Belt Valley times. [volume] (Armington, Mont.) 1894-1977, 1922-06-29

grid, determine the value of f.. Il Is
the negative potential which must be
applied to the grid In order to reduce
the plate current to zero. The value
ofhIEhiehH tsthe positive grid poten-
tiai that will cause the maximum or
saturatiOn current TO flow In the plate
circuit. is also determined by the rela-
tive position of the grid with respect
TO the hlament and plate. II the grid
Is Of very fine mesh, the value Of E
Is small because the electrons In pass
ing through the small mesh of the
grid on their journey from the fla
ment 10 the plate will negatively
charge the grid and will be repealed.
Similarly a small positive charge ap-
piled to a fine mesh will enc TO ac-
celerate the velocity of the electrons.
In case OF a very coarse mesh grid.
the electrons can pass through the ap-
ertures In the grid without coming In
30 close to the charge ON II and a
relatively high potential will be re-
quired on the grid to control the cleo
tron stream. or In other words, the
current flowing In the plate circuit.
Referring TO Fig. VIII, O-G. Is the
current that will flow In the plate cir
cuif when there is nc potential ap-l
piled TO the grid. Suppose a positive
potential as OIL is applied eathe grid
The corresponding plate circuit current
viii be I'D or BID, more than II was
shen the grid had no potential ap-
liied to IL.
A negative potential OF OH n now
TO the grid where OH il squal
q value to OIL, but opposite In sign.
application OF the negative po-
entfai when applied TO the grid will
the plate current 10 be reduced
0 a value H.C or A-C, less than 1t
vas when there was no potential APP
lied TO the grid. So It Is seen that n
egative potential when applied 10 the
rid does not reduce the plate circuit
urrent as much as the same positive
otential Increased the IJate circuit
urrent. This Irregular com1uctlvity Of
ne tube Is made use of when the tube
used as a detector or rectiner OF
ado signals.
The incoming radio signal Is q high
equency. alternating cnrrent-Let us
an alternating difference OF po-
initial whose maximum positive val :
is equal to OIL and whose maximum !.
.gatlye valne r. equal TO OH, to the :
I'd Of the three-eIectrode tube :
hose Characteristic curve Is the same ,
that shown in Fig. VIII. In Fig. !.
is shown the alternating difference !,
potential applied TO the grid. :
the first quarter of a cycle,
pm zero AT J to "A maximum mega :;
e value at X, equal to OH. the
ate circuit current Will vary from
9. Its value at T. when no grid DO
lfial is applied to a value at q equal
He
During the next quarter OF a cycle
2 grid potential changes from a
'ximum negative value az X TO zero
1.-The corresponding values OF
tie circuit current are shown by the
rtion OF the plate current curve .
I.
'uF1ng the next or third quarter
q cycle the applied grid potential
reases from zero at L to q maxi
m positive value at-M-equaEtaIL
and causes the plate circuit to In
ase from lib, Its value when the
potential is zero, TO I'D, an In
ase In plate current equal TO BID.
'uring the refnsinfng fourth quar-
OF a cycle az the applied grid poll
tiai varies from a maximum posi-
value at NJ TO zero at N, the plate
uft current varies from a value y
I.
Stunning that the Characteristic
re - shown In Pig. VIII and Zig.
with q potential Of 40 volts
ne plate. then, If the plate current
0 be reduced to ZERO by a varfa-
OF plate volfage-witb no pofen-
applied 10 the grid-the piateA
age must be reduced TO zero or q
Of 20 volts must be made. a