San Antonio light. [volume] (San Antonio, Tex.) 1911-1993, 1925-10-25
BOT TIES USED
As WINDING.
FORMS
Low Loss Tuner and Aerial
Coil Need Cost Expert
menter Little.

So great has been the demand in
San Antonio for the radio parts, as a
result of the articles published in The
Sunday Light on home construction,
that many would-be radio builders
have been forced to delay their manu-
facture of the Browning Drake radio
receiver which The Light has recon-
mended.
1t has been particularly difficult
to obtain the coils and tuning units
which the designers of the set worked
out as particularly adapted for this
lookup. There is no reason, how
ever, why these coils should not be
made at home, and The Sunday Light
herewith publishes directions for max
ing them.
All that is required for making the
coils, aside from the wire with which
they are wound and a few incidental
pieces of hardware which will be
found in the average mans home
workshop, is the purchase OF. four
strips of hard rubber, or bakelite
a short section Of rubber or fiber tub
ing.
USE OLD PANEL.
II the builder has a spoiled or dis
carded radio panel about the place,
the strips may easily be cut from it
with a hacksaw. Otherwise he will
have to buy a piece of hard rubber
large enough to be cut into the requi'
site pieces.
Cut two strips 31-4 inches long
and half an inch wide. The thick
ness will depend on that of the panel
from which they are cut, and is not
important. These are for mounting
the primary coil.
Cut third strip AS inches by
IL inch; cut a fourth 4 3-S inches
long. These are for the three cir
cult tuner.
A quarter Of an inch from the end
Of each of these bore hole large
enough to take small nut and bolt
"a 6-32 bolt. or smaller, will do.
About half an inch further in on both
strips bore n similar hole. These
holes will take bolts which serve to
held the mounting. together and also
MS terminals for the ticker leads OF
the tuner.
Measuring still on both strips To-
inches from the bored end and cut
holes through them slightly more than
a quarter of an inch in diameter, to
accommodate the ticker shaft. A
glance at the diagram will show what
we are driving at.
USE FOR OLD BOTTLES.
Taking the longer strip, bore an
other small hole three-eighths Of an
inch from the end which as yet has
been untouched. and countersink it
on one side. The shorter strip takes
a hole likewise, three-eighths Of an
inch from the unbored end.
Now look around the house for two
bottles-empty. They should be APP
proximately three inches in diameter,
although a slight variation will not
make an important difference. Now
cut four pieces OF surgeons tape,
about seven inches long and half an
inch wide. Lay these lengthwise
along one bottle sticky side up. and
space them equally distant around the
circumference. Now take a spool OF
No. 20 double cotton covered wire,
which may be bought in any radio
shop, and wind on, tightly % turns.
Twist the wire into a tiny loop. Then
wind on % more turns. Turn up the
ends of the adhesive tape and fold
them over on the coil, holding the
turns in place. Now paint the entire
coil lightly with collodion, and set
aside tn dry. Do not use more col
lodion than is necessary to bind the
wires tightly to each other. This is
the antenna coil.
When the collodion IL dry remove
the coil, breaking the bottle with a
hammer IL necessary, and mount the
coil between the two hard rubber
strips as shown in the diagram.
MAKING TUNER.
On the other bottle wind the sec
ondary Of the three,circuit tuner, put
ting on 78 turns of No. 20 double cot
ton covered wire, and making small
loop Just as in the first coil, but this
time on the eighteenth turn from the
bottom Of the secondary. After this
coil is dry and off the bottle form.
cut small disk of wood about half
an inch thick. and a trifle smaller
than the diameter of the coll, so that
it will slip into the bottom as shown.
Cut a slot around the circumference OF
this disk and in it wind 26 turns of
No, 20 wire, or as near that size as
YOU can obtain. This is the primary
of the three-circuit tuner, and fits
into the coil, to be secured with wood
screws and angle braces as the dia-
gram shows plainly.
Now for the ticker. You will need
a piece OF fiber or hard rubber tubing
two and one-half inches in diameter.
On this wind 20 turns of No. Is d. C.
c. wire, splitting the winding in the
middles far enough apart to allow the
ticker shaft to pass through. The
shaft is brass or copper rod one
quarter Of an inch in diameter or less.
The assembly of the tuner, using
the hard rubber strips and the other
parts described is plainly shown in the
drawing. The end of the secondary
nearest the ticker should be connect
ed 10 the grid Of the detector tube; the
bottom Of the secondary to filament
plus the start of the primary (near-
est the ticklcr) TO Amplifier Il plus
binding post of the set, and the bot
tom of the primary to p on the radio
frequency tube. The set is wired ex-
actiy as with the standard Browning
Drake parts. These coils, being al
most entirely air wound, are low loss,
and will be found to tune sharply.
They must be mounted in the set
with their axes ut right anglcs-that
is, the antenna coil vertically and the
secondary in a horizontal position, to
avoid feed back.