Palisadian., 1925-10-09


The neutralizing condenser N. Thus
| each OF these two coils Is wound with
primary first, then secondary, the tap
point being made Is turns from the
end of the primary. There are three
coils to be wound, namely, the aerial
X. +. transformer and the two inter
stage transformers.
The. variable condensers that tune
the secondaries are O005 mid. repre-
sented In the diagram by CT, C2 and
C5. Thus the set has three controls.
II only two controls are desired. a
.OoI double condenser. where each half
Is .Uoo5 mfd.. may be used, the COM
mon rotor connecting to A minus and
the two stators connecting respectively
10 the grid of the second R. +. tube
tsecond from left), and the coil side
OF the grid condenser, CA. which Is
.oOO25 mid. 1t will be noted that this
rorces an apparent negative grid re-
turn in the detector stage, since there
can be but one grid return at the ends
or the two secOndaries. In fact, how
ever, the grid return Is slightly posi-
tive In the detector stage, due to the
manner of connecting the two-megohm
grid leak, R3 (grid post of detector
tube socket to A minus).
Ii .OOOsso mid. variable condensers
are to be used the coils would be made
as prescribed, except that the second
aries would have 81 turns of wire, in
stead of 45. In this case the tap would
be at the twentieth turn.
The tap is made nearer what n
known as the grid end.
Proper Connection Of Coils.
The aerial Il. F. T. Is connected
with the aerial Joined to the begin
ming. |. e., top of the primary winding.
when the form Is so placed that the
primary Is above the secondary. The
end of the primary goes to ground.
Now connect the beginning of the Sec
ondary, not to the fixed plates Of CT
and to grid, but to the negative A and
the rotor plates of CT. Numerically
as per diagram, connect 1 to aerial.
2 to ground, 8 to minus A and to
grid. This Is the inverse method Of
connection, the orthodox observance
Of polarities. With the rest Of the
II. F. wiring, however, this system Is
not followed. The first interstage cou-
pier (neutroformer) shown to the right
Of the first tube, Is connected with
the primary beginning ID Joined to
plate, the end Of the primary (2) going
to plus amplifier voltage. Here the
beginning of the secondary (3), which
adjoins the end of the primary, con-
meets the grid (instead of, as In the
previous case, to low potentially, and
the end of the secondary to negative
A. Thus the top, which Is Is turns
from the beginning of the secondary,
Is nearer the terminal thereof (3)
which connects to grid. The method
just described Is one wherein the pri-
mary connections are reversed, that
Is, the polarities oppose at the adjoin-
ing points e and 81. In neutrodyne
construction this Is correct
The second intersrage coupler Is con-
nected in the same manner as the pre-
ceding one (that is, unlike the aerial
coupler), except that (3) goes to one
side of the grid condenser, instead of
conductively to grid. The other side
of the grid condenser Is Joined to the
grid post of the detector tube socket.
Four bypass condensers are used,
two of .OO1 mid. each. across the Sec
Ondaries of the audio transformers,
and two of .0O2 mid. from the end (B
plus amplifier lead) of the two inter-
stage coupling primaries to negative
A, to bypass the r. F. current around
the batteries.
A separate rheostat, RI, actuates
the detectOr tube and Is of 20 ohms
resistance for the six-volt storage-bat-
tery-operated tubes. RI controls the
two amplifier tubes and is Is ohms.
A battery switch, S, may be used to
turn the set ON and off as a unit.
The coils should be mounted at a
57.3 degree angle. The neutralizing
condensers should be adjusted until
there is no squealing.