366 6.77 370
8.00 550 10.20 550

Part 2. (For core of 5.0 in. diam.)

2.00 120 2.22 160
3.00 158 2.93 215
4.00 194 3.58 265
5.00 228 4.22 310
8.00 324 6.00 450
10.00 384 7.10 530
12.00 450 8.30 625

The coil which you wound at the beginning of your experiment had only 75
turns and was tapped so that you could, by manipulating the two switches
of Fig. 112, get small variations in inductance. In Table III is given
the values of the inductance which is controlled by the switches of that
figure, the corresponding number of turns, and the wave-length to which
the antenna should then be tuned. I am giving this for two values of
antenna capacity, as I have done before. By the aid of these three
tables you should have small difficulty in taking care of matters of
tuning for all wave-lengths below about 3000 meters. If you want to get
longer waves than that you had better buy a few banked-wound coils.
These are coils in which the turns are wound over each other but in such
a way as to avoid in large part the "capacity effects" which usually
accompany such winding. You can try winding them for yourself but I
doubt if the experience has much value until you have gone farther in
the study of the mathematical theory of radio than this series of
letters will carry you.

TABLE III
Circuit of Fig. 112
Number Inductance in Wave length with antenna of
of turns. mil-henries. 0.0001 mf. 0.0002 mf.
14 0.04 120 170
20 0.07 160 220
28 0.12 210 290
36 0.18 250 360
44 0.25 300 420
56 0.38 370 520
75 0.60 460 650

In the secondary circuit there is only one capacity, that of the
variable condenser. If it has a range of values from about 0.00005 m