New-York tribune., 1922-05-21

=, NiS" PuHNleu IN tHe tobe as at
the start, leaving about twelve inches
of wire free for connecting. It is TO
De understood that each of the eighteen
taps Is slightly staggered to the right
from inc one just above so that the
taps will not be punched along one
Iine on the cardboard tube. See Fig. 2.
IT might be advisable after winding
the tuning coil to dip the tuner in hot
paraft'n. Glue cardboard cover to
the end of the tube where the single
turn taps are taken OF.
The Panel
Panel X should be made from board
! = inches long by Az inches wide and
about II inch thick. The position Of
the contacts can best be determined by
, inserting the switch arms in their re-
sectlve holes and turning the knobs so
that the ends of the switch arms will
describe arcs. The position of the sew
eral holes for the binding posts, switch
arms and switch contacts may first be
laid out and drilled.
The "antenna' and ground" binding
! posts may be ordinary 8-32 brass bolts
about lh2 inches long with three nuts
and two washers. The first nut binds
the bolt to the panel, the second nut
holds one of the short pieces of stiff
wire, while the third nut holds the
| antenna or ground wire as the case
may be. The switch arm with knob may
be purcha sed in the assembled form or
1t may be constructed from a ss-inch
slice cut from a broom handle and a
| bolt of sufficient length equipped with
tour nuts and two washers, together
with strip Of thin brass. The end Of
the switch arm should be wide enough
80 that it will not drop between the
contact points, but not so wide that
1T cannot be set to touch only single
contact The switch contacts may be
OF the regular type furnished for this
purpose, OR they may be 6-32 brass
bolts with one nut and one washer
each.
! The lxed base B is a piece Of dry
wood 5]2 inches wide, IL inches long
support } for the fixed coil tube is 5ia
inches wide (the width of the base), 6
incnes long and about !: inch thick
This board should be screwed TO one
end of the base so that it is held Sc
curely in vertical position. It will
then project about five inches above
the base G..
A strip OF wood !, II inches long,
SIG inch wide and about !. inch thick,
box nails or small brads so that It is
even with the rear edge, as shown in
figure /. The upright panel NJ having
been fastened to the movable base L,
rs previously explained, is placed in
position as shown. The next step is
TO locate the strip II in such position
that the block L will slide easily back
base B. Having found this position
this strip is secured in the same man
ner as the strip l. II is, of course,
understood that neither the movable
coil tube S nor the switch contacts and
! binding posts have, up to the present
time, been mounted on the upright
panel NJ. The wooden parts for the
loose coupler are now finished and
should be covered with parafin.
the coil tubes P and to dip them in
hot paraffin. This will help to exclude
moisture. Have the paraffin heated
until it just begins to smoke, so shat
when the coils are removed they Wlll
have 8 very thin coating Of paratiln.
Variable Condenser
The variable air condenser should
have a maximum capacity of between
o.OOO4 and O0O05 microfarads (400 to
500 micro o-microfarads). The type pic
tured in Fig. ] is inclosed in round
metal case. but the "unmounted" type
may also be used. The variable con
denser is mounted on board (R. Fig.
"a about 10 inches long. 5hs inches
vide and q inch thick. The strips of
wood are fastened under the ends so
that wires may be run underneath for
connections After the holes for the
detectcr binding post and also the holes
for the telephone binding posts y
have been drilled the board should be
coated with paraffin.
Crystal Detcctor
The galena crystal d may be mounted
as pictured in Figs. l and 2. The
holder for the crystal is metallic
pinch clip such as the ordinary battery
be bent into a convenient shape 50 that
it may be fastened to the base.
The wire X which makes contact with
the crystal is a piece OF fine wire
(about No. 800 which is wound into the
| form of spring and attached to q
! heavy piece of copper wire (abcut NO.
l4, This heavy wire is bent twice at
right angles, passes through the bind
ing post and has a wood knob or cork
fixed to its end as shown It is de-
sirable to have the fine wire OF springy
material, such as German silver, but
copper wire may be used if necessary.
! The Importance of securing tested
galena crystal cannot be emphasized
| too strongly, and it should be under
stood that good results cannot be OBJ
| tanned by using ali insensitive crystal.
! Assembling Coupler
The movable portion of the coupler
should be assembled first. AS shown
in Fig. i, the fittings making up this
part of the set are the movable base
L, the coil tube support NJ and the
coil tube S. Insert in NJ the six switch
contacts (machine screws), the switch
arm, and the binding posts, in the
proper holes, which have been drilled
Adjust the switch arm until it presses
| firmly on the contact points (both
heads) and fasten the bare end of 8
! No. "a copper wire between the nuts
| on the end Of the switch arm bolt 9
Iigs. l and 2, which projects through
The panel NJ. Wind this wire into the
form of a spiral of two or three turns
like a clock spring, leaving few inches
of the wire for connection. Insert two
small screws Y, Fig. /, in the panel
NJ, so that the switch arms will not
drop of the row Of contact points
when the knob is tnrned too far.
The coil tube S is now ready to be
| fastened in position on the panel NJ
| Cut a 1-inch hole in the cardboard
end Of the coil tube and place it with
the closed end next to the panel NJ in
Z.