The Challis messenger. (Challis, Idaho) 1912-current, 1925-10-28
BY r. c. HITCHCOCK, in New Yor,
.ierald-Tribune.

BY r. C. HITCHCOCK, In New York
.ieraId-Tribune.
Inree-tube sets are very popular to-
day; three-tUbe set may be said to
occupy the middle position between in
expensive outfits, as, for instance, neu-
trodynes and superheterodynes- One
OF the reasons for the popularity of
the three-tube set Is its reasonable
cost, and another Is that most three
tube sets Will operate loud speaker
To do this the ordinary three-tube set
uses regenerative detector and two
audio ampli6ers- A more recent ten
dency, however, Is toward radio-fre-
quency amplifers- The primary cause
Tor this tendency is that there Is no
troublesome regeneratfve howl spread
throughout the nefghborhood Of the
receiving set, and a secondary cause Is
the theoretical knowledge that greater
distance Is possible with q radio than
with an audio stage of application
, To be perfectly fair, 1t must be adj
mitted that practical tests seem to
show that audfo amplifcation gives
greater volume on the nearer stations
but viii not bring In the far ones;
while on the other hand radio amplif-
cation gives consistent clearness and
distance The main difficulty with q
one-step radio-frequency amplIfer Is
TO get power enough to operate a loud
speaker with only two other tubes,
after hearing the distant station By
using a suitable audfo transformer IT
Is possible to get satisfactory loud
speaker volume on the nearer stations
with one stage of audio amplif1cation,
though II often seems to be rather
weak on other stations The greatest
advantage Is that much less noise VIII
come through 4 set which Is equipped
with radio ampltfer, and at the same
time the distance Is undeniabIy great
er- If clear reception Is wanted ut all
times, the loud speaker should be used
Tor the nearest stations, and phones
Tor distance; this is a good type of
.hree-tube set to build OF course, an
'ther tube may be added later. but the |
main part Of the set remains unal- |
cred The following description Il \
hat of the three-tube set This set,
hen, uses a radio amplifier for dis
ance, a regenerative detector for |
maximum volume from the detector,
md 4 six-to-One high-quaIity audio
for loud-speaker opera
ion
Eliminates intsrferenee.
Having the radio amplifier connected
o the antenna circuit eliminates the
troublesome local interference which
} associated with most regenerative
eceivers- A further improvement over
he single regenerative set Is noticed
, regard to the amount Of static re
eived when 4 radio amplifier is used
his may be explained by saying that
here are two separate tuned circuits;
rst the radio amplifier; and second,
he detector circuit Static. a more or ]
IS untuned ether disturbance, is
,rced to travel through two tuned /,
rcuits before being audible, and a
reat deal of It Is thereby filtered out.
.cause tuned circuits respond poorly
waves to which they are not tuned
Is distinctly noticeable that static
less bothersome with this set than !
18th 4 regular regenerative detector $
Regeneration Is used on nearly all
atoms but some local stations-come
with such volume that regeneration
not needed. and this control is then
erely left unused-or the regenera-
IN dial may be rotated backward 20 '
to oppose the field of the coil from o
hich 1t feeds, thereby making q n
tooth volume control for nearby pow 3
full stations lJ,
The set mounted on 4 board, which "
addition to being less expensive, 4
inmates the dielectric losses Of a a
IL camel and its inclosing cabinet n
ire timed copper wire Is used for s.
ring-the tin protects the wire from a
idation and corrosion which event Il
lily make poor connections Of bare II
pper wire As the wire Is bare 1t IL ..
insulated. and this reduces the d. b
.ctric losses which are always pres b
!, with covered wires The "A" bat
y leads, not carrying critical radio u
rents, are heavy undiscovered
snded wires tackled down to the
md out OF the way.
The individual panels on which the ps
ldensers and other instruments are oil
tened are L" sections cut from old re
rage-battery containers. These con- fr
ners are of hard rubber. and make CT
client panel material Cut them tn
h an old wood saw. the coarse teeth M
ke better>looking job than If a Gu
'kssw IS used In finishing. the Gu
es should be squared with file. gr
the sides snoothed with fine sand co
er. finally polishing with OIL LEI
he wiring diagram shows the three so
rs used liz parallel. so that they are tn
iron single six-ohm rheostat- tn
. set uses the regular fve-vo.t 20