. An elementary manual of radiotelegraphy and radiotelephony for students and operators . wire not more than 001 mm. in diameter as the bolometer wireto be heated by tho oscillations, and detects and measures thisheat by the variation in resistance of the wire. With such anarrangement he states that he has detected electric waves at adistance of 40 kilometres from the radiator. 212 RADIOTELEGRAPHY E. A. Fessenden has devoted much attention to the improvementof thermal oscillation detectors, made as follows : An extremelyfine platinum wire, about 008 mm. in diameter, is embedded inthe axis of a
. An elementary manual of radiotelegraphy and radiotelephony for students and operators . wire not more than 001 mm. in diameter as the bolometer wireto be heated by tho oscillations, and detects and measures thisheat by the variation in resistance of the wire. With such anarrangement he states that he has detected electric waves at adistance of 40 kilometres from the radiator. 212 RADIOTELEGRAPHY E. A. Fessenden has devoted much attention to the improvementof thermal oscillation detectors, made as follows : An extremelyfine platinum wire, about 008 mm. in diameter, is embedded inthe axis of a silver wire, about 2 mm. in diameter, like the wickof a candle. The compound wire is then drawn down until thediameter of the platinum wire is reduced to about 00015 mm.,in the manner first suggested by \^ollaston. A short piece ofthis Wollaston wire is bent into a loop and the ends attached tostouter wires and enclosed in a glass bulb. If the tip of theloop is dipped into nitric acid, the silver coating is dissolved off,leaving a short length of exquisitely fine platinum wire sealed. Fig. 11. into the bulb like the filament of an incandescent lamp (seeFig. 12). The bulb is then closed and the air , the glass bulb may be enclosed in a silver bulb toshield it from external radiation. To detect the small rise intemperature produced in this fine wire by very feeble oscilla-tions passed through it, the ends of the loop are connected toa telephone, a single shunted cell being interposed. The cellthen transmits a feeble continuous current through the telephoneand the bolometer wire. If oscillations are then sent throughthe latter, they still further heat the loop and suddenly decreasethe currvint through the telephone. The ear then detects thisdecrease of telephonic current by a sound made in the telephone. OSCILLATION DETECTORS 213 1 1 foiuul timi in pluco of the pliilimiin wire a fine IuIh- Mth u lu^h rtsislimco li<jui»l conld I u enjploytxl, or even the t
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Keywords: ., bookcentury1900, bookdecade1910, booksubjecttelegra, bookyear1916
