AC TRF
receiver with accumulator for the filament
of the radio tubes
In Slavonic oak
cabinet with black front, black
decorative edges and a hinged door at
the rear.Four coils can be inserted
at the top of the receiver.The
feedback is set by means of a movable
coil.At the top of
the front are the tuning knobs for
primary and secondary tuning. The
electrodynamic loudspeaker is in the
middle, with on the left a milliamp
meter that shows the anode current of
the power tube.
A switch with the positions
"on", "off" and "load" is located to the right of the
loudspeaker.
In the left side are the
antenna connection and the connections
for an accumulator.
The power cord is on the right. At the rear is a
gramophone connection.
Martinus Hellingman in 1957
Because of
the very high weight (over 47 kg),
carrying
handles are
provided on the sides of the cabinet.The
radio was intended for larger spaces,
such as cafes, restaurants or dance
halls.
The radio has
a built-in battery charger, which can be
used to charge the 4-volt accumulator for
the filament current of the three radio
tubes when the radio is
not in use.The heavy built-in power supply
unit provides the plate and filament voltages
for the rectifier and the power tube. Both
the radio and the electrodynamic
loudspeaker were designed by drs M.
Hellingman, teacher at M.T.S Technical
School
in Dordrecht. An article
(in Dutch) that he wrote about the
loudspeaker in magazine Radio Nieuws of
October 1927 can be read
here.
The radio receives medium
wave and long wave, depending on the
coils used.
The receiver
was
introduced on August 20, 1928, when
the first advertisements appeared and
the radio was demonstrated in the
auditorium at Groenmarkt 50,
Dordrecht.A
month later it was demonstrated in the
coffee room of the Dordrecht flower
exhibition.
Listen to "'s
Wonderful" by Ambrose and his Orchestra, recorded
on November 13, 1928.
Back
Back with door opened
Top view
of the receiver
Visible are two
Philips 4001 resistor couplings, tuning
capacitors by General Radio, Benjamin resilient
tube bases, a German Wego capacitor, two Lissen
adjustable resistors and capacitors and
resistors made by Loewe and Dralowid.
Side view
Advertisement in the Dordrechtsche
Courant of August 20, 1928
Advertisement in newspaper "De
Waterlander", September 15, 1928
Article in the
Dordrechtsche Courant, August 20, 1928
Martinus Hellingman on a picture made
in the beginning of the twenties.
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