Evening star. [volume] (Washington, D.C.) 1854-1972, 1926-02-10
FIFTEEN MINUTES OF
RADIO EACH DAY
BY JOSEPH CALCATERRA.
All Rights Reserved Repro. Prohibited
Rectifiers and Battery Eliminators.
Part ILL.,

The original application of the two
electrode tube as a rectitier or one
way conductor of current has been
used to advantage in battery chargers
using this element. Most fans know
that the old-type Fleming valve con.
sisted of two electrodes in a vacuum
tube. The cold electrode was simply
a metal plate. while the hot eIectrode
was a filament heated by passing
current through 1t. Under such CON
ditions current could be made to flow
In one direction, but not in the other
direction when a battery or other
source of current was connected be-
tween the fIlament and plate electrCde.
If an alternating current source Is
connected between the two electrodes.
one-half of the wave will be allowed
10 flow in one direction. but when
the direction of current flow in the
circuit is reversed. the current will
not flow through the tube. The tube
generally used for such rectifying
purposes is especially designed for
such use and contains only two ele-
ments. The ordinary type of three
electrode tube can be used as a rec
tifier by disregarding the grid cleo
trode and using only the filament
and plate electrode. The grid in that
case can be left out Of the current
entirely. or it may be connected with
the plate to be used as part of the
plate electrode.
Use Care in Connecting Terminal.
This type of rectifier allows cur
rent to flow in only one direction.
1t Is not -polariZing as is the
case with the vibrator type, so that
care must be taken to connect the
terminals Of the charger to tho prop
Inc Js, 20
the battery. These leads are usually
marked either with a plus and minus
sign or with a red marking to indi-
cate the positive terminal. In con-
Meeting the battery with the charger,
the positive (red) terminal Of the
charger should be connected with the
positive terminal Of the battery, while
the negative (plain or black lead of
the charger should be connected with
the negative terminal of the battery.
The electrolytic rectifier, especially
in its improved form as used in the
Balkite, has found a very wide appli-
cation in radio. It is the quietest in
operation and can even be used to
charge the battery while the set is
being used. The only attention re.
quired is to replace the water that
evaporates when it is in use. Since
distilled water is used to make the
replacement. the same as with the
storage battery, this item is not an
Inconvenience. There is practically
nothing to get out of order.
Rectifier Improvement.
Electrolytic cells can be connected
for both half-wave and full-wave rec
Ftification.
The mercury vapor rectifer has
not found any wide application in bat.
terry charging devices for radio use
because it requires attention in get
ting It into operation and whenever
there is any interruption in the serv-
ice line. It is used to great extent,
however. in large commercial install
lations and in power plants.
The latest device to join the ranks
of rectifiers adaptable for radio use
| is the Raytheon tube rectifier. The
details of operation of this device will
be described in tomoIrow's article.