Atlanta tri-weekly journal. [volume] (Atlanta, Ga.) 1920-19??, 1922-04-25
HOW To CONSTRUCT
INEXPENSIVE SET.

dio units in the market, due to the
inability of the manufacturers to
supply the ever-increasing demand
for their wares, has forced thou
sands of wireless devotees to assem-
BILE their own instruments, picking
up a piece here and there until the
unit is complete. Much has been
written and more has been said con-
corning the assembling at home of
the receiving instrument. Some,
paving particular attention to the
performance of the instrument and
losing sight of the cost, have put
the instrument in the class of pro-
hibitive things as far as the pocket
books of most of us are concerned,
while others have sacrificed every
thing to cheapness and consequently
the assemblage Is very poor in ev-
cry respect.
The instrument to be described in
this and subsequent articles is one
that equals the performance OF in
struments that cost two and three
times as much and can be built by
anybody and made to operate per-
fectly if directions are followed. The
inductive coupling and it's construc-
ton is the object of this article.
The tuning device or inductive
coupling in this set is made in the
form of three lattice work spider
coils. "P" represents the primary
coil, IS" the secondary and "T'' the
ticker. Both the ticker and secon-
dairy coils are adjustable, the pri-
mary coil being stationary. With
this type of instrument the finest de-
gree Of adjustment and tuning is
possible. These coils are made in
the following way. From a sheet
of 1-16-inch pressed fiber cut a disc
3 IL inches in diameter. Mark Off
the circumference in thirty equal dl-
visions and cut out as indicated in
illustration "a" removing the shad-
ed parts, leaving fifteen spoke-llke
sections. A small hole about liz
inch, should be made in the center
of the disc and two other holes large
enough to permit the passage of
1-4-inch brass rod with ease. These
two holes should be made IL inch
on both sides Of the center. 1t is
through these holes that the guide
and support rods are placed, on
which the secondary and ticker COILS
slide back and forth for tuning and
adjustment purposes.
On these fiber forms are wound
in a counter clock-wise direction No.
"a enameled copper wire. The pri-
mary coil having % turns, the sec
ondary, "a, and the ticker 20. Start
at the base Of the spokes to wind
the wire as directed. In front OF the
third and behind the fourth and so
on until the three coils are made.
So that no mistake is likely to be
made in mounting the coils it is well
to mark the front of the coils In
some permanent way so that they
can all be faced in the same direction
when assembled. When you have
finished you will have IA turns of
wire on either side of the Up" coil,
IL turns on the $50 and 10 on the
"T" coils. It Is absolutely essen
tial that the wire be put on the
coils in the same direction or they
will be useless. Always leave about
six inches of wire at the beginning
and at the end of each coil so that
it can be conveniently connected to
it's proper binding post.
The mounting for the coils is very
simple in design ana is nothing more
than a box measuring IL 1-3 inches
long, seven inches high and four
inches wide. In the ends are three
holes corresponding to the holes in
the discs. The material is good
dry wood such as can be obtained
from any grocery box.
To the center of the ticker and
secondary coils are attached brass
bushings 8 IA inches in length by
means Of a bolt and washer. The
bushing should be made to fit the
threaded brass rod and operate cas-
lily because it is by means of this
threaded rod that the adjustments
are made.
Now we are ready to assemble the
unit. Through the two outer holes
of all three discs run the two brass
rods which act as the guides and
supports and mount them in the
holes in the end pieces of the box.
Then take the two brass threaded
rods to the ends of which have been
attached the two PANEL knobs, and
pass them through the ends of the
box and screw them into the brass
bushings. BY turning the knobs it
is now possible to draw the "T'' and
rs" coils away from the up" coil and
by reversing the operation the coils
will be pushed toward the Up" coil.
This procedure will give the finest
degree of tuning when the unit is
put in operation.
On top of the wooden frame work
are mounted the six binding posts in
three groups. The loose ends of the
wires are then taken to the posts in
the following order after the ends
of the windings have been scraped
clean of all enamel and the wire is
clean and bare. To the first pair of
posts are taken the ticker coil wires
leaving enough slack in the wires to
allow the coil about three inches
play for adjustment; next the sta
tionary "P" coil ends are attached
to the second pair of binding posts,
the loose ends may here be drawn
tight as there is no motion and last
the secondary's ends are carried to
the last posts, allowing the slackness
of wire for adjustment. After the
instrument has been used and there
is no change necessary the connec-
tons to the binding posts should be
soldered. Do not solder first, as it
is often necessary to make some
minor changes before everything is
operating at it's best.
This is the ideal mounting for
these coils, as it gives the finest de-
gree of tuning and there is no pos
sibility of them moving after adjust