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Small one-valve battery operated portable receiver

For medium wave reception. Wooden casing, painted black. The sides are covered with black book muslin. This muslin also covers the frame antenna wrapped around the sides. The top and the knobs of the radio are made of bakelite. The radio can be opened by turning the screw in the middle of the front panel. The price was 210 Kč in 1935.

The circuit of the Weekend is based on an invention by E.H. Armstrong from 1922: the super-regenerative receiver. This principle can be used to make a sensitive receiver with a minimal amount of components. A detector with feedback (in this case a A441N, set-up as Negadyne) oscillates in a normal way, but this oscillation is periodically interrupted by a much lower frequency, the quench frequency. This frequency must be just above the audible frequency. As a result, impulse modulation in the anode circuit of the valve is created, in the rhythm of the modulation of the transmitter received.
Advantages are high sensibility and a simple circuit. Disadvantage is the whimsicality of the circuit, specially in low frequencies like medium and long wave.
The extra coil with the 1500 cm capacitor (see circuit) were added to make the circuit oscillate in the quench frequency. (With many thanks to John Hupse)
Serial number: 777
Dimensions (w×h×d): 14,2 × 16,2 × 7 cm
Made in: 1935-1936
Purchased in: 2009
Click on a valve for more information

What was broadcast in 1935?


Listen to "Hola hej!", sung by Kamila Strnadová and Oldřich Kovář, recorded in 1935

On top, two knobs are visible: on the left a rheostat and on the right, tuning. The A441N is mounted in a horizontal position; behind the tube a small mounting board with components can be seen. The thin wire that comes from the variable condenser (top right) and disappears into the wooden panel, leads to a frame antenna inserted between book muslin and the wooden sides and bottom. The battery compartment houses six 4,5 volts batteries (see pictures below).


Vladimír Fiala from the Czech Republic mailed me a scan of the wrapper of a Telegrafia battery
Left: tuning; right, rheostat. Between the knobs a number of  sockets. Top and bottom, across, two connections for headphones. The middle socket can be used for an aerial.
The Telegrafia Weekend, with headphones
The Telegafia Weekend with batteries

This page was last edited on 28.04.2019