The Radio Amateurs Hand Book | Page 3

kept in constant touch with headquarters. Bodies of troops moved alertly and intelligently. Ships at sea talked freely, over hundreds of miles. Scouts reported. Everywhere its invisible aid was invoked.
In time of peace, however, it has proved and will prove the greatest servant of mankind. Wireless messages now go daily from continent to continent, and soon will go around the world with the same facility. Ships in distress at sea can summon aid. Vessels everywhere get the day's news, even to baseball scores. Daily new tasks are being assigned this tireless, wireless messenger.
Messages have been sent and received by moving trains, the Lackawanna and the Rock Island railroads being pioneers in this field. Messages have also been received by automobiles, and one inventor has successfully demonstrated a motor car controlled entirely by wireless. This method of communication is being employed more and more by newspapers. It is also of great service in reporting forest fires.
Colleges are beginning to take up the subject, some of the first being Tufts College, Hunter College, Princeton, Yale, Harvard, and Columbia, which have regularly organized departments for students in wireless.
Instead of the unwieldy and formidable looking apparatus of a short time ago, experimenters are now vying with each other in making small or novel equipment. Portable sets of all sorts are being fashioned, from one which will go into an ordinary suitcase, to one so small it will easily slip into a Brownie camera. One receiver depicted in a newspaper was one inch square! Another was a ring for the finger, with a setting one inch by five-eighths of an inch, and an umbrella as a "ground." Walking sets with receivers fastened to one's belt are also common. Daily new novelties and marvels are announced.
Meanwhile, the radio amateur to whom this book is addressed may have his share in the joys of wireless. To get all of these good things out of the ether one does not need a rod or a gun--only a copper wire made fast at either end and a receiving set of some kind. If you are a sheer beginner, then you must be very careful in buying your apparatus, for since the great wave of popularity has washed wireless into the hearts of the people, numerous companies have sprung up and some of these are selling the veriest kinds of junk.
And how, you may ask, are you going to be able to know the good from the indifferent and bad sets? By buying a make of a firm with an established reputation. I have given a few offhand at the end of this book. Obviously there are many others of merit--so many, indeed, that it would be quite impossible to get them all in such a list, but these will serve as a guide until you can choose intelligently for yourself.
A. F. C.

CONTENTS


CHAPTER
I.
HOW TO BEGIN WIRELESS
Kinds of Wireless Systems--Parts of a Wireless System--The Easiest Way to Start--About Aerial Wire Systems--About the Receiving Apparatus--About Transmitting Stations--Kinds of Transmitters--The Spark Gap Wireless Telegraph Transmitter--The Vacuum Table Telegraph Transmitter--The Wireless Telephone Transmitter.
II. PUTTING UP YOUR AERIAL
Kinds of Aerial Wire Systems--How to Put Up a Cheap Receiving Aerial--A Two-wire Aerial--Connecting in the Ground--How to Put up a Good Aerial--An Inexpensive Good Aerial--The Best Aerial That Can be Made--Assembling the Aerial--Making a Good Ground.
III. SIMPLE TELEGRAPH AND TELEPHONE RECEIVING SETS
Assembled Wireless Receiving Sets--Assembling Your Own Receiving Set--The Crystal Detector--The Tuning Coil--The Loose Coupled Tuning Coil--Fixed and Variable Condensers--About Telephone Receivers-- Connecting Up the Parts--Receiving Set No. 2--Adjusting the No. 1 Set--The Tuning Coil--Adjusting the No. 2 Set.
IV. SIMPLE TELEGRAPH SENDING SETS
A Cheap Transmitting Set (No. 1)--The Spark Coil--The Battery--The Telegraph Key--The Spark Gap--The Tuning Coil--The High-tension Condenser--A Better Transmitting Set (No. 2)--The Alternating Current Transformer--The Wireless Key--The Spark Gap--The High-tension Condenser--The Oscillation Transformer--Connecting Up the Apparatus--For Direct Current--How to Adjust Your Transmitter. Turning With a Hot Wire Ammeter--To Send Out a 200-meter Wave Length--The Use of the Aerial Switch--Aerial Switch for a Complete Sending and Receiving Set--Connecting in the Lightning Switch.
V. ELECTRICITY SIMPLY EXPLAINED
Electricity at Rest and in Motion--The Electric Current and its Circuit--Current and the Ampere--Resistance and the Ohm--What Ohm's Law Is--What the Watt and Kilowatt Are--Electromagnetic Induction--Mutual Induction--High-frequency Currents--Constants of an Oscillation Circuit--What Capacitance Is--What Inductance Is--What Resistance Is--The Effect of Capacitance.
VI. HOW THE TRANSMITTING AND RECEIVING SETS WORK
How Transmitting Set No. 1 Works--The Battery and Spark Coil Circuit--Changing the Primary Spark Coil Current Into Secondary Currents--What Ratio of Transformation Means--The Secondary Spark Coil Circuit--The Closed Oscillation Circuit--How Transmitting Set No. 2 Works-With Alternating Current--With Direct Current--The Rotary Spark Gap--The Quenched Spark Gap--The Oscillation Transformer--How Receiving Set No. 1 Works--How Receiving Set No. 2 Works.
VII. MECHANICAL AND ELECTRICAL TUNING
Damped and Sustained Mechanical Vibrations--Damped and Sustained Oscillations--About Mechanical Tuning--About Electric Tuning.
VIII. A SIMPLE VACUUM TUBE DETECTOR RECEIVING SET
Assembled Vacuum Tube Receiving Set--A Simple Vacuum