The Washington times., 1924-05-08
GRID LEAK HAS
VITAL: ROLE
80
IN SET
1t Is More important Than
Safety Valve in Steam
Engine

The grid leak IL far more i'm.
portant an item in a radio set than
the safety valve is in a steam en-
CINE. 1t controls the flow Of cleo. |
irons in the circuit.
Elections carry music from the
antenna to your ears. Your an
tenna may be perfect and your
tubes may be operating at remark
able efficiency; but II the electrons
do not move along the path to your
ear in a smooth and orderly man.
ner, the music Is distorted.
Volume depends very much on
the grid current and directly ON
the plate current. An important
current is the number of negative
electrons which are attracted to the
grid from the filament. The mega
tive charges on the grid sometimes
reach a point where they practically |
stop the flow Of plate current. The
grid current piles them up. Unless
grid leak is in use the tube will
become choked up and will not
operate. If the grid leak is the
incorrect size the tube will only par
TALLY operate.
Makes Signals Stronger.
IuS CRU IeAk COtluSuScT pcEIluLS
incoming signals to enter your tube
without loss Of energy in the grid
leak; but the grid leak Is the true
controller Of the system. If the
| negative charges on the grid are
permitted to accumulate. they simply
clog the circuit. The grid potential
Is lowered and the plate current
10 lowered. The grid leak permits
ha 60 30
the plate current to its normal
value.
If you have never changed your
grid leak you will be surprised at
the different results you get from
different sizes. Local stations may
| come in best using two megohm
100000 ohms) leak; station 500
miles away may come in best using
IA megohms, while distance sta
tions may come best using 4
megohm. Best, means there may
be from 100 to 500 per cent differ.
ence in your volume.
Manufacturers Of sets usually sup.
ply megohm leaks with their sets.
The only reason for this is because
two Is an easy number to say and
to remember. The public has been
have been pleased 10 demonstrate to
several manufacturers that where
their formulas and designs come out
at 100000 ohms, the unknown
losses in other parts Of the design
and in different material used, may
change the figure.
Only Part Of Story.
This is only part Of the story.
Each type tube creates new condi-
tons. The L.. V. 1879 provides
higher emission at low filament tenn
peratures. The u. V. 201-A aver
ages five times the emission of the
ordinary simplifying tubes. The
emission or flow of electrons varies
with the current and voltage being
used. In other words. every time
you alter your rheostat or your 3D.
or "A" battery. you should vary
your grid leak.
Each type tube, each individual
tube OF same type, each variation
IN voltage, current or in strength
Of signal requires a variation in
Grid resistance for maximum eff
| cheney and that variation is COW
cred by radio engineers as follows:
w. u. d. II, 2 to 3 Megohms.
U. v. 200, II to 2 Megohms.
u. V. 201-A, 2 to 9 Megohms.
e. V. 1879, 2 to Megohms.
In the grid leak you are dealing
with minute electrons of electricity
passing over a path of extreme
high resistance 500. 10000 to 80, COO, 900
| ohms. Here is the essence for
great deal of research work The
problem of handling such minute
| portions Of electricity at such ex-
! traordinary high resistance re-
sembles somewhat the problems Of
dealing with lighting. s.
Two storm clouds are filled with
energy. The electricity generated
is enormous: the path between the
clouds, or from the clouds to the
earth, is possibly a mile of thin air.
Its resistance is beyond comprehen-
sion. Finally the pressure becomes
so. great the electricity jumps. II
| there was a copper wire or other
easy conducting path. there would
be no zigzag and no thunder. 1t
Is exactly the same in the receiving
| set.
Jump Along Leak.
The accumulated charges jump
along the grid leak. If the path
Is O. perfect conductor, there is no
noise. If the grid leak element is
uneven, or only partially a con-
ductor, then the grid leak actually
creates noises in your set.
There has been considerable propa-
ganda on grid leaks to the effect
that II your grid leak Is the incor-
rect resistance you can COMPENSATE
by adjustment of your variable con.
denser. This Is an absolutely in.
correct method of procedure. One
cannot adjust resistance by altering
capacity. If your grid leak is the
wrong size. you must get another.
If they are certified correct, then
you know what you are getting.
and can try out several sizes until
lou find the one best suited 70!
| ,,aur M iNI1IaY 1-anIirapannk