Radio Shack

The Vacuum Tube Telegraph Transmitter.–This consists of: (1) a
_source of direct or alternating current_, (2) a _telegraph key_, (3) a
_vacuum tube oscillator_, (4) a _tuning coil_, and (5) a _condenser_.
This kind of a transmitter sets up _sustained_ oscillations instead of
_periodic_ oscillations which are produced by a spark gap set. The
advantages of this kind of a system will be found explained in Chapter
XVI.
The Wireless Telephone Transmitter.–Because a jump-spark sets up
_periodic oscillations_, that is, the oscillations are discontinuous,
it cannot be used for wireless telephony. An electric arc or a vacuum
tube sets up _sustained_ oscillations, that is, oscillations which are
continuous. As it is far easier to keep the oscillations going with a
vacuum tube than it is with an arc the former means has all but
supplanted the latter for wireless telephone transmitters. The
apparatus required and the connections used for wireless telephone
sets will be described in later chapters.
Useful Information.–It would be wise for the reader to turn to the
Appendix, beginning with page 301 of this book, and familiarize
himself with the information there set down in tabular and graphic
form. For example, the first table gives abbreviations of electrical
terms which are in general use in all works dealing with the subject.
You will also find there brief definitions of electric and magnetic
units, which it would be well to commit to memory; or, at least, to
make so thoroughly your own that when any of these terms is mentioned,
you will know instantly what is being talked about.
CHAPTER II
PUTTING UP YOUR AERIAL
As inferred in the first chapter, an aerial for receiving does not
have to be nearly as well made or put up as one for sending. But this
does not mean that you can slipshod the construction and installation
of it, for however simple it is, the job must be done right and in
this case it is as easy to do it right as wrong.
To send wireless telegraph and telephone messages to the greatest
distances and to receive them as distinctly as possible from the
greatest distances you must use for your aerial (1) copper or aluminum
wire, (2) two or more wires, (3) have them the proper length, (4) have
them as high in the air as you can, (5) have them well apart from each
other, and (6) have them well insulated from their supports. If you
live in a flat building or an apartment house you can string your
aerial wires from one edge of the roof to the other and support them
by wooden Paradise Valley Tv District K10ah stays as high above it as may be convenient.
Should you live in a detached house in the city you can usually get
your next-door neighbor to let you fasten one end of the aerial to his
house and this will give you a good stretch and a fairly high aerial.
In the country you can stretch your wires between the house and barn
or the windmill. From this you will see that no matter where you live
you can nearly always find ways and means of putting up an aerial that
will serve your needs without going to the expense of erecting a mast.
Kinds of Aerial Wire Systems.–An amateur wireless aerial can be
anywhere from 25 feet to 100 feet long and if you can get a stretch of
the latter length and a height of from 30 to 75 feet you will have one
with which you can receive a thousand miles or more and send out as
much energy as the government will allow you to send.
The kind of an aerial that gives the best results is one whose wire,
or wires, are _horizontal_, that is, parallel with the earth under it
as shown at A in Fig. 3. If only one end can be fixed to some elevated
support then you can secure the other end to a post in the ground, but
the slope of the aerial should not be more than 30 or 35 degrees from
the horizontal at most as shown at B.
[Illustration: (A) Fig. 3.–Flat top, or Horizontal Aerial.]
[Illustration: (B) Fig. 3.–Inclined Aerial.]