White Bluffs spokesman. [volume] (White Bluffs, Wash.) 1907-1938, 1926-01-22
r ADI o

ACO oO l. OlCoC, l. oChOl VI AIdolO,
in advising amateur radio users on
set operation, reviewed the findings
of survey on the significance of low
internal resistance batteries prepared
by w. A.. Brannon, research engineer
for the Ray-O-Vac battery manufac-
turers. He emphasized the para
mount Importance of this feature as
essential to the obtaining of perfect
reception" DR.. de Forest said:
Call radio engineers are continually
striving to perfect audio application
in radio receivers to point where
audio frequencies can be heard in
their natural tone, without blasting"
or distortion. To this end numerous
improvements have been made in au
dio transformers and loud speakers,
many of which are extremely refined
and may correct only small part of
the distortion which occurs, for exam
pie, in a two-tube audio ampliier, yet
each improvement introduced adds to
the production cost of the radio re-
ceiyer.
"Many set manufacturers now see
the solution to this problem in the B
batteries AS long as two years ago
it was noted that some makes of B
batteries produced bowling and dis
tortion whereas other makes would
work the set without blasting" The
possibility that the B batteries were
contributing more to this studio dis
tortion than other factors which re-
quired expensive refnements in ap-
paratus for their correction, caused a
to undertake an extensive study of
the effect Of B battery resistance in
audio circuits.
"The results of this study showed
that when the internal resistance to
the B battery increased above GER
tain value in two-tube amplifier,
sufficient voltage drop occurred in
the detector B battery to cause mark
ed variations in the detector plate
circuit.
"The output of two-tube audio
amplifier after passing through the
loud speaker must return through the
common B battery which is usually
80 to 1876. This output current is a
pulsating direct current and when it
encounters the internal resistance of
the detector tube B battery it suffers
a resistance. drop. due to the pull
sating character of this audio circuit
current, the voltage produced in this
resistance drop is continually chang
ing and these changes are reflected
in the detector plate circuit, which is
coupled to the audio amplifier through
the first radio transformer. Through
this coupling the changes are ampli- |
fed through the amplifier tubes until |
they reach high values and at certain |
audio frequencies will produce tre-
mendous amplification and the we'll
known regenerative howl.
ut was also found by this investi-
eating laboratory that with most
radio-amplifiers this B battery distor-
ton would occur when the internal
resistance of the detector battery |
amounted to as little as Is ohms,
though 1t was also observed that diff
ferent audio frequencies were ampli-
fed more at certain B battery resist
ance than at others.
zone remedy for this type of audio
distortion is a separate detector
battery However, it is possible to
construct battery which will not
have a high internal resistance, In
which case no separate detector B
battery is necessary to avoid distor-
ton due to internal B battery resist
ance, provided no more than 221s |
volts of B battery is used on the de- |
tector tube. Many set makers, hav-
ing discovered the improvement in
amplification gained by the use of
these low resistance batteries are
now recommending their use with re-
ception sets in preference to high re-
sistance batteries"