. The Bell System technical journal . Fig. la—Front view of measuring set. as for the preceding autumn, viz., the Holmdel Laboratory where ahalf-wave center-tapped antenna on a 65-foot (20-meter) pole was fedwith a simple parallel wire transmission line of No. 14 B & S gaugetinned copper wire, 1/4-inch () spacing, with 246ohms characteristic impedance. With the antenna impedance equal 200 BELL SYSTEM TECHNICAL JOURNAL to approximately 73 ohms the mismatch did not exceed 4 to 1 whichgave less than one decibel added loss over impedance matching.* Asa considerable wave-length rang
. The Bell System technical journal . Fig. la—Front view of measuring set. as for the preceding autumn, viz., the Holmdel Laboratory where ahalf-wave center-tapped antenna on a 65-foot (20-meter) pole was fedwith a simple parallel wire transmission line of No. 14 B & S gaugetinned copper wire, 1/4-inch () spacing, with 246ohms characteristic impedance. With the antenna impedance equal 200 BELL SYSTEM TECHNICAL JOURNAL to approximately 73 ohms the mismatch did not exceed 4 to 1 whichgave less than one decibel added loss over impedance matching.* Asa considerable wave-length range had to be covered, a single wave-length match was of no utility. An open-wire line of less than 250. Fig. lb—Rear view of measuring set with shielding covers removed. ohms impedance is not easy to construct. A thermocouple waslocated at the antenna connection, and the resulting direct current wasfed down the transmission line and filtered out by a choke coil—con- 4 Sterba and Feldman, Proc. L R. E., vol. 20, p. 1103, Fig. 12; July (10.^2). BellSys. Tech. Jour., July. 1932. ULTRA-SIIORT-WAVE TRANSMISSION PiIENOMENA 201 denser unit to operate the antenna meter. The antenna current wasof the order of ampere ordinarily. For the entire northwestern half of the horizon the nearby hills screened the country beyond from direct radiation com-ponents. The reception in these directions was thus entirely a diffrac-tion phenomenon. Fig. 2 gives the result of a cross-country transit 60 \ \ • MEASURED VALUE —INVERSE SQUAREDISTANCE CURV 1 S \^ — OF \ \ ~ \ • \ M N . ^^ . -s^ 1 • • • • • ^^ • • • _ • • •M* • ^^ •— ^ . 400 FEET
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
