High Frequency Apparatus Page 37

THE OSCILLATION CONDENSER 32 37 MOULDED Fig. 3.-One section of moulded condenser struction of every condenser described in this work with the exceptions specifically noted. Mica Condensers.-The use of mica as the dielectric for the condensers of portable high frequency apparatus cannot be too strongly recommended. The material is light in weight and it is possessed of electrical properties that render it admirably adapted to the purpose. Electrical mica is costly, however, and as the size of the sheets increases, the cost goes up in proportion; but the price is not prohibitive if light-weight is an important consideration. The mica may be obtained in small sheets of almost any desired thickness. The method of assembly is identical with that of glass. Moulded Condensers.-This type of condenser is not within the reach of the amateur constructor's shop equipment as its manufacture requires the use of very expensive dies and presses capable of exerting enormous pressure. The moulded condenser may be purchased outright, however, in sections having a capacity of .002 mfd. each. The moulded condenser is mechanically strong—indeed, it is practically unbreakable. The conducting material is of copper in sheets approximately five inches square and