UK. Posts: 9,632	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. __________________ Bill, BVWS member