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A Winder for Small Inductances
74'
between 125 and 160. Double cotton covered wire varving in size from No. 24 to No. 28 may be satisfactorily used.
Plate circuit: — Connect two coils in series, using the same size wire as for the grid coils. As few turns as are necessary to make the tube oscillate uniformly over the entire range of the
FIG. 13
Another view of the cam and nozzle. Here, also,
is shown the method of obtaining tension on the
roller bearing, provision for binding and the counter
details
s. s. enamel wire. The second stage coil consists of 600 turns of the same wire and the third stage coil consists of 1000 turns of the same size wire.
Secondaries: — Connect two coils in series, each consisting of 1,000 turns of No. 36 s. s. enamel wire for each stage. The first stage coil is tuned by two .0005 mfd., micadons while the second and third stage coils are tuned by a .00025 mfd rnicadon, one for each stage.
Oscillator Coils, Grid Circuit: — Two coils are connected in series. The number of turns for these coils depends upon the size of the oscillator tuning condenser and usually varies
FIG. 14
A completed set of intermediate-frequency amplifier
coils mounted in position in an I. F. unit of a second
harmonic super-heterodyne receiver
oscillator condenser are used. This number varies between 50 and 75. The inside diameter of the coils is approximately f." The
overall dimensions of a single coil are -jV' x ,1"
I 2 •
It is important that the .00025 rnfd. condensers be matched. A small variable neutralizing condenser may be shunted across one of them and varied until the values of both are equal. This may be considered as one of the minor and semi-permanent adjustments of the receiver.
l.ST STAGE OF INT. FREQ. AMP
A CORRECTED CIRCUIT DIAGRAM OF THE SECOND HARMONIC "SUPER" Minor corrections have been made, particularly in that the by-pass condenser on the first audio-frequency primary is connected from the plate to the negative filament lead instead of as shown on page 44 of RADIO
BROADCAST for November, 1924