The A22 was the last of the round radio Art Deco designs from the innovative manufacturer, EKCO.
This vintage radio follows the same basic style of the previous round radios, but has a much larger dial, making it easier to locate the required section of the dial for a particular station.
Like the other EKCO round radios, the A22 is also well sought after by vintage radio enthusiasts, and the prices reflect the demand for them as antique radios.
EKCO A22 specifications
The EKCO A22 vintage radio follows a similar pattern to many previous EKCO radios, although significantly updated for post war production and usage.
|Brief Specification for the EKCO A22 Vintage Radio
|Basic description||Superheterodyne broadcast radio in Bakelite Art Deco case.|
|Start of manufacture||November 1945|
|Valves (Tubes)||ECH35, EF39, EBL31, AZ31|
|Type of radio||Superheterodyne (single conversion)|
|Intermediate frequency||465 kc/s|
|Receiver coverage||Long, Medium and Short wave (16 - 50 metres) bands|
|Power||AC: 200 - 250V, 40 - 80 c/s|
|Dimensions||13 inches x 14.6 x 7.5 inches.|
|Colours available||Walnut or Black and chrome|
|Original price||£14 14s plus £3 3s 3d purchase tax.|
A total of four valves were used within the A22 vintage radio - three for use within the actual radio parts of the circuit, and one for the power input rectifier. Interestingly, this is the same number of valves that were used for some of the superhet models of the EKCO round radios.
As this radio was released after the end of the Second World War, the valve types are different to those used in radios released before the war.
| Valve Line-up for EKCO AD36 Radio Receiver Circuit
|Valve Number||Type||Use within the circuit|
|V1||ECH35||Triode hexode acting as RF amplifier / mixer and the triode as an oscillator|
|V2||EF39||Variable mu RF pentode acting as IF amplifier|
|V3||EBL31||Double diode and output pentode|
|V4||AZ31||Power input rectifier|
EKCO A22 circuit explanation
The EKCO A22 vintage radio is a three valve (+ rectifier valve) three band superheterodyne radio. It is designed to operate only from an AC mains supply of between 200 - 250V 40 - 80c/s.
Inside the radio cabinet it can be seen that the radio is based on a circular chassis with a small horizontal compartment.
As with many other EKCO vintage radios as well as those from other manufacturers, the circuit uses a minimum number of valves, but ensures that they all perform a number of functions within the overall circuit.
RF input: The signal enters the radio and is applied to a filter to remove any signals that might appear on the intermediate frequency. This prevents any IF breakthrough that could occur if a strong signal appeared on the intermediate frequency.
In addition to this there is an input tuned transformer to select the required range of frequencies to match the signal frequency to which the whole receiver is tuned. The transformer is tuned with a variable capacitor which is ganged with other sections that alter the received frequency. There are three transformers, one of the each band: long, medium and short wave bands which are switch in or out as required.
First valve, V1: The first valve in the line-up of this antique radio is an ECH35 triode hexode. This acts as an RF stage and mixer as well as the local oscillator.
The triode section of the valve is the local oscillator, tuned with transformers or inductors that are switched in to give resonant feedback between the anode and grid circuits.
The hexode acts as the mixer taking in RF from the antenna front end tuned circuits and has an IF transformer on the output for the output signal at 465 kc/s.
Second valve, V2: The second valve in the A22 vintage radio receiver is an EF39 variable-mu RF pentode which acts as an IF amplifier.
The circuit takes its input from the double tuned IF transformer that is in the anode circuit of the mixer. It then amplifies the signal which is again tuned to the IF using another double tuned IF transformer in its anode circuit.
Third valve, V3: The third valve in the line-up for this antique radio is an EBL31
This valve was designed for use in domestic superhet radio receivers. The use of the EBL31 saved a first audio voltage amplifier triode by driving the output valve directly from the detector. Having two diodes in the envelope, this allowed for the diodes to be used, one as a signal detector and the other as an AGC rectifier.
The output from this valve was passed to an audio transformer for coupling to the internal loudspeaker, or an external one.
Fourth valve, V4: The fourth valve in the line-up acted as a full wave power rectifier.
Unlike previous versions of the EKCO round radios, this vintage radio used a mains transformer which gave additional safety. It also allowed external loudspeakers and the like to be used without fear of an electric shock.
As the last of the EKCO round radios, the A22 antique radio is a special radio in the series of radios produced by the company. However with the age of Art Deco passing, after the war the demand was less and the company moved on to introduce new models of radio that were more fitting to the time.However as a vintage radio, the EKCO A22 is still very well sought after by enthusiasts, and in terms of performance and design,, it is more in line with post war sets, using the standard range of octal valves as well as a transformer for the mains input to provide the safety needed for modern sets.
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