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Communications receiver
In a robust hardwood case. Both front and back have a hinged lid with chains. There are grips on the left and right hand side of the case. At the top of the receiver a row of binding posts for antenna, +30 volts, 0, +4 volts, and earth. On the upper side of the ebonite front there are binding posts that make it possible to connect an extra hf pre-amplifier or an lf amplifier. The radio is operated by a number of controls, situated at the front. Sliding resistors for filament and anode voltages are situated at the extreme left and right. In the middle the detector: a Philips C1 gas filled bright emitter. The tube is almost identical to the Philips Ideezet tube, issued in 1918. Behind this tube a four pin connection for a Philips D1 (a later addition?) is visible (see photo below). For tuning two variable condensers are available. Both can be operated by two Bakelite knobs with a scale (0..100). The left one is used to tune the primary (antenna) circuit; the second one is used to tune the secondary circuit. Both circuits form a so called "band-pass filter". This construction offers better selectivity compared to a single circuit. Above the detector a threefold coil base is visible. Coil functions from left to right: primary coil, secondary coil, reaction coil. All coils are plug in types. A set of 11 coils is available. The coils measure 20,5 mm between the pins, a distance that deviates from Dutch standards. A handle with a remarkable long shaft and an extra bearing can be used to change the position the coils on the left and right. The coil on the left adjusts the coupling factor of the band-pass filter, the right coil adjusts the amount of reaction. Band width and selectivity both depend on this. With the coils available the receiver has a receiving range of 250 to 6000 meters. Between the coils and the sliding resistors two further knobs can be seen. The left one is used to switch the antenna circuit (serial/parallel). On the right a bipolar on/off switch that operates the filament voltage and the anode battery. Below the tuning knobs two short-circuit bridges to protect the variable condensers, as well as two sets of terminal sockets for a headset. The fixed condensers are by Dubilier Ltd. All materials, like the terminal sockets, clamps for the detector tube, the coil set, seem to be British (Marconi) and some also appear in the product catalogues of the Dutch NSF factory. The construction of the set suggests professional use. The radio could have been used near a transmitter. Receivers like this were used in shipping and in the army. It could also have been used as an experimental receiver for the Dutch (or Dutch East Indies) PTT.

The circuit of the receiver is almost identical to this circuit, published by J. Corver in 1920.
Data  
   
Dimensions (w×h×d): 47 × 37.5 × 33.5 cm
Made in: ±1920
Purchased in: 2008
Weight: 12.7 kg
 
Valves  
Click on a valve for more information

Circuit

What was broadcast in 1920?
 

Listen to "We gaan naar Zandvoort" sung by Albert Bol with orchestra, recorded in 1920
 
The receiver looks a bit like the long wave receiver shown in the picture opposite (the unit on the left of the table).
The receiver has the same front structure with a centrally mounted valve and two large sliding resistors, left and right on the front. The coils were possibly placed inside this unit.
Dr. Ir. C. J. de Groot ordered the construction of this unit in the Dutch East Indies in the main workshop of the P.T.T Service in Weltevreden. It was shipped to the Netherlands in the second half of the year 1918 with the warship HMS "De Zeven Provinciën". It arrived in February 1919. During the journey, reception tests were carried out.
This unit received the first signals from the 100 kW transmitter Malabar in the Dutch East Indies to the Netherlands on June 5, 1919 at de Meent in Blaricum.
 

The unit arrived in the Netherlands in the receiving station on the Meent in Blaricum. In the picture, left, Mr P.C. Tolk, right, presumably Mr Visser.
 
Detail
Philips 4 volt / 0,5 A low vacuum tube, Va 25-30 volts, presumably a C1, filled with Argon. "8178" is printed on the upper socket, "P" (plate) on the lower socket. The name "Philips" is etched in the glass tube; the glass support structure inside shows the date code 24/3 in ink.
Interior
Visible are two variable condensers with zinc plates. In the middle two Dubilier condensers. On the right a support for the earpiece of a headset.
Top, with a number of binding posts
The closed cabinet
The complete set of inductance coils

Philips receiver tube type C. From a Philips folder, October 1921

This page was last edited on 08.12.2020