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

waves sent out by the distant transmitting coil reach the coherer, the particles of metal filings
cohere--draw closer together--thus closing the circuit, and the relay draws its armature to its
magnets, which closes the second circuit, and then the tapper and sounder become operative.

The purpose of the tapper is to decohere the filings after they are affected by the etheric
waves each time, otherwise no new waves would manifest themselves. The relay is necessary,
since the Maximum and minimum conductivity of the conerer, when Horitial and wheri
subjected to the action of the waves, is not widely divergent, and therefore an appliance far
more sensitive than an ordinary telegraphic sounder is needed; this is provided by a relay,
which, while being much more sensitive, has the added advantage of operating a
delicately-poised lever or armature instead of the heavy one used on the sounder. Signals can
be read from the tapper alone, but to produce dots and dashes--the regular Morse code--a
sounder is essential.

The adjustment of the coherer and its relation to the relay is not as difficult as the final
adjustment of the sounder and tapper, but if the following rules are adhered to carefully, the
result will bé a succéssful receiver.

First arrange the adjusting screws of the relay armature so that it will image hosted by
have a free play of only 1-32d of an inch, when the armature is drawn into rE,
contact with the second circuit connection, just clearing the polar
projections of the magnets; have the tension of the spring so that it will
have only "pull" enough to draw back the armature when there is no current flowing through
the relay coils. Now connect the two dry cells in series with the coherer, Fig. 5. Unscrew one
of the top set-screws, 2, Fig. 4, and then screw up the inner screw, 3, until the current begins
to flow through the circuit and pulls the armature of the relay to the magnets. Tap the coherer
with a pencil while turning the screw of the coherer to prevent premature cohesion, which is
apt to occur by pressure. When absolute balance is secured between the coherer and the
relay, connect in the battery of the second circuit, which includes the tapper and the sounder.
When the relay armature is drawn into contact, closing the second circuit, both the tapper and
the sounder should operate, the former tapping the coherer and the latter sounding the stroke.
The adjustment of the sounder requires the most patience, for it is by the most delicate testing
alone that the proper tension is obtained. This is done by the screw regulating the spring
attached to thé sounder lever.

When ail has been arranged and the local circuit of the transmitter is closed, the spark
passes between the oscillators, waves are sent invisibly through space by the aerial and earth
plates, and radiating in every direction, a minor portion must come into contact with the
receiving aerial and ground plates, where they are carried by conducting wires to the coherer,
and, under the action of the waves, the filings cohere, the relay circuit is closed, drawing the
armature into contact, closing the second circuit when the tapper operates, striking the
coherer tube and de-cohering the filings; at the same time the lever of the sounder is pulled
down, and, by the law of inertia, it will continue to remain down, if a succession of waves are
béing sent by thé transmitter, assiiming thé Kéy is béing held down, producing a dash,
notwithstanding the tapper keeps busily at work decohering in response to the continuously
closing circuit caused by the waves; but the sounder--sluggish in its action--when once drawn
down, will remain so until the last wave is received and the tapper decoheres for the last time,
finally breaking the second circuit for a sufficient length of time to permit the heavy lever to
regain its normal position.

All these various actions require a specific time in which to operate, and so the saemiing
key must be operated very slowly, each dot and dash being given a sufficient length of time
for the passage. of a good ‘spark. With the Marconi, Slaby,. Guarini and all other systems of
Wireless telegraphy | now in Usé, only twelve to fi fleen Words per minute cai Bé séiit. It is atso
well to remember that the higher the wires leading up the mast are, the further the messages

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