Fig. 220.—A Diagram showing how to connect some of the Instruments described in this Chapter.
After the instruments are connected, place a piece of galena or silicon in the cup of the detector and bring the wire down on it. Then move the sliders on the tuning coil or loose coupler and adjust the detector until you can hear a message buzzing in the telephones. It may require a little patience and practice, but if you persist you will soon learn how to adjust the apparatus so as to receive the signals loudly and clearly with very little trouble.
The Transmitting Apparatus
Spark coils have already been described in Chapter XII. They may be used to transmit wireless messages simply by connecting to a spark-gap and a key.
Spark coils which are especially made for wireless telegraphy will usually send farther than an ordinary spark coil used for experimental purposes.
Fig. 221.—A Wireless Spark Coil.
A good one-inch coil costs from $4.50 to $5.00 and will send from three to five miles if used with a fair aerial.
A spark coil requires considerable current for its successful operation and will give the best results if operated on storage cells, dry cells, or bichromate cells. If dry cells are used, it is a good plan to connect them in series multiple as shown in Figure 69.
Spark-gaps may be made by mounting two double binding-posts on a wooden base as shown in Figure 222.