Every evening, Wilmington daily commercial., 1922-04-22
RECEIVERS
ON RADIO APPARATUS
They Are an important Factor
to be Considered In Setting
Up Apparatus.

Telephone receivers pertaining to
radio, is another important factor to
be considered In setting up n radio
apparatus. A type OF telephone re-
ceiver which Ia finding much favor
and which can be coupled to some
form OF horn to make n loud speaker.
has mica diaphragm. Tho actuat-
ing element is a thin plato suspended
between the fat faces forming the
two poles of n permanent magnet and
on which there are two coils OF wire
wound round In tho usual fashion.
The thin plato II connected with n
small wire to tho mica diaphragm ut
It's center and operates IL In n manner
very similar TO the diaphragm In n
graphophone. A large sized receive-
Of this type, connected TO horn, pre-
ferably OF non-metallic material.
makes very loud speaker. A fibre
megaphone works very successfully
with such n receiver.
The best known loud speaker Ia com
posed OF metallic horn connected to
what is actually a telephone receiver
Of large size. The permanent magne,
Is energi1ed by al external source OF
Icurrent and tho diaphragm Is actual
cd by a coil of wire suspended between
tho pole pieces OF tho electro magnet
The actuatng current passes through
the sus pended coil.
An important element Of the re-
ceiving set is the ono which makes
audible the pulsating electrical cur.
rent, after II has been rectified and
amplif'ed. The sound originates, ir
all OF the present types OF Instruments
from n diaphragm which is made C
vibrate by the action of the current
Tho diaphragm may he OF iron. mica
carbon, etc. In all cases tho current
In the set. by electromagnetic action
actuates the diaphragm.
The simplest type In very similar
to the ordinary line telephone receiv.
or. There is n thin iron diaphragm
enamelled to prevent corrosion, which
is separated by a few thousandths o
an inch from the poles of n permanpn
magnet on which there are bohbinl
wound with very fine wire. Tn,
amount OF energy OF any electric mag
net depends on the ampere turns II
turn of wire with rs amperes woul,
have the same effect as rs turns witt
ono ampere of current. The ordinar,
line telephone receiver, dealing with
relatively large amount Of current. 4
wound with few turns OF coars
wire. The radio receivers. however
are actuated by very small amour
lof current. and their effectiveness 1
due to the great number OF turns
Fine wire is used 10 reduce the bull
of the receiver, and 10 keep the wir
near the core. where Il Is more effect
i've. The high resistance OF the wind
Ing has nothing to do with its effect
iveness, but It is an indication of th
lamount Of wire used. The wire /
wound over permanent magnet be
cause in that case the magnetic condi
tions are very critical. A slight chans
in ampere turns has its maximum in
huence on the diaphragm. For rad,
work. TO reduce the bulk. the perma
lnent magnet 10 mnde circular or hors
shoe in shape. II is said that the typ
of receiver with a complete circle c
steel as the magnet is moro effect
i've than the other type. IN which th
magnet has n gap. But il is difficu
10 find the difference between the tu
types. The amateur Is safe in buyin
any Of the well-known makes OF tele
phone receivers