. Elements of radio telephony . se,dust, and dirt and allows an unobstructed view of the crystalsurface at the same time. Single Circuit Receiver with Crystal Detector.—A diagramshowing the usual connections is given in Fig. 29. Theincoming signal sets up a voltage in the antenna and this inturn produces a current which flows through the circuitcomprising the antenna, tuning coil L, condenser C, andground connection. The tuning or inductance coil is usuallyadjustable either by a provision for changing the number ofturns included in the circuit or by the addition of anothersmall coil connected
. Elements of radio telephony . se,dust, and dirt and allows an unobstructed view of the crystalsurface at the same time. Single Circuit Receiver with Crystal Detector.—A diagramshowing the usual connections is given in Fig. 29. Theincoming signal sets up a voltage in the antenna and this inturn produces a current which flows through the circuitcomprising the antenna, tuning coil L, condenser C, andground connection. The tuning or inductance coil is usuallyadjustable either by a provision for changing the number ofturns included in the circuit or by the addition of anothersmall coil connected in series with the main coil and arranged 62 ELEMENTS OF RADIO TELEPHONY SO that it may be made to rotate inside the larger coil. Thischanges the mutual inductance between the two coils andhence varies the wave length by a variation of the 2M termin the expression for wave length given on page 58. Thistype of variable inductance coil is commonly known as avariometer and is illustrated in Fig. 30. Another illustration Antenna,. Phones Fig. 29.—Simple crystal detector receiving set. of this type of variable inductance coil can be seen in Fig. 39,which illustrates a set employing a single circuit receiver ofdifferent characteristics. In operating a set of this character the movable contactin the crystal detector is brought into contact with thestationary crystal and adjusted to its most sensitive condi-tion by moving it slightly while listening in the telephonereceivers. There will usually be enough noise of one kind RECEIVING EQUIPMENT 63 or another present in the antenna circuit to adjust the pointalthough in some sets a small high-pitched electric buzzeris provided to set up an artificial signal in the antenna the crystal detector is carefully adjusted to its mostsensitive condition the set is ready for tuning. This isaccomphshed by varying the inductance coil or condenserover the entire available range, hstening meanwhile for the
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectradio, bookyear1922
