San Antonio light. [volume] (San Antonio, Tex.) 1911-1993, 1925-12-27
REGENERAT|VE
SETS NOT SOLE
OFFENDERS
Many Other Types Of Radio
Receivers May SqueaI,
Expert Declares.
By JACK BINNS

One OF the most important actions
Of the fourth annual radio conference
was the step taken ultimately to stop
the manufacture of all types of radio
receiving apparatus which cause in
reference through radiation. This ac-
ton came as a direct result of the fail
ure to check the growth of the offend
ing types through the fundamentally
Of voluntary committees.
The interference caused by radiating
receivers invariably manifests itself
in the form of a peculiar whistle,
which, some Of our early engineers
with sense of humor, promptly dub
bed "birdies."
Some idea of the damage which one
receiver of this type may cause is il
Illustrated in the experiments recently
conducted by Messrs. W. II. Hoffman,
Don Mix, and Philip Zurian at Mad
ison, Wis. In these experiments q
single wv 100 tube successfully COM
municated with New York. or--in 9TH
er words its effective range Of radia-
ton was 1000 miles. This tube, Of
course, was used in a set designed for
the sole purpose Of Transmission. but
it is a good indication of the destruc
tive possibilities of radiating re.
ceiver.
PUBLIC PALACES.
The experience Of the voluntary
committees, formed to eliminate inter
ference by educational methods, has
shown that the public generally hos
come to believe that only those sets,
frankly made under a regenerative IL
cense, cause radiation. Another fallacy
in the public mind is that a stage of
tuned radio frequency ahead Of a re-
generative detector will prevent radia-
ton, and further that tuned radio
frequency sets do not radiate.
In the latter respect it is interest
ing to note that decision by Federal
Judge Campbell in Brooklyn, recently
handed down after thorough examina-
ton and demonstration clearly states
that tuned radio frequency set equip
ped with means available to the OPP
orator for controlling regeneration
both below and above the oscillating
point or threshold of oscillation is re-
generative and therefore employs the
feed-back principle.
FEED BACK NECESSARY.
1t is a fundamental fact that the
feed-back of energy from the plate 10
the grid of vacuum tube is necessary
to the production of the oscillations
which cause radiation.
Eynarirnanf ehar., h. 49,. -
ceiver which has a completely neu-
tralized stage OF radio frequency ahead
OF an oscillating detector. radioation
Will emanate from the coils associated
with the detector tube, and cause in
reference in the immediate neighbor-
hoor.. unless the coils are completely
shielded and radiation prevented.
The feed back of energy. which is the
root of radiation, can be caused by elec-
tromagnetic or electrostatic coupling.
In Other words, either by coupled coils
or by condenser action in some part Of
the circuits, such as the internal ele-
ments of the vacuum tube, or the cir
cult wiring. Radiation can only be
prevented by the naturalization or sup
preston of these effects. The latter is
less efficient than the former,
MANY METHODS.
There are many different methods
of neutralizing electromagnetic effect.
There is the neutrodyne system, where
the coils are mounted at an angle or
shielded, the method of mounting in
three places. and finally the concen.
trated inducements as d coils or To
roids.
None Of these ia sufficient In it
self TO prevent radiation. The receiy-
er employing anyone of them must
also have means of neutralizing such
as for instance the neutrodyne, or the
Scott Taggart arrangement, or else
resistance for SURPRISING the effects
Of capacity coupling over the range Of