High Frequency Apparatus Page 36

36 36 HIGH FREQUENCY APPARATUS condenser will have a capacity of approximately .001. mfd. These plates may conveniently be grouped up into units of ten plates each, each unit therefore having a capacity of .01 mfd. By assembling any desired number of units into a suitable case or rack, the correct capacity for the apparatus under construction will easily be provided. The tinfoil plates may be secured to the glass by means of quick-drying gold size, which is a varnish, or the foil may be applied after the glass has been given a very thin coat of beeswax applied when the glass has been heated gently over a flame or in an oven. In either event, it is well to apply the foil in a slightly larger size and trim afterwards. As the foil comes in sheets 6½ x 8½ in. this is easily done. When the foil has been secured on both sides of each piece of glass, the units may be assembled with strips of thin copper ribbon placed alternately projecting to right and left between the plates of the unit. These lugs, of course, provide the means of connection. The unit is then bound with linotape at top and bottom, the lugs folded around lengths of flexible lamp cord and soldered, and the entire unit immersed for two hours in a molten compound of equal parts of beeswax and rosin. When this mixture cools, it will form a solid, non-hygroscopic seal for the unit of the condenser, preventing brush leakage, and excluding moisture. This procedure is to be followed in the conUNIT Fig. 2. Ten plates of glass built up into a unit with alternate lugs connected in multiple