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MARCH, 1926
AN ALL PURPOSE COIL WINDER
587
d
12
10
9:
8
7
6 5
4
1
n
io
l5^
20 :
2530
40
50
60
70
80 H 90 100
150
Index Line
Key
5 6
7 1 8
9 10
15
Y
CHART II
Connect three known values as per key, and read fourth at point of intersection.
Example: If L=170 mh., d=3," and n=196, then 1=3"
L
r20
30
40 Y 50 60
80 100
150
^200^ 250 300
400 500 600
800 1000
1500 2000
3000 4000
A 30
-40
50 h60
80 100
150 ; 200
300
400 500 '600^
800 1000
1500 2000
3000
4000
5000
.00001
-.00002
.00003
.00004 h .00005 .00006
.00008 .0001
.0002
.0003
.0004 .0005 .0006
.0008
F-.ooi
L.002
v "
CHART I
Connect two known values and read third at point of intersection.
Example: If A = 550 m. and C=.O005 mfd then L 170 mh
COIL DATA CHART
With the aid of this chart, a ruler, and pencil, the experimenter can very simply determine the approximate specifications for a solenoid coil to cover a definite frequency spectrum (wavelength range) with any condenser on hand. Full information for its use was contained in an article by Mr. Homer Davis, on page 46 of the May, 1925, issue of Radio Broadcast. Briefly, the chart is used in the following manner:
Suppose the constructor has a .0005-mfd. variable condenser and he wishes to cover a tuning range whose extremes are 545 kc. and 1 500 kc. (550 to 200 meters). Therefore, he must wind a coil so that, with the condenser plates entirely meshed, the tuned circuit, comprising coil and condenser, will respond to 545 kc. (550 meters). The problem is to first determine the inductance value in microhenries. By connecting together with a ruler and pencil the values of capacity (.0005 mfd.) on column C and the wavelength extreme (550 meters) on column \ (wavelength), and continuing this line so that it intersects column L, a value of L (inductance) is denoted.
Now, knowing the size of wire he is to use. the constructor looks for the number of turns to the inch for that particular size of wire as indicated on the wire table, Fig. 13, and then spots this position on column "n" above. If No. 18 d.c.c. is to be used, the number of turns per inch will be 19.6. Then he, knowing the diameter of the coil he is to wind, draws a line from the diameter figure point on column "d" to the inductance value in microhenries on column L, determined previously. This latter line between d and L intersects the index line. Now from the spotting on column n (19.6 if 18 d.c.c. be employed), a line is drawn to pass through the point of intersection on the index line continuing on to the column L, thereby indicating the approximate length in inches of the coil to be wound. Knowing this value, then L times n equals the number of turns for the complete coil.
THE ASSEMBLED WINDER Clamped to the bench and ready for work. By comparing this picture with the illustration Fig. 1, which shows the winder in operation, it will be plainly understood how the solenoid form — and other forms too for that matter — are: fixed to the winder
Radio Broadcast Photograph