Electricity and Life
The Construction of High-Frequency Apparatus for
Medical and Lecture Use
By Frederick Finch Strong, M. D.
Lecturer on Electro-therapeutics, Tufts Medical
In the March number of The Electrical Experimenter the author
pointed out that high-frequency currents, when properly tuned,
acted as "Vital Boosters," increasing all the functions of the body
and helping it to resist and throw off disease. This vitalizing
effect is not due to the mere liberation of heat in the tissues,
for it is produced by the very high-voltage ("Tesla") currents as
well as by the heavy amperage ("D'Arsonval") currents from which
the thermic effects are usually obtained.
When the writer demonstrated the first therapeutic Tesla Coil and
the first Vacuum Electrode - (in 1896 before a Boston Medical
Society) - and suggested that this method was destined to come into
general use as a vitalizing agent, he was laughed at by his
colleagues; yet today there is scarcely a well equipt physician's
office in this country or in Europe that does not contain some form
of therapeutic high-frequency apparatus. Even the barber-shops of
the present time have their small "Violet Ray" outfits: and these
are not by any means "fakes" for they produce real results, such as
the relief of headache, neuralgia, skin diseases, et cetera.
Unlike other forms of electricity, these currents may be
administered to patients with perfect safety. In twenty years'
experience in electro-therapeutics the author has never known of
harmful results from the use of Tesla Currents applied thru a
vacuum electrode. The heavy amperage ("D'Arsonval") currents, owing
to their deep thermic effects, should be used only under the
direction of a physician. The writer is a firm believer in the use
of Tesla currents in the home, if each member of the family could
receive ten-minute daily treatments from a small high-frequency
apparatus, the general standard of health would he greatly
increased. This has been demonstrated in hundreds of cases.
The author has interviewed a number of the more prominent
authorities on medical electricity and they agree as to the
vitalizing effects resulting from daily high frequency treatment.
Anyone who possesses a 1/4 or 1/2 K.W. wireless transformer,
operating on 110 volt, 60 cycle A.C., can easily construct an
efficient high-frequency outfit for medical or lecture use. The
complete equipment includes a .01 microfarad glass plate condenser,
Tesla coil, inductance, spark gap and electrodes.
The Tesla coil is made as follows: (Fig. 3) On a paper mailing tube
2 1/2" diam. and 14" long wind 480 turns of No. 34 D.C.C. copper
magnet wire. Set up the tube in the lathe, apply a coat of orange
shellac, spin on the wire, apply a second coat of shellac and allow
to dry thoroly. The winding occupies twelve inches, leaving a
margin of one inch on each end of the tube.
Leads of light auto (ignition) cable are soldered to the ends of
the winding. A strip of waxed, corrugated paper M, 5" wide is wrapt
around the center of the secondary tube and on this is wound the
primary, consisting of four turns of heavy high tension auto cable,
and thoroly secured by tape; at least a foot of cable should
project from each end of the winding to form the primary leads.
Place the coil in a wax tight box made without nails and embed it
in a mixture of four parts rosin and one part beeswax. It is safer
to boil the coil for an hour in the insulating mixture before
placing it in the box. Coils made in this way by the writer are
still giving good service after fifteen years of use.
The greatest source of trouble in a medical high-frequency outfit
is the spark gap; the one described below is the outcome of many
years experiment. If properly made it will run daily for months
without deterioration. The spark takes place between two pieces of
brass rod 1 1/4" diam. and 3 3/4" long, turned and tapt as shown.
The sparking surfaces are turned in annular grooves with a 60
degree tool. If your lathe has an automatic cross-feed you may set
it to twenty turns to the inch, and turn a spiral groove instead of
the annular rings. After finishing, the brass pieces are heavily
silver plated and mounted in the usual manner as shown. (Fig. 4.)
For currents over 1/4 K.W., a plate of silver should be soldered to
the brass before turning the grooves. This gap will also give
greater efficiency in wireless work as compared with the usual
The connections for the various parts of the apparatus are shown in
Fig. 5. An important feature is the use of an external inductance
or tuning coil "d" in series with the Tesla coil. It consists of 32
turns of No. 8 bare copper wire, wound on a frame 8" diam., with
1/4" between turns. Edgewise wound flat copper strip is better but
(d Fig. 8.) This coil when used in series with the Tesla primary
enables us to tune the oscillating system in perfect resonance when
the capacity of the patient's body is added to the Tesla terminal.
Effects are produced which are impossible with any other method.
The beautiful High-frequency Effluve or brush-discharge, so
valuable in treating pulmonary diseases, and which so few modern
high-frequency machines can produce, is obtainable by the use of
this series inductance. It may also be used, by short-circuiting
the Tesla primary, as an auto-trans former from which may be
derived heavy "D'Arsonval" and "Diathermic" currents as described
in the next article of this series.
For stage demonstration and public lecture work the writer employs
a large high-frequency resonator which produces a tree-like
discharge three feet in diameter (Fig. 1), and gives a heavy arc
over two feet in length. (Fig. 2.) This shows remarkable efficiency
when it is considered that the resonator is excited by a "Type E"
transformer drawing only 1 K.W. and a condenser of but .01 m.f.
capacity. A small rotary spark gap is used such as is supplied by
the E. I. Co. This result is made possible by the use of the
separate inductance in series with the resonator primary (exactly
the same as that described in connection with the therapeutic
apparatus) (d Fig, 8). The writer believes his resonator gives the
most spectacular discharge ever obtained from 1 kilowatt of energy.
Ordinary plate condensers are used, made from 8 X 10 inch negative
glass, coated on both sides with tin- foil 6 x 8 inches (a Fig. 7).
Six pairs of plates assembled into a unit and boiled in wax give a
capacity of .01 m.f. For safety it is better to employ four of
these sections connected in pairs of .02 m.f. each (b Fig. 7). To
run this resonator at full power for long periods of time it would
be safer to use a series multiple condenser consisting of three
sections of .03 m.f. each in series. Such a condenser would contain
108 - 8 x 10 inch plates, and would be expensive, bulky and very
heavy. For this reason the writer has found it much more convenient
to use a single 12 plat (.01 m.f.) condenser across the transformer
secondary and to replace it when it punctures. The large resonator
was operated for six months in lecture and experimental work before
a condenser section broke down.
The cone for the secondary of the large resonator is of heavy
paperboard and was built for the author by Bicknell and Fuller of
Boston. Its dimensions (see Fig. 6) were suggested by Mr. Earle L.
Ovington, the cone being similar in shape to those used by Mr.
Ovington in the New York Electrical show several years ago. Any
amateur can make a cone of this kind by superimposing strips of
heavy paper, soaked in paste, over a wooden framework. The
secondary winding consists of 400 turns of No. 27 D.C.C. copper
magnet wire. Two parallel strands of wire are wound onto the cone,
the adjacent turns in contact; after winding, one strand of wire is
removed, leaving a space equal to the diameter of the wire between
each of the 400 turns. The cone and winding is then treated with
several coats of "Armalac" (ordinary shellac will not answer).
The primary consists of five turns of thin copper ribbon 1 inch
wide, 1/8 inch paperboard strips being placed between the turns.
The diameter of the coil is 24". When completed it is taped and
rotated in a pan of melted wax until thoroly impregnated. The
terminal shown in the photographs is made from a large brass
oilcan, the stem being removed and replaced by a 3" brass
"bed-ball." The terminal is not attached to the cone but simply
rests on its upper surface in contact with the end of the secondary
wire. The primary and secondary are separately supported by square
wooden blocks; the coupling is rather loose, the bottom of the
resonator being at least two inches above the primary. The lower
end of the secondary coil is attached to the inner primary terminal
Perfect resonance is obtained by varying the number of turns in the
inductance coil in series with the primary. (Fig. 8.) This tuning
system enables us to perform many brilliant experiments otherwise
impossible, such as illuminating wires stretched across a lecture
hall, lighting an inverted umbrella, etc. Some new and very
spectacular experiments with this large resonator will be described
and illustrated in an article in next month's "Electrical
Experimenter," entitled "Methods of employing high-frequency
currents in medical and lecture work."
The author is greatly indebted to Mr. O. K. Luscolm, for advice and
assistance which made possible the successful construction of the
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