The Carbon County news. [volume] (Red Lodge, Mont.) 1924-1931, 1925-07-23

He has found that there is pleasure
in operating radio set even if he pays
no attention to what is coming in over
the ether. for it is then that he is
tempted to try little experiments that
help to unfold the whole mystery of
wireless communication.
This explains how Smith discovered
that he could not get any results from
the photograph horn when he substi-
tuted one of the earphones for the
loudspeaker unit and tried to make the
crystal set do the work of the tube
set.
That's funny" he said. when /
put the phones to my ears / can hear
our local station as though it were
right in this room. Now why isn't
this noise amplifed when | hold one
of the phones to the place where the
loudspeaker unit hooks on to the phon-
ograph?"
Because" I explained, Gin your
crystal set the only energy that causes
the variations in pulsations in the
phone circuit is that which comes in
over the aerial. In your tube set the
pulsations are enlarged-amplified--
by means of the B battery current"
"I'm glad you explained this" Smith
said, because thought there was
something the matter with the ear
phones and was about to take them
apart. / might have ruined them"
''That might have been a good in
vestment," | retorted. "You might
easily have learned something about
loudspeakers, since the earphone is the
basis Of all the devices you see for the
final reproduction of the received
sounds"
Smith was somewhat surprised to
learn that the difference between loud
speakers, as well as that between loud
speakers and earphones, was more
than one of size. He had no idea that
aside from variations in the size and
design of the horns there are three
broad classes of loudspeakers.
The first is the simplest type, be-
cause il is really an enlarged single
earphone. It is known as the electro
magnetic type and does just about
what its name implies. A thin iron
disc, known the the diaphram, floats
on the poles of the electromagnetic.
The magnet in the delicate radio phone
receiver, or simplified loudspeaker, is
usually referred to as solenoid, which
is the technical name for a wire spiral
through which current is passed. For
Smiths purpose it was only necessary
to picture this part Of the sound re-
producing equipment as horseshoe
shaped coil of fine wire wound around
an iron core. When current is passed
through the coil, or solenoid, the iron
cores attract the iron disc across their
ends in varying degrees.
In order to obtain more volume with
the same amount of current, second
general type Of loudspeaker has beer
developed. This is known as the cleo
tro-mechanical type, and is also JUS
about what its name implies. Electro
magnetic force is supplemented by me
chanical action.
In this type the poles of the solen
ODDS do not pull directly upo nthe meta
disc or diaphragm. The pull is upoi
and armature which, in turn, is con
nected with the diaphragm through
series of miniature levers. Smith coul'
clearly see how this gave a sort of me
chanical advantage, making it pos
sible to get lot of volume from yer
little energy.
Here returned to the earphones t
tell him that this mechanical typ
also is found in one of the popula
earphones, though the armature an
leverage action is necessarily minut
This gave me an opportunity to n
mind him that in buying phones 1t
important to buy the best, becau'
cheap ones are not only easily dan
aged but are frequently untuned. Thu
is, in pair Of good phones there
sufficient equalization between the tv
pieces so that the same tune com'
through each ear.
1.-THE third general type Of lou
speaker mechanism is a little mo
complicated ] added, "but it worl
on the electromagnetic principle.
is the electro-dynamic type where
the miniature coil that receives Il
pulsations from the plate circuit
the set floats in an air gap viii
becomes a strong magnetic field VIII
current flows through large windii
wire. For this type six-volt cure
supply for the large electromagnetic
necessary.
"0f course, there are mixed typ
And, finally, there is usually sol
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