The Ely miner. [volume] (Ely, Minn.) 1895-1986, 1925-10-23
BY z. c. HITCHCOCK, In New York
Herald Tribune.

BY z. c. HITCHCOCK, In New York
HeraId-Tribune.
Three-tube sets are very popular to-
day; three-tube set may be said 70
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 a regenerative detector and two
audio amplifiers. A more recent ten
oency, however, Is toward radio-fre-
quency amplifiers. The primary cause
for this tendency is that there is no
troublesome regenerative howl spread
throughout the neighborhood Of the
receiving set, and a secondary cause is
the theoretical knowledge that greater
distance Is possible with a radio than
with an audio stage Of amplification.
To be perfectly fair, it must be adj
mitted that practical tests seem to
show that audio amplification gives
greater volume on the nearer stations
but will not bring in the far ones
wnlie- on the other hand radio amplifi-
cation gives consistent clearness and
distance. The main difficulty with a
one-step radiO-frequency amplifier Is
TO get power enough to operate q loud
speaker with only two other tubes,
after hearing the distant station. By
using suitable audio transformer II
Is possible tc get satisfactory loud
speaker volume on the nearer stations
with one stage Of audio amplification,
though 1t often seems to be rather
weak on other stations. The greatest
advantage is that much less noise will
come through a set which is euuipped
with radio amplifer, and at the same
time the distance is undeniably great
er. If clear reception is wanted at all
times, the loud speaker should be used
for the nearest stations, and phones
for distance; this Is a good type of
three-tube set to build. Of course. an
other tube may be added later. but the
main part Of the set remains unal-
tered. The following description is
that Of the three-tube set. This set.
then, uses a radio amplifier for dis
lance. a regenerative detector for
maximum volume from the detector.
and six-to-one high-quality audio
transformer for lOud-speaker opera
ton.
Eliminates Interference.
Having the radio amplifier connected
to the antenna circuit eliminates the
troublesome local interference which
is associated with most regenerative
receivers. A further improvement over
the single regenerative set is noticed
in regard to the amount of static re-
ceiyed when radio amplifier is used
This may be explained by saying that
there are two separate tuned circuits;
first the radio amplifier; and second
the detector circuit Static, a more or
less untuned ether disturbance, is
forced to travel through two tuned
circuits before being audible, and a
great deal of it is thereby filtered out.
because tuned circuits respond poorly
" "oNSS W "hiSu tuSy are uOt tuned
1t is distinctly noticeable that static
is less bothersome with this set than
with regular regenerative detector.
Regeneration is used on nearly all
stations but some local stations come
in with such volume that regeneration
is not needed, and this control is then
merely left unused-or the regenera-
ton dial may be rotated backward so
as to oppose the field of the coil from
which it feeds, thereby making
smooth volume control for nearby DOW
erful stations.
The set mounted on a board, which
in addition to being less expensive.
eliminates the dielectric losses of
long panel and it's inclosing cabinet
Bare timed copper wire is used for
wiring-the tin protects the wire from
oxidation and corrosion which event
ually make poor connections of bare
copper wire AS the wire is bare it is
air insulated, and this reduces the d.
electric losses which are always pres
ent with covered wires. The "a" bat
terry leads, not carrying critical radio
currents, are heavy rubber-covered
stranded wires tackled down to the
board out of the way.
The individual panels on which the