New-York tribune., 1922-05-21

..sdenser purchaseu' s"o CT" ia0Ae ai
..;.nt radio receiver right at home
.s.t can distinguish between messages
e~.m different transmitting stations
..n. an vsye lengths nearly the same.
rho outdt will enable any one to hear
ado code messages or nsssic and voice
..,. from medium power transmitting
,..,ions within an area about the size
- large city, and from high power
,.ations within so miles, provided the
rsyes used by the sending stations
.sys wave frceuencies between 500 and
1900 kilocyces per second, that is,
vsye lengths between 500 and 200
m.ters. This equipment will not re-
,eiye undamped (continuous) waves.
Thi. set is superior to a single-cir-
,ui. outfit, as it is more selective,
that is, can be tuned sharper. The in
,,rue.ions tell how to make all the
ssrts Of receiving station except the
srtenns, lightning switch and neces-
{ ssry ground connections.
8 Parts of Set
\ The two-circuit receiving set con-
8 'sis.s essentially Of a coupler, a vari-
able conderss-, crystal detector and
scsessories,
Assembled receiving set is shown in
4 figure !. and Figure shows how to
wire the set.
Tie coupler. shown in left half of
Fig. /, is composed of fNad section
nsde up OF the coil tube P. the upright
/ the contact panel X ard the base
B and movable section composed OF
cuil tube s, the supporting contact
PANEL II and the base L,
Instructions for making the movable
col OF the coupler are as follows:
Movable or Secondary Coil
The coil tube s, Fig. 1. Is a piece Of
sssdboard tubing 36s incnes in diam
ter and 4 inches long A round card.
5oard tablcsalt box which can be OBJ
famed al grocery store is about 3ss
inches in diameter and can be used
tMthis purpose. One OF the cardboard
ends or caps should be securely glued
to the boz. This tube il wound with
No. "a or No. 20! double cotton COW
e.ed copper wire
To wind The Wire punch two holes
in the tube s inch from the open end
ss shown at r. FIG. ,. Weave the end
Of the wire through these noles so that
i is firmly anchored and has one end
extending about 10 inches inside the
tube. Punch a hole + about IS inch
from the otncr end (whlcn has the
cardboard cover secured to it) in line
with the holes punched at f. Draw the
free end of the wire through the in
side of the tube and thread it out
through the hole at F. Now wind on
10 turns of wire and take OF Ginch
twisted tap made by twisting 6inch
!oop of wire together at such place
b that ii will be slightly staggered from
the first connection. Hold the turns
tight and punch hole B directly un-
derneath this tap. Insert the end of
the tap in the hole and pull it through
the inside Of the tube 50 that the
turns are held in place. The hole for
this tap should be slightly staggered
from the first two holes which w.arc
punched. Punch another hole L Is inch
+ from the other end OF the sube and in
liue with the hole B. Thread the
twisted tap out through this hole and
pull it tight. Wind on ~ more turns
and bring out another twisted tap,
then 10 more turns and another tap,
10 turns and another tap, 10 more
turns and another tap. Finally, wind
oE 70 more turns and bring out the
free end of the wire in the same man
ner as the taps were brought out. The
tube now has so turns of wire wound
on it and there are twisted taps and
two single wires projecting through
the row of holes at the = sed end of
the tube. The position o1 the wires
inside the coil tube is SHOWN by the
dotted lines.
Base and Support for Coil
The contact panel NJ. Fig. l, which
supports the coil tube, is a piece OF
diy wood q Il inches high, 4 inches
WIDE and 12 inch thick. The contacts,
switch arm and knob. and binding posts
ara described III to-morrow's install
shouIn he wide enough so that it will
not drop between the contact points,
nut not so wide that it cannot be set
70 touch only a single contact. Having
iocated the hole Tor the switch-arm
oo't, the switch arm should be placed
II position and the knob rotated in such
manner that the end OF the contact
fsm will describe an arc upon which the
contact points are to be placed. The
noies for the contacts should next be
drilled, the spacing depending upon the
KIND OF contacts which are to be used.
The movable base l. is a square piece
o. dry wood 4 inches long, A inches
vide. and about 34 inch thick. Care
should be taken to have the edges OF
.nis block cut square with respect tc
the sides.
Now screw panel NJ to the movable
osse l., as shown in Fig. i. Care
shouid be taken to have the edges OF
me blocks Al and l. evenly lined up sc
nj 1nat the two edges of the block L
rig. !, which slide along the inside
cages Of the strips H and I will be
'"ootn, continuous surfaces.
t:-eH Or Primary Coil
Ire cardboard tubing for coil tube F
Is l. 47e inches i'll diameter by inches
..ong- About two ounces of No. "a Coz
40. Zo) double cotton-covered copper
nire IS used for winding the coil
E,onch two holes in the tube about one
hsi inch from one end. Weave the
~lre through these holes in such way
Ihat the end Of the wire will be firmly
anchored. leaving about twelve inches
OF the wire free for connecting. Start
with the remainder Of the wire to
WIND turns in q single layer about the
TUBE, tightly and closely together
Aiter one complete turn has been
wound on the tube hold it tight and
take off a tap. This tap i. made by
ewlsting 6-inch loop Of the wire to-
sether at such place that IL will be
slightly staggered from the first con-
nection. Proceed in this manner until