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434 Radio News for November, 1928
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Two -Way Regulator Corrects
Line -Voltage Variation
THE small box -shape device illustrated
in this column is a voltage regulator for
use in connection with radio receivers. It
tential to 110 volts for the operation of
the radio receiver, regardless of whether
the line -voltage is above or below this value;
whereas resistors are capable only of reducing
the voltage. Secondly, the unit
has a sufficiently wide range to cover all
conditions; it will increase the voltage to
normal value from as low as 90 volts, or it
will decrease the voltage to normal from
as high as 130 volts. Thirdly, there are
eight voltage taps, thus providing a ver,v
close adjustment. And fourthly, it is highly
efficient, as it regulates the voltage by reactance,
rather than resistance.
The appearance of the device is clearly
shown in the accompanying picture; it is
housed in a metal box 41/4 x 414 x 3'''%
inches and weighs 3 pounds. It is provided
with a cord and plug for connection
to the lamp socket, and also with a 110 -
volt receptacle for the plug of the power
transformer; the only adjustment is a knob
which operates an eight -point switch.
The way in which the unit is connected
is shown in the schematic wiring diagram.
Another illustration shows the mechanical
construction of the combination switch
which automatically connects the voltage -
indicating buzzer when the voltage regulator
is being adjusted. It will be noticed
that the shaft turned by the adjustment
knob is connected to the contact arm of
SW1 and that, as the shaft is turned to
the right, the contact arm of SW1 is turned
and the switch SW2 is closed. However,
as soon as pressure is removed from the
knob, It spring opens switch SW2, thus
disconnecting the buzzer.
Manufacturer: R. B. 3!. Manufacturing
Company, Logansport, Ind.
To obtain 110 -volt current from a variable or
non -standard lighting supply, plug the receiver's
power -unit lead in at B on this device,
and insert C in a light -socket. Adjustment is
made by knob A, as shown in the diagram at
the right.
has been designed to correct the housesupply
voltage to 110, the potential usually
required by electric sets. It will operate
in any A.C. circuit, provided the voltage
is not greater than 130 nor less than 90, and
it has an output of 60 watts, which is ample
for the operation of the average set.
It is not difficult to appreciate the importance
of an A.C. line -voltage regulator,
for the chief cause of dissatisfaction with
electric receivers has been due to the short
life of the tubes. It was first thought by
the experimenters that this condition resulted
from poorly -designed .tubes, but investigation
has shown that variations in
the 110 -volt house -supply current usually
are responsible for overloading the filaments
and reducing tube life. A. majority of the
power transformers available for heating
tube filaments are designed for 110 -volt
operation and an increase in the input voltage
will cause a proportional increase in
the output. Therefore, in cities where the
house potential rises to 120 and 130 volts
during the evening, the tube filaments operated
with A.C. are dangerously overheated.
On the other hand, insufficient power is
frequently the cause of poor reception.
The voltage- regulating device illustrated
on this page provides the broadcast listener
with a very simple method of regulating
the input voltage to a receiver. It is a
simple auto-transformer, equipped with a
special A.C. buzzer which vibrates when
the potential applied to the receiver reaches
110 volts. The interesting feature of the
regulator is that the voltage- indicating buzzer
operates automatically during adjustment,
but is turned off by the removal of
the operator's hand from the adjustment
knob.
Among other advantages it possesses, this
regulator will correct the house -supply po-
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110-V. RECEPTACLE
FOR POWER TRANS-
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T he auto -transformer steps the voltage either
up or down, as required. The correct setting
is indicated automatically by the buzzer; SW2
functions only during the operation of adjustment.
New Short -Wave Plug -In Coils
Small and Rugged
A well -known manufacturer of short -wave
receiving equipment has developed some
new plug -in coils which are small and of
very rugged construction. The coils are
sold in sets of three, as shown in the illustration.
They provide a receiver with a
wavelength range of 15 to 130 meters.
A complete set of these coils consists of
three interchangeable coils, a suitable base
and an adjustable primary, which is
mounted on the base. In each case the
interchangeable coils have two windings, a
secondary and tickler. The coils may be
used in the standard fixed- tickler, capacity -
controlled regenerative circuit, with a 140 -
mmf. variable grid -tuning condenser and a
250 -mmf. variable feed -back condenser.
With this arrangement the smallest coil
provides a wavelength range of 15 to 33.5
meters, the next largest coil has a range
of 31.5 to 68 meters, and the largest coil
has a range of 57 to 133 meters. Also, coils
of the same design are available for higher
and lower wavelengths.
The picture immediately below clearly shows
the skeleton construction of the coils. The
The compactness and convenience of these coils for the short -wave operator may be readily seen.
The secondary- tickler coil at the left is for the 15 -33.5 -meter range, and that at the right for
3L5 -68 meters. The 57. 133 -meter coil is shown plugged into the base; to which the primary is
permanently attached, as it is the some in all combinations.