High Frequency Phenomena and Experiments
By Federick Von Lichtenow
EXPERIMENTAL electricity in its various phases has always held an
unresistable fascination for me. Under its captivating influence I
find myself experimenting thruout the year, whenever time allows
this, ever in search for the unknown trail leading to some new
wonderland of electrical manifestations. This trail is exceedingly
hard to find, not to speak of the wonderland beyond, in the shape
of a "new discovery"
The principles underlying the thousands of tried experiments are
known to science; and in order to present something perfectly new,
the principle involved must at the same time be a novel one; I have
not succeeded that far, sorry - to say, and the few experiments
given here may be original only in the way in which they are
offered. From a practical or mechanical standpoint they are
worthless; in fact, they would cease to be experiments with the
moment they could be put to a practical use.
EXPERIMEXT No. 1.
A tube of glass about a foot long and one-half inch in diameter is
filled with enough small fragments of carbon (those taken from an
ordinary lead pencil or arc light carbon suffice) so that they
cover its lower surface completely, when placed flat on the table.
The openings at both ends of the tube are plugged up with corks,
thru the centers of which short ends of brass or copper wire are
inserted in order to make connection with the carbon particles. The
outward protruding ends are shaped into rings, preferably soldered
at the joints, (see Fig. 1). The smaller ring connects to one
secondary post of the Tesla coil, while the larger one supports,
and at the same time "grounds." the tube on the table.
As indicated already unipolar current is employed. When the current
passes, wonderfully blue-white sparks run in a steady stream over
the carbon fragments, illuminating the whole tube, while the larger
ring sends off a spray of violet light on its lower curve. Upon
approaching the tube with the hand, fingers spread apart, violet
streamers, accompanied by a sizzling noise, can be drawn thru the
glass into each extended finger, (Fig. 2). The length of these
streaming sparks depends naturally - on the electrical output of
the generating set used.
With only a 1 1/2 inch "Bulldog" spark coil and a standard
"Electro" Tesla transformer of the same make, together with the
proper condenser capacity and a spark gap provided with long,
sharply pointed zinc electrodes, I was able to draw sparks one inch
in length which were visible in a lighted room. However, the beauty
of this experiment can be appreciated to the fullest in perfect
darkness only, when the actual length of the sparks, which are
really considerably longer, may- be ascertained. To heighten the
effect, the spark gap should be darkened also. I may add that the
glass tube soon cracks under the electrical strain and has to be
replaced by a new one.
EXPERIMENT No. 2
A flexible helix wire, having a clip on one end, is connected to
one secondary binding post of the Tesla coil, while the clip
engages in the copper rod attached to the oscillator. This latter
consists of a plate of zinc 8 or 10 inches square and a heavy
copper rod, carrying a 1 inch solid brass ball, brightly polished,
on its end and soldered to it, (see Fig. 3.) Hard-rubber stands as
shown in Fig. 4 support the oscillating plate and afford the proper
In the plane of the waves oscillating from the sheet of zinc, a
large inductance coil, about 2 feet long, 2 inches in diameter, and
wound with a single layer of fine (No. 36 or 38 B. & S.)
insulated magnet w-ire, is then placed. This coil has a binding
post on either end, to which pieces of stout copper wire are
fastened, and may be mounted on a separate table from the one
holding the Tesla set (Fig. 5). Here again the power of the
generating set regulates the distance between the oscillator and
the inductance coil. With the aforementioned, comparatively small
outfit, this distance was limited to a foot and a half on the
Upon the current being turned on and wires approached to within
about 1/4 inch, violet-colored sparks will pass between their
points. If the wire on the further end is now grounded by holding
it in one hand, the sparks will be increased to more than twice
their former length. This experiment affords a very spectacular way
of lighting Geissler and other vacuum tubes. The coil ends should,
for best results, be constructed of some insulating material, or if
made of wood this should be thoroly coated with shellac, the same
as the insulated wire windings.
EXPERIMENT No. 3
An inductance, resembling the secondary coil of an Oudin resonator
is placed within the center of a helix, (see Fig. 6). At the time
when this idea occurred to me, I employed a standard "Electro"
helix, (after having the top removed) and a specially made
inductance coil 8 1/4 inches in height, 2 1/2 inches in diameter
and wound with a single layer of very fine, (No. 36 or 38 B. &
S.) silk covered, magnet wire, thoroly coated with shellac. The
brass ball proper has a diameter of two inches. Both coil ends
consist of solid brass instead of some insulating material for the
sake of other experiments. (Fig. 7)
If the helix is now connected up as shown in diagram, sparks may be
taken off at the coil terminal, Geissler tubes lighted, etc., altho
this coil is in no wise connected to the circuit, both coil and
helix merely working under the principle of the Tesla transformer.
In all these experiments it is imperative to have the connecting
wires as short and straight as possible and also heavy besides.
Both the rubber-covered copper cable and the insulated flexible
stranded copper wire are entirely satisfactory in this respect.
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