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Using the 954 and 955 Acorn Valves in Shortwave Receivers

Acorn Valve

In the mid 1930's RCA produced the Acorn valves consisting of a 954 Sharp cut-off Pentode and 955 and 956 Triodes.
With an upper working frequency of 400Mhz these valves were mass produced in the USA during the Second World War for a lot of electronic equipment. And a large number were imported into the UK.
They started being released for sale by the military in the early 1950's and although they found some use in the Radio Constructor market they did not attain the prominence of the EF50.
However at least one shortwave kit supplier in the UK used the 954 in a shortwave set, using the valve not as a pentode but as a triode.
The valves are still availiable today at very low prices, the holders are also availiable.For a couple of suppliers see the article on Circuits for Acorn Valves.
The following are articles on the valves from the mid 1950's describing the use and building of a couple of radio receivers.

RCS Acorn Valve ReceiverHere are details of an RSC (a British supplier) radio using an Acorn 954 valve and is complete with circuit and parts list.

Using VHF Acorns Page 1 Using VHF Acorns Page 2
Using VHF Acorns Page 3 Using VHF Acorns Page 4

Short Wave One using the 955 or 954 Acorn Valve

Short Wave One using an Acorn Valve. Page 1
Short Wave One using an Acorn Valve. Page 2
Experimental version of the TRF Shortwave One.
I recently decided to attemp to revive some of the TRF receivers of years ago. This was the first attempt with the Shortwave One whose circuit is outlined above.
Suppliers who can supply the parts today are identified at the end of this article.
The chassis was intended to house two Acorn valves but only one is fitted here.
Shortwave One
Acorn One. Underchassis Acorn One. Valveholder Detail
A 955 valve was used in this version. The shortwave One circuit uses Denco Octal Green Range 3,4 and 5 coils. These are a bit dificult to get now but very shortly a Octal based Coil holder will be availiable to enable anyone to wind replicas of these coil ranges.So watch this space for details of the supplier.
The power supplies I used were 6.3 volts Dc for the heater and a variable 45 to 90 Volt dc supply for the HT. It has worked well at the lower HT voltage and I am attempting to reduce it further. The set was wired exactly as shown in the circuit diagram and it worked first time using old 2000 ohm headphones.Many stations (including South American ones) have been picked up after dark using a wire aerial and a real earth. I then tried replacing the headphones with a resistor and tapping off the AF via a 0.1uf capacitor to enable a transistor amplifier to be used. That worked fine so the next version will use a cheap amplifier IC to drive a small loudspeaker.With another possible version using a DL96 valve as the pentode, again to drive a speaker.
The RF choke and one of the variable capacitors are availiable from component suppliers in the Links section. For the valve and holder visit the Valve and Tube supplies link below.The remaining components you should be able to get from Pete Roberts.
More on this set as I investigate more options.
The chassis has now been modified to make the coil socket usable from the chassis top.
Shortwave One using a 955 valve

Circuits for Acorn Valves

Another article from Practical Wireless in 1961.
This describes uses for the 954 and 955 valves in a detector circuit covering 10 to 2000M, a short wave circuit covering between 2 and 10 metres. Another circuit uses the 955 as a VHF detector. A 954 HF amplifier is described as is the circuit for a Signal Generator and a VHF Wavemeter.
Very much an experimentors valve today but they are still availiable (and the holders) from Valve and Tube Supplies in the UK or Antique Electronics in the United States.

Circuits for Acorn Valves. Page 1 Circuits for Acorn Valves. Page 2 Circuits for Acorn Valves. Page 3

Beginners Short Wave Two

Practical Wireless. Shortwave TwoFrom November 1963 the circuit and build details for the Beginners Short Wave Two was included as a large seperate sheet in the magazine.
Using an Acorn type 954 valve and a 12AT7 this is a compact little set which includes loudspeaker output. Coil winding data is included in the instructions as are the chassis drilling details.
Due to the size of the original sheet it is not possible to have a complete copy of the original sheet on this site so it is shown here as six sheets.
The final two sheets are further instructions about building the set which were as usual printed in the magazine. Thanks to Tim at Isoplethics (sorry no longer trading)for supplying some of these pages.
Before ill health forced him to cease trading Tim supplied a chassis for this radio and it is currently under construction.
Short Wave Two Radio
Short Wave Two Circuit
Short Wave Two Parts List
V1 and Coil Details
V2 and Coil Winding Layout
Short Wave Two. Above Chassis
Short Wave Two. Below Chassis
Short Wave Two. Chassis Driling
Shortwave 2. Page 1
Shortwave Two. Page 2

955 Acorn Valves and valveholders
Some of the Acorn Valveholders in my collection and a couple of 955 Acorn valves

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Last updated 13.1.2008
2003-2008 © Maurice Woodhead