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Hew to Gonstruct an Efficient Wireless...raphy Apparatus at a Small Cost (1902) wysiwyg://63/http://www.angelfire.com/nc/whitetho/1902cons.htm

the exception of an aerial wire leading upward to a mast 30 or 40 feet high, or the wire may
be suspended outside a building. At the upper end of the wire a copper plate 12 inches square
should be soldered; this is the radiator, and sends out the waves into space; another wire, 8,
leading from the instrument is connected with a second copper plate, 9, buried in the earth.
The wires are then connected to the oscillators--one on either side, as shown in Fig. 2, 6,6.
Thé dérial and éaith wirés may bé Soideréed t6 a bit Of spiral Spring, 45 this forms a Good
connection and one that can be readily removed if necessary. The transmitter may be set on a
table or other stationary place, but for convenience it is well to have the coil and key mounted
on a separate base.

To the receiving device there are more parts than to the transmitter, and ——— — tid
to simply gaze upon the cut, Fig. 3; it would be almost impossible to obtain aes ao. :
a correct idea of the connections. To the layman the most mysterious part 5 ee
of the whole system of wireless telegraphy is the most simple and the www.angelfire.com
easiest understood. I refer to the coherer. Fig. 4 is a diagrammatic view of an experimental
coherer, one that is suitabie for the set in hand, for it is inexpensive, easy of adjustment and
quite sensitive. A coherer, reduced to its simplest parts, consists of two pieces of wire, brass
or German silver, 1-16th inch in diameter, forced into a piece of glass tubing, with some silver
and nickel filings between the ends of the wire at the point, 7.

The brass standards shown, 1, in Fig. 4, together with the set screws and springs, are
merely adjuncts attached to the coherer wires to obtain the proper adjustment and to then
retain it. The filings may be made from a nickel five-cent piece and a silver dime, using a
coarse file. The amount of filings to be used in the coherer can be roughly estimated by having
the bore of the tube 1-16th of an inch in diameter, and after one wire plug has been inserted,
pour ifi enough Of the filirigs to Have a iéngth Of 1-16th inch. Béforé describing thé furiction of
the coherer, it will be well to illustrate the connection of the relay, tapper, sounder and
coherer, and batteries. As shown in Fig. 3 the tapper--the central instrument back of the
coherer--is improvised from an old electric bell, the gong being discarded. The relay, on the
right, should be wound to high resistance, about 100 ohms. It is listed as a "pony relay," and,
like all other parts of the apparatus except the coherer, it may be purchased of any dealer in
electrical supplies. The sounder, on the left, is an ordinary Morse sounder of 4 ohms
resistance. The tapper magnets should be wound to 4 ohms. All should now be mounted on a
base 10 by 16 inches and connected up as the diagram, Fig. 5, illustrates; that is, the terminals
Of thé cohérér aré connected in Seriés With two dry Célis, 2, arid the rélay, 3. Fron the rélay a
second circuit, also in series, leads to the tapper, 6, thence to a battery of three dry cells, 5,
and on to the sounder, 4, and finally back to the relay, 3. This much for the two electric
circuits. The puzzling part to the novice in wireless telegraphy lies in the wires, 7 and 8,
branching from the coherer. These have nothing to do with the local battery circuits, but lead
respectively up a mast equal in height to the one at the transmitting end and down in the
ground, as before described. These are likewise provided with copper plates. As shown in the
engraving, Fig. 3, the connections are all made directly between the relay, coherer, sender,
tapper, and batteries for the very sensible reason that they are connected together with a deal
iéss troubié than by the somewhat neater method of wiring wider the baseboard. This,
however, is a matter of time, taste and skill.

Image = by —_ Now let us see what the functions of each of the appliances constituting

_ the receiver are, their relation to each other, and finally, as a whole, to the
transmitter a mile away. To properly adjust the receiver to the transmitter it
is well to have both in the same room--though not connected--and then test
them out. The relation of the coherer to the relay and battery circuit may be likened to that of
a push-button, the bell and its battery. Coherer and push-button normaily represent the circuit

open. When one pushes the button, the circuit is closed and the bell rings; when the Hertzian

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