Age of Wireless
Crystal set "Le sans fil" (1925) :
Large tuning coil with two sliders, Oudin system. It is in fact an HF transformer with the primary and secondary on the same winding. This circuit was not very selective. Nevertheless, provided you were near a powerful transmitting station, the reception was loud and clear...with headphones of course ! Galena is a natural lead sulphide, but synthetic galena -more sensitive- was generally preferred for crystal sets.
Ducretet crystal receiver (1923) :
Precision made Oudin system with 2 sets of rotary contacts. French-polished walnut case. Ebonite front panel. Nickeled brass fittings. The crystal detector is a robust military type already in use during World War I . Eugène Ducretet was a pioneer of Wireless in France and all apparatus made his company are very much sought after.
Horace Hurm "Micropost Bureau" crystal set (1925) :
Radios made by Horace Hurm have a very unusual design.They do not have a wood cabinet and the components are modular. A technical concept well ahead of its time.
This crystal set is a Tesla circuit with two mobile ring-like coils and 2 variable capacitors, giving high selectivity.
The "polycontact" detector is a masterpiece in itself. It has 10 selectable cat's whiskers on 10 different spots of the crystal ! Once you have found the most sensitive spot, it is extremely stable.
Péricaud battery radio of 1922 :
This 2 valve radio is one of the first receivers made for the general public . The valves are of the TM type (Télégraphie militaire). According to an advert of the time :
Specially designed for wireless telephony, this set has excellent performance in Paris with an indoor loop aerial and a range of 500 kilometres with an external wire aerial.It operates from batteries : 4 V for filaments and 80 V for the anodes. It can indeed power a horn loudspeaker !
Early radio valves :
All of those valves have a tungsten filament consuming nearly 1 Ampere. The earliest ones with clear glass and copper sockets have been used since 1915.
On top of their high current demand, they did not amplify very much (in fact 10 times only) and they had a short life expectancy. Later, appeared the very decorative blue valves and golden valves. Very attractive for collectors too...
Ducretet receiver known as "Piano" (1923) :
This four valve radio combines a tuning box and an amplifier box in the same cabinet. The result is very elegant and the finish is perfect. All metallic bits are nickeled. Technically, the circuit is T.R.F. (Tuned Radio Frequency) with a regenerative detector giving both sensitivity and selectivity. The amplification from the 4 TM valves allowed loud listening, but musicality was still an unknown concept !
Vitus Neutrodyne Receiver (1925) :
This set is very impressive by its dimensions and the apparent complexity of its controls. Not really "user friendly" but a superb piece of equipment !
Those high-end radios were made for the wealthy amateurs who also had sufficient technical knowledge to operate them... The valves on top are of the "micro-triodes" type, requiring 10 times less current for the filament and amplifying better than the older TM valves ! That was a major breakthrough in the development of radio at home ...
Quick tour continued...
