-iT\CK
ANKEX
CT
RADIO t RAFT
Booklet No. 1
Miidel Illustrating Arrangement o1 Radio Kfffi\ inu Set.
Handcraft Projects for School antl Home Shops
RADIO CRAFT
(Radio Booklet No. 1)
FRANK I. SOLAR
Nortliorn lliuh Stiiool, Detroit, Michigan.
Editor of "Tool Craft, roys and Useful Articles a Buy Can Make.'
"Practical Construction Work for Home and School Shops,"
"Bird Housts uf Simplt- Constiuction"
The liriice I'lihlishing Company,
Milwaukee, Wisconsin.
Cupyiight 1S)22
The Bi-uce Publishing Company
Printed in V. S. A.
TABLE OF CONTENTS
Radio Sets as Manual Trainin.u- Prujects 7
Eadio Craft 9
The Aerial 13
Tuning Coil No. 1 Ki
Plate of Tuning Coil No. 1 IT
Tuning Coil No. 2 18
Plato of Tuning Coil No. 2 19
Making the Condenser 20
Plate of the Condenser 21
Making a Detector 22
Plate of a Detector 23
Receiving Transformer or Loose Coupler 24
Plate of Receiving Transformer 2.t
Hook Ups for Coils and Coupler 2S
Plate of Hook Ups and Coupler 29
2065680
RADIO SETS AS MANUAL TRAINING PROJECTS
The making: of toys, boats, bird houses, kites and
aeroplanes have all been accepted in turn with great
enthusiasm by boys in manual training classes. Noth-
ing however, like the Radio Craze has ever caused the
boys to beg to come in and work, the girls to inquire if
it would be possible for them to do work, and fathers
and mothers, to come to our shops for parts and infor-
mation, for setting up Radio receiving sets.
Most of the projects made in our shops such as book
racks, etc., will serve the purpose if H-inch longer or
shorter than the drawing. This is not true with the
wireless receiving set, which requires less material than
the usual models, but each part must be a certain size
to make the next part work, and the boy appreciates
the meaning of real accuracy. It also instills in him a
desire to search the shelves of the public library and to
study books on this subject. It makes him rack his
brain to figure out how to make use of available sci'ap
material to take the place of parts that he has not the
money to purchase.
The crowning feature, however, of this project is
that when finished it looks so different from the usual
article the boy brings home, almost like an infernal ma-
chine, that the whole family is interested to the extent
of offering their help to get the thing rigged up for a
tryout. This is so different from the usual interest
shown when the boy's work is brought home, which con-
sists of an expression — isn't it nice. Then the article
is forgotten.
The boy has a chance to tinker with the elements and
with many different kinds of materials. This is the best
kind of education, and the desire for learning comes
from within. It is a chance for father and son to get
together and work on a problem that is of interest to
both.
Let the boys experiment, for it will drive them off
the streets into the school and home work shops where
ever.v boy and man should spend some of his spare time.
While there he will make articles that will not only
afford pleasure and pastime but will be a benefit edu-
cationall.v to the household. Let the good work go on.
F. I. S.
RADIO CRAFT
lllustratiun 1. Tunini.'' Coil. See page Ifi.
RADIO CRAFT
Radio and wireless experinientins' by amateurs in
this country had gotten nicely underway about the time
the World war started. Due to the fact that war de-
partment reg'ulations required aerials to be disman-
tled, amateurs had to lay aside their equipment for
a while. However, after peace was declared experi-
menting' soon became popular again. After the special
training received in service many more young people
were interested and had considerable more practical and
theoretical knowledge of the work than those interested
before the war.
The average person was not any more interested in
Radio, than in any other new feature brought to his
attention. The reason for this was that most broad-
casting was done in code, and it is a considerable task
to master the code so one can receive. And even for
those who could receive, the information gained, was
of little interest.
When different agencies began broadcasting music,
entertainments, lectures, news, etc., to be heard by the
aid of the radio-phone, everyone became interested.
And today we have thousands of people all over the
world enjoying entertainments daily.
There are no laws governing the use of receiving sets
and the handy person can make one that will receive
the broadcasting in his vicinity. The sending, how-
ever, requires an expensive apparatus and also a license,
the obtaining of which involves certain qualifications
and requirements. This is of little concern to most
people as they are content to listen to others of interest
rather than spend their time jamming the air.
Almost any of the apparatus used for broadcasting
and receiving can be made or assembled by the handy
man, boy and mechanic. Although material required is
quite expensive for the larger outfits, the average ex-
pert worker, even if competent to make a set, could
not afford to invest a great amount in material. Per-
sons who can afford to will no doubt buy a complete set,
and even if they were capable would not have the time
to make their own sets. There are thousands of people
who would like to listen in on the programs offered.
They would like to make their own outfits and can do so
by following the directions given in the following pages.
The following drawings and instructions are given to
be used by the handv man and boy in the home and
school shops. It is not intended to give any technical
discussion in this description but to show by drawings
and a brief explanation how to set up a receiving outfit
at a minimum cost. This set is similar to many that
my boys have already made. By the aid of such sets
they are receiving gi-eat enjoyment listening to the code
and the wondei-ful programs they are able to get.
10
RADIO CRAFT
One of these little receiving sets will be worth a
great deal to the busy mother unable to leave home
evenings, to crippled people confined to their beds or
chairs, to convalescents, and people living far out in
the country and at resorts in the summer time.
Do not be misled by statements that for a dollar or
two you can make a set that can be connected to your
victrola and heard all over the house, or that will re-
ceive concerts broadcast at a great distance. This is
not true. To do this requires a set composed of at least
the following equipment, in addition to the receivers
and aerial : a rheostat, amplifier panel, bulb, grid con-
denser, grid leak, six volt (A) battery and a (B) bat-
tery. An outfit of this kind costs $65 and up.
The wireless and radio-phone are still in an experi-
mental stage and it is advisable to investigate and pick
a reliable standard set rather than to invest consider-
able money in inferior wireless apparatus. In a short
time marvelous new equipment will be on the market
and an outfit may be hooked to the electric circuit and
even the ordinary telephone may be used to receive
broadcasting. It would be well woith while for those
interested in this new venture to make a home made
receiving- set first and do a little experimenting until
they decide on the larger set they want. Most of this
beginning apparatus can later be hooked in with the
more expensive set.
lllustratiun
.\ I'lirlabk- Hume .\lLide Outfit.
RADIO CRAFT
11
Illustration 3. A Pocket Outfit.
Illustration 4. A Tuning Coil and the Boy \\'ho Made It.
12
RADIO CRAFT
Illustration 5. Home Mr.de Loose Couplers, Condenser. Detector .thH Coil Wound on Nails.
THE AERIAL
The first thiiiK to be cun.sidered when installing a
receiving set is the aerial. Of course it is possible to
get results from your bed spring's, the eaves trough, a
metal railing and many other things, but natuially a
specially erected aer'al is the most satisfactory.
A loop aerial may be erected indoors. It may be
stretched in the attic or any room. Some have .strung'
the aerial across the room from the picture molding on
one side to the molding on the other. A row of picture
hooks or sci-ew eyes will do to support it. While it is up
out of the way it is not very convenient on house clean-
ing day. Two coat hangers hunLi' at either end of the
room will make good stretchers.
Sound waves travel through the ether and are caught
by the antenna of the aerial, which is the part sus-
pended between the stretchers.
Almost any length of aerial at any height from the
ground will give results for receiving from a short
distance. The higher from the .uround and the longer
the antenna the better.
Excellent results will be obtained by a 7.5 to 1.50 f<iot
aerial placed from 30 to .50 feet from the ground. The
antenna should be allowed to sag a little so it can blow
in the breeze and thus shake off the snow and ice which
might collect and break it if strung tight.
For small sets to receive from a short distance any
kind of wire will do, either bare or insulated. The best
wire to use is No. 14 copper or aluminum (bare). For
guy wii-es use No. 10 or 12 telephone wire.
The laws require that amateurs send on not over a
200 meter wave length. The four wire aerial, illus-
trated in Fig. 1 is 7.5 or 80 feet long, and is about right
for sending this length wave. The masts which are
fastened and braced to the peaks of the roof may be
any length. The stretchers should be about nme feet
long and the wires equally spaced. At the free end M
the wires may or may not be connected with each other.
The other end N, from which the lead in is taken, should
have each wire of the antenna connected to one that
leads in to the instrument.
Fig. 2 shows a short one wire aerial having the
masts fastened to the front and back of the house. Fig.
3 shows bicycle rims or barrel hoops used, where it is
not convenient to get long stretchers.
Fig. 4 is an aerial stretched from a house to a garage
and Fig. 5 shows one wired to chimneys on an apart-
ment building.
Fig. 6 illustrates, at A and B, how ordinary porce-
lain cleats or glass pony insulators are used where the
antenna is connected to the spreaders. The one wire
aerial insulated, as shown in Fig. 7, is made as long as
13
14
RADIO CRAFT
possibk' and is the easiest to erect and will j;ivo good
results. The loose ends can be attached to screw eyes
screwed at any convenient place from the house to the
barn, a tree, post or the garage.
A lightning switch, if large enough to be of any
account, is rather expensive. A drawing for one that
can be made from Vg-inch or thicker sheet copper, and
a cement base is given in lUus. 1. A box of wood can
be made into which to pour the cement. Pegs should
be insei'ted in the cement while soft and jiulled out
after it has hardened to make holes for fastening to
the window sill. The posts can be held in place by a
piece of stick suspended over the top of the box while
the cement is hardening. To conform to wiring regu-
lations it will be necessary to place a plate of composi-
tion material beneath the cement.
A porcelain, glass or rubber tube may be used to
insulate the lead in wire where it passes through the
sash.
RADIO CRAFT
15
RADIO AERIAL
LiaHTNiNG Switch
Fia 3
, Bicycle Rims
OR
Barrel Hoops
ferf
O^
Details of Aerial and Suggestive Methods »»f Mounting.
TUNINC; (OIL No. 1
The radio waves are sent out in different lengths by
different broadcastinj;: stations. The ones you wish to
receive must be tuned in so you can receive them. This
is accomplished by moving the sliders on the sliding
rods.
This outfit is made up complete so that by connecting
your aerial at A your ground at B and your phones at
G and H you are ready to tune in and receive.
The coil can be wound on either a cardboard tube or
a solid piece of wood. If w-ood is used be sure it is
well seasoned or it will shrink and your wire will hang
loose on it.
The first thing to make is the coil. For this get a
rolling pin and saw off the handles. To hold one-half
pound of wire it should be 2% inches in diameter and
10^4 inches long. Make a groove with the marking gauge
iV.-inch from one end. Drive a brad alongside the
groove and then give that end of the pin a coat of
shellac. We are going to make the coil by winding No.
22 enameled copper wire around the pin. Twist the wire
around the nail twice, about 6 inches from the end of
the wire. This end is left for making a connection.
Now wind around the pin, the first time around running
the wire in the groove. This is done while the shellac
is wet and it will help hold the wire in place when it
dries. 11' you shellac as you wind, it will not be neces-
sary to get the shellac on your hands. When you have
reached the other end of the pin drive another brad and
fasten the wire as before but the six inches at this
end should be wound around a pencil making a pig
tail. This end has no connection.
lUustration 6. Winding a Coil.
16
RADIO CRAFT
17
M- Ca T \NhI5KER
N- Crystal cup
O- TiGiiTNiNc Screw
P' CRYSTAL
u
-/2-
TUNINGCOIL No. I.
■^PouND No SB Enamel £0
Copper Wire- Bare
Rolling Pin
Slider
L J L J
-iir
:ir..,
^^rFI
Base
Plan For v^/ring
RIAL iCoNDEHSER 4 Sliders
Z Detector SPisTail
i Slider Roos
^ 3 4 c
Details of Tuning Coil No. 1.
18
RADIO CRAFT
Lay the coil aside and niakp the ends. Fasten them to
the coil with screws about IV2 inches from the top of the
end pieces. Next make the base and fasten to the end
pieces and then the legs and fasten them to the base.
Now if you wish to purchase your parts, buy two
A-inch square brass slider rods and sliders to fit. Also
a condenser and a detector. If you wish to make all
parts, information for makinp them can be had from
following drawings.
Your connections can be made at the end of the
slider rods by fastening the wires under the brass round
head screws that hold the slider rods in place.
Now we shall wire the tuning coil. Bore holes for the
binding posts at A and B and also for the wires that
are connected to them. Connect straight wire left at
the end of the coil to A, after running it through the
hole in the end piece and scraping off the insulation to
make a good connection. Connect wire to the end of
the slider rod at C, run through the hole in the base,
across underneath the base, up through the hole at the
opposite end and through the one in the end and con-
nect to B. Connect a wire to post G on the condenser
and run through holes to post B. Connect H on the
condenser to F on the detector. Connect E the crystal
cup screw with slider rod D.
The cat whisker of the detector is lettered M, the
crystal P, the crystal cup N and the set screw O.
The wood work on this instrument should be stained
and shellaced or varnished to add to its appearance.
Scrape the enamel from the wire where the points of
the sliders touch. Be sure all connections are well made
and no insulation is left between them.
This instrument is ready for use.
TUNING COIL NO. 2
This coil has the same capacity as coil No. 1 but can
be made much cheaper as the wire is the only thing that
need be purchased .
An ordinary oat meal or cereal box is used in place
of the rolling pin on which to wind the coil. Be sure
that the cereal box is dry and give it a coat of shellac
to stiffen it. If the coil is wound on a damp box, the
wire will come loose when the box dries out.
Begin work on this instrument by making and wind-
ing the coil. The top and bottom of the box are re-
moved and wooden discs are tacked in the ends of the
tube. The discs can be sawed to shape with a coping
saw.
Make the wood frame for holding the coil. This needs
no further explanation, as the construction and sizes
of different parts can be learned from the drawing.
RADIO CRAFT
19
Tuning coil No.i.
This coil isCapable Of receiving a 5
WELL A3 No.i But As No rods. Sliders Or
Posts Are used only viire need Be Purchased
No 14 COPPER WIRE
r-TA K£ Two
Details for Making Tuning Coil No.
20
RADIO CRAFT
The sliders are made of wire and slide lui tlie wooden
frames connected to the uprights at the ends. This
saves the expense of slider rods, etc.
The windin,?: of the coil and the wirin."- of this instru-
ment are the same as explained for Coil No. 1.
Screw eyes and rubber bands should be adjusted, as
shown on the drawing, at both ends of the instrument.
The rubber bands hold the points of the sliders in
close contact to the coil. Scrape the insulation where
the sliders touch the coil, as instructed for Coil No. 1.
The instrument should be stained and shellaced or
varnished to add to its appearance.
Instead of hooking to the end of the slider rod, as
instructed for Coil No. 1, on this coil hook to the eye in
the slider itself.
MAKIN(; THE CONDENSER
It is the practice in connecting up receiving sets to
use a small fixed condenser across the telephone ter-
minals. The condenser acts as a stopping condenser.
In small set hook ups some are able to get results with-
out the condenser.
Materials needed for the condenser are as follows:
1 Piece of wood, % x^Vi x 6 inches.
2 Pieces of Cardboard, 3V4 x5% inches.
10 Sheets of tin foil, 3x4y2 inches.
11 Pieces of waxed paper, .3'4 x4 inches.
2 Binding posts.
4 Pieces of thin sheet brass.
Some vaseline.
Begin making the condenser by cutting 11 pieces ol
waxed paper according to pattern C.
Next cut ten pieces of tin foil according to pattern B
and two pieces of cardboard like pattern A.
Place a piece of cardboard A on the table and with
the fingers spread on the upper face a thin covering
of vaseline, .just enough to hold the first sheet of waxed
paper in place. Lay the first sheet of waxed paper C.
on the cardboard and grease the upper side as you did
the cardboard. Now place the first sheet of tin foil on
the waxed paper, with the %" x %" projection, ex-
tending at one end. Continue piling up the pieces as
indicated on the drawing. The next piece of tin foil
should have %" x %" projection, extending at the oppo-
site end. Continue greasing and piling the parts, being
sure to alternate the projection on the tin foil sheets.
Cut the thin sheet brass washers and put in place.
iVIake the wooden base and bore holes for the binding
posts.
Place the condenser on the wood, after it has been
pressed together tightly. Locate and bore holes. As-
semble according to the drawing ready for connecting
to the set.
If desired the condenser may be connected directly
to the base of the tuning coil instead of attaching to the
wooden base.
In the corner of the drawing will be found pictures
of commercial condensers, that can be purchased for
from 30c to $1, depending on the workmanship.
RAniO CRAFT
21
4 A__
B -■ :-,
B -
B — =
fl — —
c
VJaxed Paper
Bread Wrapper
'^
Condenser
Nut ^^,
t 3"
Dt-tails uf a Hume Made L'undenser.
MAKING A DETECTOR
The sound waves as they are eauR-ht by the antenna
are not of a desirable type of current. They must be
changed to the suitable type and this is done by the
detector.
The materials used for the commercial product con-
sist of a wooden base, two binding posts, a crystal cup
and a part called a cat whisker, which is nothing more
than a pig tail made of bronze spring \vire. The pig
tail is made by winding the wire around a finishing
nail.
The crystal is nothing more than lead sulphite and
may be called galena, carborundum, silicon, etc. This
mineral must be chipped off to make a bright surface
and a good contact with the cat whisker. Dust soon
gathers on the surface of the crystal. This can be pre-
vented by covering the whole detector with a large
drinking goblet or wooden box.
Practically every home made detector is made in a
different way and of different materials. The reason
for this is that there are only two essential points;
first some means of holding the cat whisker so it can be
moved about and adjusted on the crystal; and second
some means of holding the crystal tightly.
The detector can be set up on a special base or on
the base of the tuning coil.
For Type 1 get a piece of wood %" x 214" x 4I/2",
an old cuff or suspender clip, a piece of sheet brass, five
round head bi'ass screws and a piece of fine brass or
bronze spring wire. Bend the clip and brass strip to
form, as indicated on the drawing, and drill holes for
the screws. If the hole for the cat whisker screw is
made smaller than the size of the screw the screw when
forced through the hole will tap out the hole. Assemble
the parts, solder the cat whisker to the screw and a wing-
in the slot in the head of the screw. Insert the crystal
in clip, and tlii' detector is ready fur business.
Type 2 is made similar to Type 1, except that all
parts may be purchased and only the assembling is to
be done. The conni'ctions in this case are made betvvi'en
the nuts at J.
The adjustment and sensitiveness of the detector
are responsible for the success of your set. So it is
quite important that you buy a good piece of tested
mineral or crystal.
Be sure when making connections antl before sol-
dering any joints that all parts are well scraped.
Not scraping off the insulation is often the cause of
poor results.
22
RADIO CRAFT
23
DETECTOR
Type /
Type 2
CUFF CL IP
V
B
^
^
J
i
^-^
4 -
F
tniflO
Commercial Type
F
£
.J^
/^
Boy OF GALENA
/^- Wood
B- No 36 Bra 35 Spring Wipe
C- Galena
D- Sheet Brass
E- Heavy Copper vjire
f- Bin DING Post
G-Galena Cup
h-Set Screw
J- Brass Stove Bol t ^Nuts
Details for the Conbtrucliun of a Detector.
RECEIVING TRANSFORMER OR LOOSE COUPLER
A loose coupler is more difficult to make than a tuning
coil but it will give better results.
It is for the same purpose as the coil, i. e., to tunc
in the sound waves.
With this coupler, a good detector, a sensitive piece
of galena, a pair of 2,000 ohm receivers, 100 feet of
copper antenna well insulated suspended on an aerial
50 feet from the ground an operator should be able to
receive from 200 to 300 miles.
The coupler is composed of two tubes both wounil
with wire, one sliding inside of the other. The larger
tube is called the primary and the smaller the secon-
dary. The primary is set to the wave length by adjust-
ing the top slider. Then the switch on the secondary and
the coupler (drawing the secondary in and out on the
rods) are manipulated until the loudest sound is heard.
If you do not possess many tools and it would be
difficult for you to make the box it need not all be made.
The only parts needed are the bottom and the two ends.
For the tubes get an oatmeal or other cereal box for
the primai-y and a salt box for the secondary. Be sure
they are dry before winding the wire on them, so they
will not dry out and shrink after being wound. It will
stiffen the cardboard to shellac it well before using.
With a coping saw, cut the opening in the front piece
and then make %" discs according to the drawing to fit
the back of the primary and both ends of the secondary,
also a Vi" disc to fasten to the front of the secondary.
Get a w." sliding curtain rod, that is one that has a
tin tube in which the solid rod slides. Cut off two pieces
of each tube and rod the length of the box. The tubes
are to be inserted in the ends of the secondary and the
solid rods are to be filed square and to a point and
driven in holes throu.;h the disc in the back of the
primary and into the back of the box.
Wind the prnnary with No. 24 cotton covered copper
wire and when finished give it a good coat of shellac.
It will take about one quarter of a pound. Start Vu"
from the end of the box. Fasten the ends by punching
small holes in the cereal box and threading the end of
the wire into the box. The wire at the back end should
be twisted so it will not come loose; but the one at the
front end should be left quite long, as it is to be
threaded back through the box and out at the back end
where it is fastened to the binding post (X).
When the primary is wound it should be tacked with
•■■" brads to the disc at the back and to the circumfer-
ence of the hole cut in the front piece.
24
RADIO CRAFT
25
Receiving Transformer
OR
LOOSE COUPLER
SLIDING CURTA<.\
ROD AND TUBE
Details, for Makinu a Loo!>f Coupler and Picture of Commercial Type.
26
RADIO CRAFT
Purchase or make a slider, and also get a i',-. " slider
rod 6^4" long. Fasten the rod to the top of the box as
indicated and connect it to a binding: post at Z with a
piece of insulated wire having one end turned under
the screw at Y.
Now we shall wind the secondary. For the secondary
we need about one quarter pound of No. 30 silk covered
copper wire, a rotary lever switch, twelve V*" taps or
brass headed tacks and two pieces of flexible copper
wire, each 18" lonir. Silk covered electric light cord
will do for the flexible wire.
Along the top of the secondary, divide off' the space
into twelve parts and at each division punch a hole
with a darning needle. Start about '^ inch from
the end to make the divisions and end about th's
distance from the other end. Start winding by thread-
ing the end of the wire through the first hole No. 1 at
the back end of the secondary. Scrape the end of this
wire and solder it to one end of one of the pieces of
flexible wire. This flexible wire is to be threaded out of
the tube through hole A when this front disc is finally
fastened in place. Start now and wind until the wire
comes to the center of the next hole. {Do not cut the
wire but make a long loop tliut irill reach two inches
out of the front of the tube) thread through hole No. 2.
Contimic to wind and loop through holes until hole 12
is reached.
Now scratch the insulation off" of the wire at the end
of each loop and fasten under the nut of the taps or
solder to the ends of brass-headed tacks, if they are used
for taps. Of course the location of the taps must be
spaced off on the front disk of the secondary and holes
bored for them, and also for the switch. Fasten one
end of the other flexible wire to the switch post inside
the tube and thread out with the other flexible wii-e
through hole A. Now place the front head in the tube
and fasten with '4" round head screws so it can be
easily removed if repairs have to be made to the wires
inside of the tube.
Scratch the insulation off the wire coil on tlic pri-
mary, directly under the slider rod so that the slider
will make a good contact. The tongue of the slider will
have to be bent no doubt to the proper shape.
For the hook up look at the diagram on the sheet of
hook ups.
Z is connected to the aerial, X is connected to the
ground, the switch of the secondary to the condenser
and the other flexible wire from hole 1 to the detector.
To improve the looks of your instrument stain ma-
hogany, varnish and rub down or enamel it black.
RADIO CRAFT
27
Illustration 7. Kadio Apparatus Made by Boys Under the Author's Direction and Successfully Used.
HOOK UPS FOR COILS AND COUPLER
The term hook up is one used commonly by radio
operators and means the method of wiring the pieces
of apparatus together to mal<e up a set.
There are many different ways of wiring or connect-
ing the instruments together to get results and little
difference can be noticed by the different methods. So
if by chance you connect your set differently from the
diagrams given on the drawini;- you may get just as
good results.
We shall trace the hook up in Fig. 1. The aerial A is
connected to the lightning switch at the center post B
by the lead in wire, X. If you cannot afford a lightning
switch, arrange your lead-in wire so it can be discon-
nected from the post B, fastened to an iron weight and
swung at least 6 feet away from the house to the
ground when not in use. If you have a switch connect
the ground post C by a piece of No. (! wire to a piece
of gas pipe, driven into the ground. When not in use
throw your switch to this post C.
Connect post D with the end of your coil wire E.
The other end of your coil wire is pig tailed and has
no connection, as F. Connect H to your water faucet,
a radiator, or a wire run to a pipe driven in the ground
at G. Also connect one post of your condenser .1 to
your ground wire G. Connect the other post E of your
condenser to post L of your detector N. Now connect
post N of your detector to post O the end of the other
slider rod and your circuit is made.
The terminal of your receivers should be hooked to
the binding posts at K and J on the condenser.
Receivers are made in different types. A commonly
used kind is the ordinary telephone receiver which is
about 75 or 80 ohms. This type is not very satisfactory
because it must be held by the hand while receiving.
The amateur one-part head piece, which is also about
7.') ohms, just brings the message to one ear and allows
surrounding sounds to go to the other. The two part
head set of from 2,000 to 3,000 ohms is very satisfac-
tory. A 2,000 ohm head piece means that each part is
a 1,000 ohm unit.
Fig. 2 shows another hook up for the tuning coil
and can be easily traced after reading the description
for Fig. 1.
Fig. o is a book u|) foi- the loose coupicf. The
aerial in this case is connected with the slidi r II. The
front end of the pi'imarv wire P is connected to ground
G. The switch Q is connected with flexible wire to the
post R of the condenser I. The post S of condenser is
connected to post T of detector. The post U of the de-
tector is connected with flexible wire fastened to the
end of the wire at the back end of the secondary \V.
Y is the primary.
28
IIADIO CRAFT
29
Aic«,
HOOK UPS FOR COILS AND COUPLER
Fig. I
Slid£R
I g = ffoo
na. 3.
Coil
1^
I ? ^
Fiat-
A -AERIAL
X- Lead In
G-Grouno
M' Detector
I - Condenser
Y' Primary
\N- Secondary
Q^ Switch
Head Set Receivers
Diagrams lur Hook Ups
30
RADIO CliAFT
Illustration 8.
Even the Doll May Share the Evening's Broadcastinjf.
Illustration 9.
Making: Work a Plt-asuri' with the Radiophone.
UNIVERSITY OF CALIFORNIA LIBRARY
Los Angeles
This book is DUE on the last date stamped below.
HEPDID-UW:
NOV 2 4 1986
B 000 003 233 4
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