High Frequency Apparatus Page 198

198 HIGH FREQUENCY APPARATUS end play in the motor, for if such were the case, the clearance between the discharge points could not be maintained at a uniform value. The Oscillation Condenser.—Before proceeding with the description of the condenser, it may be well to state that this particular feature of the outfit presents many difficulties in its design in view of the fact that the condenser is to be subjected to much rough handling and moving about. The data offered herewith is for a condenser having glass plates for its dielectric, but the author would suggest that this material, while highly satisfactory for use in a condenser to be used in but one place, is obviously subject to breakage and is at a further disadvantage from point of weight. Its use is suggested in this work merely because the stock is readily obtained and this at a low figure. Sheet mica, while several times as costly, is far superior in every way and its use is strongly recommended to those who feel that the extra expense is justified by the advantages gained, For the condenser proper, 120 sheets of 8 by 10 inch photographic glass will be required. This glass, in the form of discarded negatives, may be obtained from almost any photographer for a small sum. In addition to the plates above-mentioned, the builder will require some 24 plates additional to serve as cover glasses for each condenser unit. A few extra plates to replace possible broken or defective ones will not be amiss. The first operation will be to clean the emulsion from the glasses and this is readily done by soaking the plates in hot water. It is not essential that the plates be made perfectly clean of the emulsion if the plates have all been developed and the silver dissolved, but it is desirable to get the surface and particularly the edges for a space of an inch or more as clean as possible. The plates, when cleaned and dried, are to be placed in a warm oven prior to having