Belt Valley times. [volume] (Armington, Mont.) 1894-1977, 1925-10-08

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No. 40 enameled wire wound on .
wooden dowel one inch In diameter
The coupling condenser ca may be
one OF .001 mlcrofarad capacity. This
resistance 4 should not DO greater
than one megohm. A half megohzn
should prove suficient. The bypass
condenser ca should be one Of large
capacity. Il ID used mainly for the
purpose Of bringing the rotor plates
OF condenser CS as nearly to ground
potential as possible. and thereby re-
ducing hand capacity efFecta Amy
value between COS microfarad and
microfarad may be used.
The crystal detector Or ia one OF
the new type carborundum crystals
These ara sensitive and rugged and
viii stand up under heavy loads. They
are also OF the axed type, so that the
cat whisker nuisance Is eliminated
simplicity Of Operation.
Simplicity Of operation was one OF
the main considerations IN building
the set. Thus there are only two main
tuning controls In II. the two tuning
condenaera Then there Is the ticker
control for varying the sensitivlty OF
the circuit. The lnductlve switch
and the taps on the second tuning coil
are not brought out on the panel. A
short. aexibls lead running from the
crystal terminates In a small connectoE
clip. which may be connected to any
one Of the taps located on the tuning
coil. AS q means OF simplifying the
iilament circuits, salf-regulating rheo-
stats (A1 are used throughout IA place
OF adjustable rheostats. This is feas.
lble. since ali the tubes operate as
anpllners One rheostaf. however, is
used IN the fslament circuit Of the erst
tube. and this Is for the purpose Of
securing an additional volume contro'.
This rheostat should be one OF from
ak to ten ohms. either OF which gives
sufficient control OF the output Of the
fint tuha-
Also, for the sake Of simplicity.
jacks have been eliminated. There
are only four binding posts on the
panel two, A and @. for the lnput. and
two. 4, for the output The latter two
serve for the customary Jacks Az q
means for throwing the loud speaker
from the last to the preceding tube.
in case the volume warrants such
change, the switch IS has been pro-
vided. This automatically controls |
the fiIament circuit Of the last tube. |
so that 1t Is only lighted when the |
loud speaker IL In the output circuit
OF that tube. The switch is of the
type which closes two and opens one
contact. 81 Is the filament switch for
turning on and of the current II
should have the same external appear
ance as 50. The three battery bind
ing posts should be placed at the rear
Of the cabinet. The two binding posts
provided for the @ battery may be
placed IN the most convenient position
in the set
This set has not been tried with airy
cell tubes, but no doubt It will work
with these as long az the volume IL
kept down to moderate intensity.
Since the first tube ia operated as
voltage amplIfer by virtue Of the Inn
pedance coupling. better results should
be obtained II a high MI tube Ia used
in this stage. II. however. high MI
tube IL used. II is Of great importance
that the impedance OF Ia be high. be-
cauee a tube Of this type has a plate
FesIstancs in the neighborhood Of
5000 CHINA and II the Impedancs OF
IL is much less than this no advan-
tags is gained by the high MU.
List o. Parts.
One radio-frequency tuning coll with
Two windtngs One radlo-freQuency
tuning coli with one winding and taps.
One ticker coil, as described. One
choke coil, FIVE milf
henfies or greater. Two audio-fre-
1uency transformers. Two tuning con.
lensers. zoos MID -Four automatic
hIamenf reslstaneea One SIX or ten
,hm rheostat One coupling con
ienesr, lO01 MID. One bypass con-
ienser COS mid or greater One
yrid leak. 5 to megohm. One crys-
al defect0r. nxed caFborundunl. -Four
standard sockets and four tubes. One
ilament switch. One double pole.
IoubIe throw Jack switch. Nine bind
ng posts Two condenser dIaIs and 4
ne fickler knob. One panel. Xxi
inches. and one DASHBOARD. 7x20 inches. :
)ne cabinet TO match.
Since the tubes In this cabinet are
II working as ampIIners, all the grid
eturn leads should be connected to
he negative G battery terminal. md
be @ battery should be given a yalue
consistent with the plate voltage EN-
logged. The plate voltage should pref
rabIy be 07.8 or more. An the tubes
re more efficient when high plate
0lEages are used. and This Is particu-
49, $3.50 - 49, Ara4