The Electrical experimenter

April, 1918 ELECTRICAL EXPERIMENTER 837
A RADIO BLINKER SET FOR
TEACHING CODE.
The cut herewith shows a new radio
blinker signal set for teaching the code.
This is self-contained in a cabinet, with
sending key and a very sensitive, high
pitched, high frequency buzzer.
The equipment comprises a buzzer and
a lamp which may be operated separately
by means of self-contained battery or outside
current supply, in connection with two-
A New Radio Blinker Set Equipt With Lamp
and Buzzer With Which the Student Should
Learn the Code Quickly.
way switch and sending key. It is one of
the most compact and most efficient devices
available for purposes of practise and
instruction by students in learning audible
or visual signal codes.
It has not only been adopted by the Navy
Department but is used in many branches
of the Government service and by the best
technical and radio schools for instructing
aviators for both army and navy. It
weighs about 1 lb. 6 oz. complete.
A HANDY RADIO CRYSTAL SET.
No more hunting around for that piece
of crystal when the signals are not coming
in strongly, no more soiled and broken
crystals lying around in drawer's corner.
This new radio "De Luxe" crystal set not
only obviates this, but the high class minerals
furnished with the outfit will prove a
boon for every operator.
The outfit consists of a water- and dustproof,
air-tight box of special construction,
as shown in illustration herewith. The box
can be carried easily in the pocket on account
of its flat and neat shape.
It contains: One piece of Radiocite; one
piece of Galena: one piece of Silicon, all
tested.
Besides there is included one 18 Karat
Gold Catwhisker and two phosphor bronze
catwhiskers of different shapes.
The minerals should lie handled only with
pincers, never with bare fingers. The
makers recommend strongly the use of the
At Last A Vest Pocket Radio Mineral Set.
Contains Tested Rediocite, Galena and Silicon
Crystals, Also Gold and Phosphor Bronze
"Cat-Whiskers."
Gold Catwhisker with the Radiocite crystal.
It is especially invaluable on board ships, as
the gold cannot rust and no oxidation can
set in between the catwhisker and the mineral.
CORRECTION!!
Editor of The Elf.ctrical ExpERIM ENTER
Dear Sir:— Will you kindly publish this
statement that the "graphic sign" (aA,
Bbbb, etc.) referred to in leading up to my
remarks on code-learning, in a recent issue
of the Experimenter, as one of the systems
already in use, was invented and copyrighted,
as I am advised, by Mr. F. S. Winger,
of the Winger Electric & Mfg. Co.,
Chicago, III.
Had I known who the inventor of the system
was, I should have been only too glad
to give him credit for it in my article, as I
consider it by far the hest method noiv in
use for representing the characters of the
telegraphic code.
Thomas Reed.
NEW WIRELESS COURSE IS
STARTED AT CORNELL.
A special course in wireless work, designed
to prepare men for service in the
signal corps of the U. S. Army, has been
instituted in the electrical engineering department
at Cornell this term. The course
is being given at the request of the government
in order to fill some of the urgent
needs of this arm of the service. It is offered
to second term seniors only of whom
about 17 have registered to date. Only
students here will be enrolled so far as
present plans go. The government has sent
some special apparatus for the work which
will be in charge of the regular staff of the
department.
= RADIO WRITERS ATTENTION ! ! ! =
Can you write radio articles dealing
= with the practical problems of wireless
= operating? We can use some good
= papers on such subjects as "the tuning
= of radio transmitters"; "the use of the
== wave meter, including its application
= to measuring the frequency, wave
^ length and decrement"; "operation of
EE commercial transmitting and receiving
=B sets"; "the operation of army truck
== sets"; "improyed ways of receiving
= undamped wave signals," also new
= ideas and short-cuts for learning the
= codes. We pay well for all articles
accepted. Help yourself, your maga-
== zine and your country.
illllllllllllllllllllllllllllllllllllllll!lllllllllllllllllllll!ll!!lllllll!lllll!l!ll!ll!lil!lllllllllliy
RADIO COURSE OPENED AT
SYRACUSE UNIVERSITY.
Announcement was made recently that
Syracuse University, Syracuse, N. Y., has
opened its first Government course of instruction
to fit graduates from the College
of Applied Science for radio service in the
Signal Corps.
The teaching of this course of instruction
will be conducted with the greatest of
secrecy. Dean William P. Graham announces.
Every student entering for the
course, is required to take an oath that he
will not reveal any of the instructions given
him.
NEW PHANTOM ANTENNA AND
APERIODIC CIRCUIT.
When radio engineers wish to test out
a radio transmitting set, it is not always
permissible or advisable to connect it up
to a regular aerial. Hence this has resulted
in the development of a localized antenna;
i. e., a form of lumped capacity and inductance
of the correct oscillating proportions,
and so designed as to permit of passing
thru or into it the same amount of energy
in watts as would be sent into the actual
antenna under working conditions. It's the
same as hooking up a water-rheostat to a
dynamo under a load test.
This phantom antenna comprises a mica
condenser of .0004 M.F., capacity connected
:
in series with a resistance of 4 ohms. It
approximately duplicates the average trailing
1^H
wire aeroplane antenna, and has a carrying
capacity of 1.5 amperes, as indicated
by a hot-wire ammeter. It will stand nor-
APERIODIC CIRCUIT 1
type m
.. 1
A New Radio Measuring Instrument. The
"Aperiodic Circuit" Can be Used to Great Advantage
in Determining the Point of Resonance
in Damped Oscillating Systems.
mally a breakdown potential of 7,000 to
8,000 volts, and is very useful for tuning
and testing aeroplane or other radio transmitters
on the ground.
Aperiodic Circuit:
This instrument comprises a small inductance
and large capacity in series with a
crystal detector, with binding posts provided
for connecting a set of head telephones.
It is extremely useful as a tone
tester for observing the quality of tone of
a transmitter, but its greatest utility is
found in its use in determining the point
of resonance in oscillating circuits which
are being excited by a damped wave.
For example : In measuring the natural
period of an antenna the aperiodic circuit
may be coupled loosely to the grounded
antenna, a buzzer-excited wave-meter being
also coupled to the antenna at a point
slightly removed from the aperiodic circuit.
When t he wave-meter is then varied
a loud response will be heard in the aperi-
A "Phantom Antenna" Useful in Testing
Aeroplane Radio Transmitters Without "Flying"
the Apparatus. It Saves Much Time in
Any Such Testing.
odic circuit when the wave-meter is in
resonance with the natural period of the
antenna. This is by far the quickest way to
get the natural period of an antenna.