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 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.]
The _leading-in wire_, that is, the wire that leads from and joins the
aerial wire with your sending and receiving set, can be connected to
the aerial anywhere it is most convenient to do so, but the best
results are had when it is connected to one end as shown at A in Fig.
4, in which case it is called an _inverted L aerial_, or when it is
connected to it at the middle as shown at B, when it is called a _T
aerial_. The leading-in wire must be carefully insulated from the
outside of the building and also where it passes through it to the
inside. This is done by means of an insulating tube known as a
_leading-in insulator_, or _bulkhead insulator_ as it is sometimes
called.
[Illustration: (A) Fig. 4.--Inverted L Aerial.]
[Illustration: (B) Fig. 4.--T Aerial.]
As a protection against lightning burning out your instruments you can
use either: (1) an _air-gap lightning arrester,_ (2) a _vacuum tube
protector_, or (3) a _lightning switch_, which is better. Whichever
of these devices is used it is connected in between the aerial and an
outside ground wire so that a direct circuit to the earth will be
provided at all times except when you are sending or receiving. So
your aerial instead of being a menace really acts during an electrical
storm like a lightning rod and it is therefore a real protection. The
air-gap and vacuum tube lightning arresters are little devices that
can be used only where you are going to receive, while the lightning
switch must be used where you are going to send; indeed, in some
localities the _Fire Underwriters_ require a large lightning switch to
be used for receiving sets as well as sending sets.
How to Put Up a Cheap Receiving Aerial.--The kind of an aerial wire
system you put up will depend, chiefly, on two things, and these are:
(1) your pocketbook, and (2) the place where you live.
A Single Wire Aerial.--This is the simplest and cheapest kind of a
receiving aerial that can be put up. The first thing to do is to find
out the length of wire you need by measuring the span between the two
points of support; then add a sufficient length for the leading-in
wire and enough more to connect your receiving set with the radiator
or water pipe.
You can use any size of copper or aluminum wire that is not smaller
than _No. 16 Brown and Sharpe gauge._ When you buy the wire get also
the following material: (1) two _porcelain insulators_ as shown at A
in Fig. 5; (2) three or four _porcelain knob insulators_, see B; (3)
either (a) an _air gap lightning arrester,_ see C, or (b) a _lightning
switch_ see D; (4) a _leading-in porcelain tube insulator,_ see E, and
(5) a _ground clamp_, see F.
[Illustration: Fig. 5.--Material for a Simple Aerial Wire System.]
To make the aerial slip each end of the wire through a hole in each
insulator and twist it fast; next cut off and slip two more pieces of
wire through the other holes in the insulators and twist them fast and
then secure these to the supports at the ends of the building. Take
the piece you are going to use for the leading-in wire, twist it
around the aerial wire and solder it there when it will look like A in
Fig. 6. Now if you intend to use the _air gap lightning arrester_
fasten it to the wall of the building outside of your window, and
bring the leading-in wire from the aerial to the top binding post of
your arrester and keep it clear of everything as shown at B. If your
aerial is on the roof and you have to bring the leading-in wire over
the cornice or around a corner fix a porcelain knob insulator to the
one or the other and fasten the wire to it.
[Illustration: (A) Fig. 6.--Single Wire Aerial for Receiving.]
[Illustration: (B) Fig. 6.--Receiving Aerial with Air Gap Lightning
Arrester.]
[Illustration: (C) Fig. 6.--Aerial with Lightning Switch.]
Next bore a hole through the frame of the window at a point nearest
your receiving set and push a porcelain tube 5/8 inch in diameter and
5 or 6 inches long, through it. Connect a length of wire to the top
post of the arrester or just above it to the wire, run this through
the leading-in insulator and connect it to the slider of your tuning
coil. Screw the end of a piece of heavy copper wire to the lower post
of the arrester and run it to the ground, on porcelain knobs if
necessary, and solder it to an iron rod or pipe which you have driven
into the earth. Finally connect the fixed terminal of your tuning coil
with the water pipe or radiator inside of the house by means of the
ground clamp as shown in the diagrammatic sketch at B in Fig. 6 and
you are ready to tune in.
If you want to use a lightning switch instead of the air-gap arrester
then fasten it to the outside wall instead of the latter and screw the
free end of the leading-in wire from the aerial to the middle post of
it as shown at C in Fig. 6. Run a wire from the top post through the
leading-in insulator and connect it with the slider of your tuning
coil. Next screw one end of a length of heavy copper wire to the lower
post of the aerial switch and run it to an iron pipe in the ground as
described above in connection with the spark-gap lightning arrester;
then connect the fixed terminal of your tuning coil with the radiator
or water pipe and your aerial wire system will be complete as shown at
C in Fig. 6.
A Two-wire Aerial.--An aerial with two wires will give better results
than a single wire and three wires are better than two, but you must
keep them well apart. To put up a two-wire aerial get (1) enough _No.
16_, or preferably _No. 14_, solid or stranded copper or aluminum
wire, (2) four porcelain insulators, see B in Fig. 5, and (3) two
sticks about 1 inch thick, 3 inches wide and 3 or 4 feet long, for the
_spreaders_, and bore 1/8-inch hole through each end of each one. Now
twist the ends of the wires to the insulators and then cut off four
pieces of wire about 6 feet long and run them through the holes in the
wood spreaders. Finally twist the ends of each pair of short wires to
the free ends of the insulators and then twist the free ends of the
wires together.
For the leading-in wire that goes to the lightning switch take two
lengths of wire and twist one end of each one around the aerial wires
and solder them there. Twist the short wire around the long wire and
solder this joint also when the aerial will look like Fig. 7. Bring
the free end of the leading-in wire down to the middle post of the
lightning switch and fasten it there and connect up the receiver to it
and the ground as described under the caption of _A Single Wire
Aerial_.
[Illustration: Fig. 7.--Two Wire Aerial.]
Connecting in the Ground.--If there is a gas or water system or a
steam-heating plant in your house you can make your ground connection
by clamping a ground clamp to the nearest pipe as has been previously
described. Connect a length of bare or insulated copper wire with it
and bring this up to the table on which you have your receiving set.
If there are no grounded pipes available then you will have to make a
good ground which we shall describe presently and lead the ground wire
from your receiving set out of the window and down to it.
How to Put Up a Good Aerial.--While you can use the cheap aerial
already described for a small spark-coil sending set you should have a
better insulated one for a 1/2 or a 1 kilowatt transformer set. The
cost for the materials for a good aerial is small and when properly
made and well insulated it will give results that are all out of
proportion to the cost of it.
An Inexpensive Good Aerial.--A far better aerial, because it is more
highly insulated, can be made by using _midget insulators_ instead of
the porcelain insulators described under the caption of _A Single Wire
Aerial_ and using a small _electrose leading-in insulator_ instead of
the porcelain bushing. This makes a good sending aerial for small sets
as well as a good receiving aerial.
The Best Aerial that Can Be Made.--To make this aerial get the
following material together: (1) enough _stranded or braided wire_ for
three or four lengths of parallel wires, according to the number you
want to use (2) six or eight _electrose ball insulators_, see B, Fig.
8; (3) two 5-inch or 10-inch _electrose strain insulators_, see C; (4)
six or eight _S-hooks_, see D; one large _withe_ with one eye for
middle of end spreader, see E; (6) two smaller _withes_ with one eye
each for end spreader, see E; (7) two still smaller _withes_, with two
eyes each for the ends of the end spreaders, see E (8) two _thimbles_,
see F, for 1/4-inch wire cable; (9) six or eight _hard rubber tubes_
or _bushings_ as shown at G; and (10) two _end spreaders_, see H; one
_middle spreader_, see I; and one _leading-in spreader_, see J.
[Illustration: (A) Fig. 8--Part of a Good Aerial.]
[Illustration: (B) Fig. 8.--The Spreaders.]
For this aerial any one of a number of kinds of wire can be used and
among these are (a) _stranded copper wire;_ (b) _braided copper wire;_
(c) _stranded silicon bronze wire,_ and (d) _stranded phosphor bronze
wire_. Stranded and braided copper wire is very flexible as it is
formed of seven strands of fine wire twisted or braided together and
it is very good for short and light aerials. Silicon bronze wire is
stronger than copper wire and should be used where aerials are more
than 100 feet long, while phosphor bronze wire is the strongest aerial
wire made and is used for high grade aerials by the commercial
companies and the Government for their high-power stations.
The spreaders should be made of spruce, and should be 4 feet 10 inches
long for a three-wire aerial and 7 feet 1 inch long for a four-wire
aerial as the distance between the wires should be about 27 inches.
The end spreaders can be turned cylindrically but it makes a better
looking job if they taper from the middle to the ends. They should be
2-1/4 inches in diameter at the middle and 1-3/4 inches at the ends.
The middle spreader can be cylindrical and 2 inches in diameter. It
must have holes bored through it at equidistant points for the hard
rubber tubes; each of these should be 5/8 inch in diameter and have a
hole 5/32 inch in diameter through it for the aerial wire. The
leading-in spreader is also made of spruce and is 1-1/2 inches square
and 26 inches long. Bore three or four 5/8-inch holes at equidistant
points through this spreader and insert hard rubber tubes in them as
with the middle spreader.
Assembling the Aerial.--Begin by measuring off the length of each wire
to be used and see to it that all of them are of exactly the same
length. Now push the hard rubber insulators through the holes in the
middle spreader and thread the wires through the holes in the
insulators as shown at A in Fig 9.
Next twist the ends of each wire to the rings of the ball insulators
and then put the large withes on the middle of each of the end
spreaders; fix the other withes on the spreaders so that they will be
27 inches apart and fasten the ball insulators to the eyes in the
withes with the S-hooks. Now slip a thimble through the eye of one of
the long strain insulators, thread a length of stranded steel wire 1/4
inch in diameter through it and fasten the ends of it to the eyes in
the withes on the ends of the spreaders.
[Illustration: (A) Fig. 9.--Middle Spreader.]
[Illustration: (B) Fig. 9.--One End of Aerial Complete.]
[Illustration: (C) Fig. 9.--Leading in Spreader.]
Finally fasten a 40-inch length of steel stranded wire to each of the
eyes of the withes on the middle of each of the spreaders, loop the
other end over the thimble and then wrap the end around the wires that
are fixed to the ends of the spreaders. One end of the aerial is shown
complete at B in Fig. 9, and from this you can see exactly how it is
assembled. Now cut off three or four pieces of wire 15 or 20 feet long
and twist and solder each one to one of the aerial wires; then slip
them through the hard rubber tubes in the leading-in spreader, bring
their free ends together as at C and twist and solder them to a length
of wire long enough to reach to your lightning switch or instruments.
Making a Good Ground.--Where you have to make a _ground_ you can do so
either by (1) burying sheets of zinc or copper in the moist earth; (2)
burying a number of wires in the moist earth, or (3) using a
_counterpoise_. To make a ground of the first kind take half a dozen
large sheets of copper or zinc, cut them into strips a foot wide,
solder them all together with other strips and bury them deeply in the
ground.
It is easier to make a wire ground, say of as many or more wires as
you have in your aerial and connect them together with cross wires. To
put such a ground in the earth you will have to use a plow to make the
furrows deep enough to insure them always being moist. In the
counterpoise ground you make up a system of wires exactly like your
aerial, that is, you insulate them just as carefully; then you support
them so that they will be as close to the ground as possible and yet
not touch it or anything else. This and the other two grounds just
described should be placed directly under the aerial wire if the best
results are to be had. In using a counterpoise you must bring the wire
from it up to and through another leading-in insulator to your
instruments.