My SBR Ondolina 1926.

SBR radio, Ondolina model. Year : 1926

Aluminium front plate (alas! spoiled); and wood cabinet covered with black «Perkaline».

This radio was sold under the «PANRADIO» logo... I search every information about this logo and distribution. It is write: «pour l'usage exclusif des particuliers en Belgique seulement» (for exclusive use of the particulars in Belgium). Was it for a question of export license?? This logo est write on the cabinet.

This model was build by the SBR between 1924 and 1928. there was 6500 pieces sold during this 4 years of production. Several looks have been designed. Front-plate in cooper, aluminium, ... Varnis or covered cabinet. the electronic has several versions, too. the first models didn't have the varible resistors (heating) and the volume selector.

The look is unusual for this era. It has a totally different look than it was usually done in 1924. There is a harmony in the presentation, with the tubes over the knobs, and the front plate paint with silk-screen. It's fun to see: for the following serial of radios since 1928-29, there was no paintings on the front plates...

It was probably a high-end model for the era. And who can, in the 20's, buy a radio?

Two photographs of the interior (clic to enlarge...). The frame is build with massive copper. Coils are fitted into aluminium tubes.

The supply was done with batteries: 4V for heating and 120V plate voltage. Wires come out at the rear of the cabinet. Negative bias (grids) is done with a 4.5V battery placed into the radio.

This is a hand-made schematic. (31ko GIF file) 4 tubes; A410: RF preamp, A410: detection, A409: first LF, B409: end LF.

This radio works with regenrative system. First tube increase the RF signal. The second is the detector. The ouptut signal from its plate is feed-back to the precedent stage with the reactor variable capacitor. This will increase the RF amplification. If the operator increase the reaction too much, the system become oscillator. The first tube avoid to have this signal at the antenna. This way to do was obligatory in Belgium. Reaction systems build directly in the antenna circuit were phohibited since 1924.

The two last tubes are an LF amp. The ouptut signal can be take after two (headphone) or four tubes (loudspaeker). The output connectors are «telephone» jacks. If connection of headphone in the «2-tube» jack, the LF stage is powered off by an additional jack-switch. When using output LF stage, the volume can be selected with a 3 position switch. «doux-moyen-fort», meaning: slow-middle-hard.

Two variable resistors are used to adjust the heating voltage of the RF and LF tubes.

Copyright Radiocollection.be - Th.Magis