The electrician 1

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THE ELECTRICIAN, OCTOBER 23, 1914.

THE BALSILLIE SYSTEM OF WIRELESS, TELEGRAPHY
AS EMPLOYED IN THE RADIOTELEGRAPH STA-
TIONS OF THE COMMONWEALTH OF AUSTRALIA.*

BY J. G. BALSILLIE.

" The system of radiotelegraphy employed at the various stations
in the Commonwealth is a unidirectional impulse excitation
system in which the radiator is excited into oscillation by the
use of three circuits permanently associated thereto, which’ three
circuits and the radiator circuits fer the” purpose of definition are

Fic. 1.—Imace oF piscHares IN Rotatine Mirror.
F Speed of mirror, 5,400 revs. per minute. Spark] frequency, 360 per
sec. Wave length, 600 metres. The multiple image is due to,the,thick-
ness of the glass. : way

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termed the priraary, the charging, the exciting and‘radiator circuits.
The primary circuit is connected to the charging cireuit by meansfof
a transformer, and arrangements are made that the electrical period
of oscillation of the charging circuit is in resonance with the forced
period of oscillation of the primary cireuit. The exciting circuit
which forms part of the charging circuit is connected to the radiator
circuit by means of a condenser which is common to both circuits.
The balance of circuits is arranged so that there is noreaction between
these circuits. + In“operation the primary circuit charges the con-
densers, and the gap is so adjusted that the charge has reached its
maxinyun before the condenser discharges across it. The discharge
is not oscillatory, for reasons which are explained later, but a single
discharge. This single discharge reverses the charge on the con-

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Fig. 2.—Diagran or CONNECTIONS OF THE BaLsInLi® SYSTEM.
A=a rotary converter, B=a choking coil for adjusting load, C=the
cimary of a special transformer with high leakage factor, D=the
secondary of this transformer, E= the spark gap, F,G, H= condensers, [=a
spiral choking coil, J=inductance in the exciting circuit, K=inductance
in the aerial circuit.

densers. It is evident that the reversed charge cannot be of the
same value as the original charge, because a certain part of the
energy of the original charge has been absorbed by the radiator, and
on account -of the charging circuit being in resonance with the
primary circuit the reversed charge in the condensers finds a path of

* Paper read before Section G of the British Association at Sydney.

. is referred to the photograph here reproduced (Fig. 1), which is ta

less resistance through the secondary of the transformer than ac
the gap’as the potential of the reversed charge is not sufficien
break down the gap. (By this it is tended that ionisation of
in the gap is not permitted to take place to any appreciable exte
The result is, therefore, that the energy not absorbed from
exciting circuit by the radiator circuit and reversed in polarity
the single discharge of the exciting cireuit finds its way to the
mary circuit via the transformer connecting the primary and ch
ing circuits, wherein it is again utilised. +-..

Briefly, the system is a means whereby a radiator is excited
single impulse produced by the discharge of the condenser each
frequency period, arrangements being provided whereby
portion of the energy not imparted to the radiator is returned to th
source of power, means being provided whereby the return of en
from the radiator to the condenser is prohibited.

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Fic. 3.— Resonance Curve, Norman Raputive Cracuir.

E In this system the tuning of the exciting circuit to the radiat
circuit is resorted to for the purpose of insuring that the condens
discharge circuit shall deliver a portion of its original store of ener;
to the radiator at such a rate that the radiator may most efficienth
absorb it and after this has occurred there shall be no further acti
or reaction between the radiator and the condenser discharg
circuit. : 8
In respect of the single discharge in the exciting circuit the read
by means of a rotary mirror, and which shows a single dischargay
taking place during each period of the low-frequency circuit.

The system will be understood by the following descriptio
Referring to Fig. 2, the frequency of the current taken from

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Curve I. Exciting circuit with spark-coil excitation.
», IL Radiation cirenit with exciting circuit energised as in Cur
rotary converter A is approximately 350 periods per second, B is:
ordinary choke coil with a movable core. The transformer C,
an open magnetic circuit transformer with leakage factor of.
definite value for a reason which will be explained later. The
E js air-cooled with the object of preventing the formation of an arg;
‘Air at the pressure of approximately 100 1b. per square inch
blown through one electrode, and impinges on the other electrod
the diameter of the orifice being about 73 mn. The condensers F
G-consist each of five jars, each having a capacity within 1 per cent. ¢
0-002 rafd. The condenser H consists of 14such jars. Lis the chokin,
coil of such value that it does not offer any appreciable impedane
to the flow of the 350 period current, but offers prohibitive impeda:
to the flow of an oscillatory current as compared with the pati
through H. J is a small tuning inductance; K is also a tuniz