New-York tribune., 1922-10-29
The Difference
I'm Radio and
Audio i'm Set
How Transformers Function
ON High Frequencies, and
Reason Audio Transform
ers Work ON ALI Waves
Have Different Ratios
Latest Design Has Separate
Transformers for Multi
Stage Radio Amplifying

| One of the most puxzling thing
about radio reception to the novice Il
tho function Of the radio and audi,
frequency transformers, PARTICULAR,
in view Of the fact that radio-fre
: quency amplidcation is something nsv
for short-wavs work.
As o result Of the large number o.
articles already written on the latter
the novice has, In general way, a fai,
understanding Of the fact that 1t i,
necessary to use different kinds Of
transformers for radio amplif1cation
on various wave lengths. Understand.
Ing this, he does not realize why this
Is not necessary In the case of audio-
frequency amplihcation.
Another puzzling point in connection
with transformers Is the question OF
ratio. He cannot understand why
ratio in radio transformer Is only
III, while that Of an audio transforner er
may range as high as i'll.
Hight Frequencies Involved
10 Is my object, In this article, TO
try TO clear up the doubts concerning
transformers and at the same time, as
far as possible, to explain their func-
tioning.
Radio-frequeney amplifcation on
long waves has been in successful op-
Grafton for few years now. and is due
20 the fact that the frequencies In
volved are not so high as those on
short waves. It is the problem Of very
high frequency that has made success
full amplihcatlon of radio signals SO
difficult on the broadcasting waves
These difficulties have now been prac-
tically overcome by the development
Of suitable transformers.
The radio transformer Is, TO all in
tents and purposes, purely tuned cir
cult of fixed value. It relies chiefly
upon the amplification characteristics
of the vacuum tube In Its operation
the transformer, passing along the out
put from one tube to the input Of the
other. 1t Is because of the fact that
these transformers are really tuned
circuits that It is impossible, at the
present time anyway to increase the
ratio moro than IL and still retain
efficiency.
Difficulty Overcome
Another great problem In radlo-fre-
quency Is the fact that in many cases
single stage Of radio frequency am
plification will work cxcellently, but
the. moment additional stages are in
cluded in the receiver the final results
are worse than with only one stage.
This. difficulty has practically been
overcome by some Of the designers of
radio-frequency amplifcation trans
formers by turning out second and
third stage transformers Of slightly
different characteristics from the first
transformer.
The value Of the radio transformer
is In the fact that it amplifies weak
currents. received on the aerial and
builds them up so that the detector
can get in its work. In building up
these currents 1t, Of course, also builds
up everything that is carried alonV
with the current. The reason that
this type Of transformer will only op-
crate on very narrow band of wave
lengths Is because of the terrific fire.
quencies that are involved in a very
slight change of wave length.
This can be clearly understood
when 1t is pointed out that the fre~
quency Of 300-meter wave is ! 1000 600
cycles per second, and that Of 360-
meter wave is $4,000 cycles a second.
while that Of 400-meter wave is 75O.-
900 cycles second. In other words.
with difference Of only forty meters
IN wave length there Is a difference ST
$4,000 cycles per second In frequency.
Compare this with the difference on
wave lengths Of 1000 meters, where tho
frequency Is $4,000 cycles O second,
and 5000 meters, where the frequency
Is 10000 cycles. In this case, It wifi
be seen that although there is a differ
ence OF 1000 meters in wave length
there IL only difference ~ fs9on
cycles in frequency.
Vibrations That Can BE Heard
The most difficult thing for the
novice to grasp is that the audio- fro
quency transformer will operats IN a
set irrespective of what wave length
is used. AS in the case Of the radio
transformer, the whole thing depends
upon. the frequency involved. The term
audio-frequency" means the range of
Vibrations which are audible to the
human. ear. The freauencies range
from sixty second up to 10000 a sec
ond, depending upon the acuteness Of
hearing of the individual. The audio-
frequency transformer is DESIGNED 70
cover this range OF frequencies, which
is not very difficult task when we
consider that the short wave radio.
frequency transformer must cover q
range OF frequencies varying 500, 900
cycles between the minimum and +ha
maximum limits.
The reason that the higher freuuen-
cics are. not involved in the audio.
transformer is because the detector
tube has rectified the received currents
before these particular transformers
come iEto operation, and the only cur
rens that they deal with is pulsating