Meccano Radio

The Meccano Radios

The Meccano radio was first released about Sept 1922 and was advertised in the Meccano magazine of that date. It had a variable capacitor made from 15 P/No 76 plates for tuning and some special insulating parts. The tuning flat coils were wound on slotted insulating material. One coil was the main resonator and the other was the aerial coupling coil that could be adjusted to improve selectivity at the expense of volume. The crystal detector was the open type still available in the 1950’s and used a spring wire “cats whisker” to contact a sensitive point on the galena crystal (lead sulphide). The headphone was a standard telephone earpiece with a reasonably high impedance to reduce loading and make maximum use of the available signal. The set sold for the princely sum of 55/-. A lot of money in 1922. A licence was also required at an additional cost of 10/-

For some reason not explained anywhere it did not meet the approval of the authorities and was withdrawn almost immediately. In October of 1922 a much simpler version was released to get around the problem. This was now called Meccano Radio No1. This set sold also for 55/-. It was far more primitive than the original version. The main coil was now wound on an insulated former about 3” in diameter and tuning was effected by a sliding tap on the main coil. However the crystal detector was now the enclosed type also still available in the 1950’s. Of note was the use of brackets P/No 108 with one side folded over at 90 degrees to hold the sliding contact arrangement. This part was later released as P/No 139 and 139a in 1923.

In May 1923 the original radio was released again as No 2 radio followed by a construction article in June 1923. This version required a special experimenters licence at 15/-. In 1924 a later improved version of Meccano Radio No 1 was released. It now was reconnected with two sliders. One for tuning and one for aerial coupling. The price had now dropped to 29/- for the No1 set and 25/- for a set of parts to build the No 2 set.

The simple open crystal set, as both of these designs were was the way most radio hams and constructors began their hobby right up to the 1970’s. By this time the basic crystal set was taken over by more effective simple radios at a far cheaper price and are now just a novelty item. They still can be made and operated but will no longer be feasible when the change to digital radio is effected.

During world war II. Crystal sets were made by prisoners of war in camps particularly Changi out of a range of odd materials. It was found that quite good detectors could be made with a safety pin and a “Blue Gilette” razor blade.

Construction

For anyone contemplating making a replica. The cylindrical coils need about 70 turns of 18G enameled copper wire on a 3” diameter plastic tube (downpipe). The flat type have about the same number of turns on a 3.5” disk with five or seven radial slots to wind the wire on.

The crystal can be replaced by a solid state germanium diode or you can make an open detector with a piece of springy copper wire sharpened to a point and a galena crystal made from lead and sulphur with suitable holders. I made galena crystals by melting about a cc of lead in a teaspoon over a candle. When the lead was nice and liquid I dropped a similar amount of sulphur into it. There was a blue flash and I was left with a congealed mass of galena that worked great as a crystal. The teaspoon never stirred another cup of tea!

The headphone needs to be the high impedance type and you will need a long aerial wire and good ground.

Meccano Magazine references
Page 6 Sept 1922 First reference to the Meccano radio
Page 6 Nov 1922 First reference to the new Meccano Radio (No1)
Page 1 Dec 1922 Full description of the new version of the Meccano Radio
Page 6 May 1923 Release of Meccano Radio No2
Page 6 June 1923 Construction details for Meccano Radio No 2 (re done 1st ver)
Page 148 Nov 1923 Advertisement for some accessories .1st appearance of Ad
Page 128 May 1924 Small reference to the improved No1 receiver with photo.

Barry

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