Worcester Democrat and the ledger-enterprise. (Pocomoke City, Md.) 1921-1953, 1926-12-25

curse, on the characteristics of the
particular tube. From one and one
half to three volts usually will make
the tube function properly. To include
'C'' battery at this point. remove the
cad XXI, as shown in Fig. l.
The set Is easy to tune, as there are
only two major controls, antenna dial
and wave-length dial. After the de-
tector tube Is properly adjusted the
letting Of the rheostat can remain per-
manent and the volume Of the output
signal controlled entirely by the r. r.
tube rheostat. If the coils are prop
orly balanced the dials should read
alike and then can be successfully
logged. When tuning the set the dials
should be rotated slowly. a degree at
time, as the stations simply drift
In and out without the usual whine or
whistle. II the regenerative unit Is
correct, over-regeneration Is indicated
by signal becoming mushy when too
much capacity Is used-that Is. when
the dial Is advanced too far. II the
set has tendency to ''plop," remove
two or more turns from the secondary
side of the regenerative coil as q
means Of correcting the fault. An
other method Is to move the regenera.
tive coil from one-quarter inch to
three-eighths inch away from the Sec
ondary coil.
The value Of the "C'' battery used In
the audio circuit may he anything
from four and half volts to nine
volts or more II ninety or more volts
Of "B" battery are used. Most audio
amplihers work better with "C' bat
terry. and the saving of "B" battery
Is considerable in the long run.
Wave-Length Range.
The set should ordinarily tune from
200 to 526 meters smoothly and with
equal volume. However. the author
found one set In several he built that
was for some reason or other a little
tricky on wave lengths under 300 me-
ters-that Is, It had a tendency to
spill over and was difficult to balance.
This tendency was corrected by MAX
ing use OF the Rice system Of neutral
ization. This consists Of an Undue
lance and neutralizing condenser.
These parts are indicated In the draw.
ing to show their location, but need
only he used II difficulty Is experienced
on the low wave lengths. There Is.
however, only one chance in a hun.
dred Of their being required. The coil
is composed Of the same number Of
turns as the r. F. coil and is wound
directly over the r. F. coil.
The tube in the, last stage can be a
COLA If the horn type Of loud speaker
Is used. However, II the builder in
tends to use cone-type speaker. he
will require greater output voltage
properly to vibrate the cone. The use
Of a UX171 power is suggested here as
suitable means Of providing the nee
essary power without dlstorting the
signal. An anperite or similar fla
ment control device Of one-half am
pere capacity must be provided for
this type Of tube.
The choke and large condenser
shown In the diagram can be used or
not as the builder sees At. With their
use the output signal will be much
smoother, as the heavy direct current
is by-passed through the choke in.
stead Of being allowed to pass through
the speaker coil.
Parts Required.
The following Is a list Of parts &C
tually used, but there Is no reason
why the set would not work we'll II
other equally suitable parts Of good
quality were substituted:
One cabinet, 81 inches long and II
inches deep.
One Dashboard, by 2O-inch wood.
Brass strip, n by 1-16. See text.
One Radon panel, by 3-16 inches.
Two varia Jle condensers, COOS, Gen.
eral Instrument.
One variable condenser, .0002, Cen
eral Instrument.
Five 201-A tubes.
Two rheostats.
Two Radon sockets.
Three sockets, gang, bakelite.
Two tubular forms, 8 by @ inches
ana by thchea ttAui0n nara runber,
One grid leak, variable,
One grid condenser, y000ea,
Three amperiteS and MoOntings,
IA "
One audio transformer.
Two reelsto couplers.
Four reslstances, ,0s, %, 4 and 90.
Two coupling condensers, .OO6.
Twelve binding posts.
Terminal strip. IN by by 3-16
inches.
Terminal strip. ~ by 8 by 3.16
inches.
Three dialS.
One filament switch.
One pound No. % D. G. G.
One-eighth pound No. 80 d. G. G.
Necessary screws, wire for connec.
tons, etc.