. The principles underlying radio communication . ime. The anode may not require renewalfor a considerable length of time; its life is greatly lengthenedby proper cooling and the use of pure water in the circulatingsystem. The carbon cathode will usually serve for about 24hours continuous burning. The sizes of the carbons for afew arcs are, for a 2-kw. arc, diameter | inch, length 8 inches;for a 5-kw. and other medium-sized arcs, diameter f inch, length10 inches; for arcs larger than 100 kw., diameter If inches,length 12 inches. The rate of consumption of the carbon de-pends on the chemical co
. The principles underlying radio communication . ime. The anode may not require renewalfor a considerable length of time; its life is greatly lengthenedby proper cooling and the use of pure water in the circulatingsystem. The carbon cathode will usually serve for about 24hours continuous burning. The sizes of the carbons for afew arcs are, for a 2-kw. arc, diameter | inch, length 8 inches;for a 5-kw. and other medium-sized arcs, diameter f inch, length10 inches; for arcs larger than 100 kw., diameter If inches,length 12 inches. The rate of consumption of the carbon de-pends on the chemical composition of the gas in the arc chamber. The carbon electrode is so mounted that it can be screwed inand out for the purpose of striking and adjusting the arc. The ARC CONVERTERS. 409 length of the arc flame is adjusted by moving the carbon elec-trode to secure maximum antenna current. Practical Operating Characteristics.—When an arc trans-mitter is properly adjusted for operation, the antenna current Counterpoise. Upper Field. JCerojene Mtu^inaMeeL. ■ lotrer FieldWin din if. Fig. 226.—100-k\v. Federal arc converter, with casing removed. is of the current supplied to the arc. Under theseconditions, it is not necessary to place an ammeter in the an-tenna circuit to determine the antenna current. It has beenfound that for arcs rated from 15 kw. to 100 kw. the antennacurrent is, very closely, one ampere per kilowatt of rating whenthe arc is properly adjusted for operation. The efficiency of an 410 TRANSMITTING APPARATUS. arc in converting power into high-frequency oscillationsseldom exceeds 50 per cent; the remainder of the power sup-plied is largely dissipated in the arc chamber in the formof heat, and provision must be made for conducting the heataway and for preventing excessive temperatures in the arcchamber. If an arc could be adjusted so that the voltage wave and thecurrent wave were sine waves, the effective value of the alter- ALC
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