The Ely miner. [volume] (Ely, Minn.) 1895-1986, 1926-01-15


Using Crys
BY LEWIS WINNER, in Radio World.
A very simple three-tube set using
crystal as a detector Is shown in
the illustration. The receiver employs
one step Of tuned RI with regenera-
ton, a crystal detector and two steps
of transformer coupled audio-fre-
quency application.
On most receivers, no matter how
many stages Of tuned RI you add, the
signals Of the local stations do not in
crease much. This was found to be
true on many tests with such receiv-
ers. The RF steps were so arranged
that they could be snapped in and out
of the circuit. station was tuned in.
The RI tubes were put in and then
out of the circuit. The difference was
so small that only with milliameter in
the output circuit could the effect be
noticed.
There are only about a dozen leads
to make. No soldering is necessary.
The Orbit toroid coils were used in
the set; also air-gap sockets.
List of Parts.
Two tuned radio-frequency trans
formers (toroids) L1L2, L4L5.
One variometer, L3.
One crystal detector, CD (carborun-
dunn.
Two audio-frequency transformers,
Att, AFT2 (Acme).
One y -ampere ballast resistors, RI.
Three sockets (air-gap).
Two .0005 mid. vernier variable con-
densers, with dials, C1C2 CO. S. Toou /.
One single circuit jack or two phone
tips, il.
One 312-inch dial (for variometer).
One A battery switch.
One Z by 21-inch panel.
One cable cord.
One Dashboard, by 10 by h.
Accessories: Bus bar, mounting for
crystal detector, batteries, phones, an
tenna, ground and lead-in wire, etc.
The shaft Of the variable condenser,
CT, that shunts the secondary of the
antenna coupler, LIZ, passes through
hole 316 inch in diameter, which is
6A inches from the left-hand edge of
and the bottom. Lay the, template
over this hole and then drill the hold
ing holes according to those laid out
upon the template The same policy
is followed with the other variable
condenser. The hole through which
the shaft of the variOmeter L3 passes
is 10A inches from both the right
and the left-hand edges 1t is also 80
inches from the top and the bottom of
the panel. The hole for the shaft of
the last variable condenser is 81
inches from the right-hand edge and
3k inches from the top and the bot
tom of the panel. The hole for the
filament control switch, S, is 10A
inches from the right and the left
hand edges Of the panel. 1t Is u inch
from the bottom of the panel This
necessitates cutting away small bit
of the Dashboard The holes for the
screws, which hold the Dashboard, are
best located by the builder, as these
depend upon the thickness of the base
board ETC. / used a comparatively
thin board and therefore had to place
the screws very near the bottom of
the panel.
We have now automatically placed
the variable condensers, variometer,
hon rd fob La
used to mount the coils onto the con-
densers. These condensers have spe-
cial provisions for mounting the coils,
which are placed at right angles To
each other. The set of plates of one
variable condenser runs In the OppO-
site direction to the other set of
plates That Is, one condenser is
mounted upside down. This was done
so that the coils could conveniently be
mounted. IF the condensers are
mounted in the regular fashion 1t will
be difficult to mount the coils
The transformers are mounted Mt
right angles to each other. The crys-
tai detector. which is Of the fixed type.
has a special type of mounting. You
cannot fit 1t into grid leak holder.
as 1t Is too small. Therefore take n
pair of mountings and bolt them to-
gether, seeing when. doing SO. that
the crystal fits into the holders. You
then have perfect holder. This ls
then screwed down 10 the Dashboard
and the crystal is fitted into the clips.
There was no jack used when this