The Washington herald. [volume] (Washington, D.C.) 1906-1939, 1922-06-18
POWER OF KDKA
Is RAISED FROM
100 TO 500 WATTS
Height of Antenna I'm.
proved and Range
Increased.
DIAGRAMS EXPLAIN
Path of Speakers Voice From
Studio to Receiving Sta
ton Is Shown.
DIAGRAMS EXPLAIN
By ID. G. LITTLE.


improving the height of the an
tenna and raising the power out
put to 500 watts.
Figure / shows in diagrammati-
cal form the path of the speaker:
voice from the studio to the re,
ceiving station. A voice picked vi
by the transmitter in the studio
theater. or church is amplified anC
transmitted by means of a tele'
phone line to the radio station
where II is further amplified and
used to control the output of the
radio transmitter. The radio trans
hitting set is supplied with power
directly from the works power
plant, through a step down trans
former for the vacuum tube fila'
ments and through a special motor
generator set which changes the 22C
volts d. c. to 1000 volts d. c. fol-
the tube plates. The radio trans
mitter changes this power from
1000 volts d. c. to alternating cur
rent power at a frequency of $685.
900 cycles per second 1850 meters
wave lengthy. which Is supplied tC
the radiatinE system consisting OF
antenna and counterpoise. This
tenna system sets up waves in the
eeher which travel outward in al
directions and. intercepting the re-
ceivinC sntennae. set up voltage and
currents which operated the receiv-
ing sets.
In Four sections.
For convenience in studying the
circuits represented by Figure .
which carry wide variety Of fire.
quency. this diagram has been di'
vided into four sections by mean:
of the dotted lines at the right
The lower section. which may bt
considered as the power supply
carries only direct current at 2.00I
volts and low voltage alternating
current at 25 cycles. This IS cycle
current is used only for heating
the ilament. To prevent any Of
the IS cycle voltage being impressed
on the grid flament and plate fla
nlent circuit. the return of the grid
circuits and of the 1000 volts CIR.
cult is connected to the midpoint
Of the resistOr which is shuntec
across the filament. each half oil
the resistor being shunted by .
condenser for by-passing the radio
and audio frequency.
In the next section of Figure 2
in addition to the power circuits de.
scribed. audio frequency voltage 4:
impressed upon the grids of the
incubator tubes varying the poten.
tial of these grids with respect tc
their hlaments according to the
voice waves. by means of the pick
up transmitter and amplifiers.
Four $50 Watt Tubes.
The four $50 watt power tube.
in the upper part Of the set are
the oscillators. which. in commune
tion with the cOndensers and os.
cillatiOn transformer. change the
1000 volt direct-current power into
acknowledgement power at $685..
600 cycles 1850 meters) generatinr
the so-called carrier wave. which
is pressed on the antennae through
a remote controlled double throw
switch, which allows the same an.
tennae to be used for receiving wher
the station is not broadcasting. The
amplitude of the radio frequency
wave thus generated is constant a.
long as the plate voltage on the os
Cillator tubes remain constant, anC
huctuates with the plate voltage
when the latter is varied. Thu.
the upper section Of Figure car.
ries only modulated radio frequenc,
waves. while the third section car,
ries both radio frequency and audic
frequencies. in addition to the 2.OOt
volt direct-current and the IS cy,
Gle acknowledgements power cir
cults.
The function of the FIVE modu.
lating tubes. also rated at 25C
watts each. is to vary the voltage
on the plates of the osciIlator tube:
according to the voice frequency
impressed upon their grids by the
speech amplifiers.
Power Meditation.
This system of meditation I.
known as constant current or DOW.
er meditation and is accomplished
by means of the constant current
choke coil in series with the posi-
tive lead of the modulator and os-
cillator tube plates. The modula.
tor tube grids are held at a static
potential OF so volts negative with
respect to their filaments by mean.
Of a battery. The audio frequency
voltage from the speech amplifier
then adds to or substracts from
this so volts grid potential. At an
instant when the modulator tube
grids have impressed upon them
by the amplifier a small negative
or zero. potential with respect z,
their iaments. the tube impedances
from plate to filament are low and
a large current flows from the
1000 volt direct current circuit 70
the modulator tube plates Be-
cause of the large inductance CSC
henrys) of the audio frequency
choke coils in series with the plate
supply. the total generator cur
rent can change very little in a
brief interval of time. Hence par,
of the generator voltage occurs
across the choke coils. thus lower.
ing the voltage impressed on tn,
oscillstor tube plates and hence the
radio frequency output of the set
output Increased.
The next instant when the modu.
lator tube grids have a high mega.
tive potential with respect to theil
flaments the plate impedance ar,
high and little or no current howi
through the incubator tubes Tn,
choke coils tending always t
keep the total generator curren
constant create a voltage which
adds to the generator voltage anc
this forces most of the current
into the oscillator tubes which in
creases the radio frequency o.
antenna output accordingly. In
this way the audio frequency chok,
coils cause the voltage applied t.
the oscillator tube plates to nuc.
tuate in proportion to the speech
voltage Impressed on the zrids OF