A 1 1/2-inch spark induction coil using a condenser and a transmitting helix will send about 10 miles, and a 3-inch coil under the same conditions about 20 miles. A 4 and a 6 inch coil will transmit about 30 and 40 miles respectively.
Fig. 16. Murdock Transmitting and Receiving Set.
The one quarter kilowatt transformer with a helix and four two-quart leyden jars or an equivalent condenser will transmit at least 50 miles with a suitable aerial. Used as a one half kilowatt transformer with a helix and eight two-quart leyden jars, it will send about 100 miles.
Of course, as in the case of the receiving outfits, these distances are approximate and depend upon the location of the station, the nature of the ground over which the messages are transmitted, the kind of receptor used at the receiving station and the efficiency of the operator himself.
Fig. 16 illustrates a complete Murdock transmitting and receiving set. The transmitting outfit consists of a 15-watt induction coil giving about a one-inch spark, a sending helix, oscillation condenser, a key and a double pole double throw switch for changing the antenna and ground from the transmitting to the receiving instruments or vice versa. The spark gap is mounted on top of the coil. The receiving outfit is the same as that illustrated in Fig. 11.
A complete wireless station—outside of the aerial consists primarily of a source of electrical energy, a transformer or induction coil for charging the oscillation condenser, an oscillation condenser, a transmitting helix, a key for breaking the primary current, a spark gap, an aerial switch, a hot wire ammeter for tuning the transmitting circuits, a detector, a receiving tuner, auxiliary tuning apparatus such as fixed and variable condensers, a potentiometer and battery, and a pair of telephone receivers with a headband.
Other apparatus such as switches, insulators, anchor gaps, testing buzzers, reactance coils, grounding switches, etc., have been described in various places throughout the book and their use suggested whenever it is of any advantage.
The choice of transmitting instruments, as with the receiving apparatus, is left entirely with the experimenter so that he may suit his ideas and means. Wherever possible the range and power of the instruments have been given and suggestions made as to the other apparatus which should be used in connection with them so that the completed outfit will bear some sense of proportion.
