The Radio Amateurs Hand Book | Page 8

get the owner's, or agent's, permission. This is usually an easy
thing to do where you only intend to receive messages, for one or two
thin wires supported at either end of the building are all that are needed.
If for any reason you cannot put your aerial on the roof then run a wire
along the building outside of your apartment, and, finally, if this is not
feasible, connect your receiver to a wire strung up in your room, or
even to an iron or a brass bed, and you can still get the near-by stations.
An important part of the aerial wire system is the ground, that is, your
receiving set must not only be connected with the aerial wire, but with
a wire that leads to and makes good contact with the moist earth of the
ground. Where a house or a building is piped for gas, water or steam, it
is easy to make a ground connection, for all you have to do is to fasten
the wire to one of the pipes with a clamp. [Footnote: Pipes are often
insulated from the ground, which makes them useless for this purpose.]
Where the house is isolated then a lot of wires or a sheet of copper or of
zinc must be buried in the ground at a sufficient depth to insure their
being kept moist.
About the Receiving Apparatus.--You can either buy the parts of the
receiving apparatus separate and hook them up yourself, or you can buy
the apparatus already assembled in a set which is, in the beginning,
perhaps, the better way.

The simplest receiving set consists of (1) a detector, (2) a tuning coil,
and (3) a telephone receiver and these three pieces of apparatus are, of
course, connected together and are also connected to the aerial and
ground as the diagram in Fig. 1 clearly shows. There are two chief
kinds of detectors used at the present time and these are: (a) the crystal
detector, and (b) the vacuum tube detector. The crystal detector is the
cheapest and simplest, but it is not as sensitive as the vacuum tube
detector and it requires frequent adjustment. A crystal detector can be
used with or without a battery while the vacuum tube detector requires
two small batteries.
[Illustration: Fig. 1.--Simple Receiving Set.]
A tuning coil of the simplest kind consists of a single layer of copper
wire wound on a cylinder with an adjustable, or sliding, contact, but for
sharp tuning you need a loose coupled tuning coil. Where a single coil
tuner is used a fixed condenser should be connected around the
telephone receivers. Where a loose coupled tuner is employed you
should have a variable condenser connected across the closed
oscillation circuit and a fixed condenser across the telephone receivers.
When listening-in to distant stations the energy of the received wireless
waves is often so very feeble that in order to hear distinctly an
amplifier must be used. To amplify the incoming sounds a vacuum tube
made like a detector is used and sometimes as many as half-a-dozen of
these tubes are connected in the receiving circuit, or in cascade, as it is
called, when the sounds are amplified, that is magnified, many
hundreds of times.
The telephone receiver of a receiving set is equally as important as the
detector. A single receiver can be used but a pair of receivers connected
with a head-band gives far better results. Then again the higher the
resistance of the receivers the more sensitive they often are and those
wound to as high a resistance as 3,200 ohms are made for use with the
best sets. To make the incoming signals, conversation or music, audible
to a room full of people instead of to just yourself you must use what is
called a loud speaker. In its simplest form this consists of a metal cone
like a megaphone to which is fitted a telephone receiver.

About Transmitting Stations--Getting Your License.--If you are going
to install a wireless sending apparatus, either telegraphic or telephonic,
you will have to secure a government license for which no fee or
charge of any kind is made. There are three classes of licenses issued to
amateurs who want to operate transmitting stations and these are: (1)
the restricted amateur license, (2) the general amateur license, and (3)
the special amateur license.
If you are going to set up a transmitter within five nautical miles of any
naval wireless station then you will have to get a restricted amateur
license which limits the current you use to half a kilowatt [Footnote: A
Kilowatt is 1,000 watts. There are 746 watts in a horsepower.] and the
wave length you send out to 200 meters. Should you live outside of the
five-mile range of a