For quite a range of wave-lengths we may use the same loading coil and tune the antenna circuit entirely by this series condenser. For some other range of wave-lengths we shall then need a different loading coil. In a well-designed set the wave-length ranges overlap. The calculation of the size of loading coil is quite easy but requires more arithmetic than I care to impose on you at present. I shall therefore merely give you illustrations based on the assumption that your antenna has a capacity of 0.0001 or of 0.0002 mf. and that the condensers which you have bought are 0.0005 and 0.001 for their maxima. In Table I there is given, for each of several values of the inductance of the primary coil, the shortest and the longest wave-lengths which you can expect to receive. The table is in two parts, the first for an antenna of capacity 0.0001 mf. and the second for one of 0.0002 mf. Yours will be somewhere between these two limits. The shortest wave-length depends upon the antenna and not upon the condenser which you use in series with it for tuning. It also depends upon how much inductance there is in the coil which you have in the antenna circuit. The table gives values of inductance in the first column, and of minimum wave-length in the second. The third column shows what is the greatest wave-length you may expect if you use a tuning condenser of 0.0005 mf.; and the fourth column the slightly large wave-length which is possible with the larger condenser. TABLE I Part 1. (For antenna of 0.0001 mf.) Inductance in Shortest wave-length Longest wave-length in meters mil-henries. in meters. with 0.0005 mf. with 0.001 mf. 0.10 103 169 179 0.20 146 238 253 0.40 207 337 358 0.85 300 490 515 1.80 400 700 760 2.00 420 750 800 4.00 600 1080 1130 5.00 660 1200 1260 10.00 900 1700 1790 30.00 1600 2900 3100 Part 2. (For antenna of 0.0002 mf.)