Evening star., 1924-11-02
FIFTEEN MINUTES OF RADIO EACH DAY
BY JOSEPH CALCATERRA.
Radio Editor of Popular Science MonthIy
All Fights RsssEvsd. Reproduction Prohibited.

The first important consideration is
that Of what types OF batteries to
buy.
The best batteries from tho stand
point of service and economy are
the larger batteries. Besides giving
greater value, dollar for dollar, the
larger batteries give more uniform
service for much longer time, and
thereby decrease tho amount of at
tention required by this item.
This means that If this point is
taken care of you can forget your
| maintenance item for d longer time.
The specific gravity of the storage
battery should never be allowed to
drop below 1,200. While this is not
the totally discharged point, best re-
suits cannot be expected il the bat
terry is allowed to discharge below
this point.
When dry cells are used as A bat
teries for tubes Of the WD-11, WD-12,
UC-199 and C-299 types, these should
be tested frequently to determine
their condition. The usual test used
is the ammeter test but this test
is not the most reliable for such
batteries.
The dete erninins factor which gov
erns whether or not the battery, can
De continued IN use is the voltage Of
the battery.
For WD-l,. WD-12. Gil and C-12
tubes a single 1h volt dry cell or
volt dry cells connected in
parallel are used. The voltage of
a new cell should register about )
volts. When the voltage of the cell
drops to below II volts the cell can
not be used efficiently for radio, al
though 1t may be used for bellringing
and other such uses around the house
The 41e volt units obtained by con-
Meeting three dry cells in series for
use with UV-199 and C-299 tubes are
not fit for use when the voltage drops
below volts, although the efficiency
Is lowered to some extent lust as
soon as they reach a point below 81
volts.
These tests should be made by a
voltmeter of the type shown in Fig.
2, whose whole range is up to volts
or less. II the other types which read
up to 80 or so volts are used the
graduation for such small voltages
as l." and are so small that the
readings are not reliable for frac-
tions of a volt
The same voltmeter can be used
to test the 4h-volt c battery The c
battery will last for a very long time
practically the shelf-life of the bat
terry 1t need not be discarded until
the voltage drops to about volts
B batteries should be tested with a
voltmeter similar in type to that
shown in Fig. 2, but with a range up
to 35 or so volts.
A 35-volt voItmeter can be used to
test 45-volt batteries by testing each
22E volt unit of the battery sepa-
rately.
; When the voltage of 22L-voIt B
, battery unit drops below 10 to il.
the battery should be discarded
When the voltage of a 45-volt unit
! drops below about so volts il should
be discarded.
Some fans have the idea that three
run down batteries reading Is volts
each, connected in series so that the
reading becomes As volts, will give
Just as good results as a new 45-yolt
battery.
Such. however. is not the case
When battery is run down to that
extent. the internal action causes an
irregular flow which results in noises
in the phones similar to the crack
ling of static.
When your batteries run down IN
that extent ii is good practice to
throw them away and buy fresh ones