. Practical wireless telegraphy; a complete text book for students of radio communication . Fig. 238—Audibility Meter (American Marconi Company). Shunt resistance boxes are manufactured for this purpose and are termed audibility resistance coil is fitted with a multipoint switch and the contact studs are calibrated in termsof the audibility of the received signals as compared to the current corresponding to theleast audible signal with the particular telephone supplied with the meter. The type manu-factured by the Marconi Company of America is shown in Fig. 238. 218 PRACTICAL WIRELE
. Practical wireless telegraphy; a complete text book for students of radio communication . Fig. 238—Audibility Meter (American Marconi Company). Shunt resistance boxes are manufactured for this purpose and are termed audibility resistance coil is fitted with a multipoint switch and the contact studs are calibrated in termsof the audibility of the received signals as compared to the current corresponding to theleast audible signal with the particular telephone supplied with the meter. The type manu-factured by the Marconi Company of America is shown in Fig. 238. 218 PRACTICAL WIRELESS HIIC SJiJria taaorimo A typical chart* of the relative strength of signals received at different hoursof the day from the Marconi station at Ketchikan, Alaska, at the receivingstation at Astoria, Ore., is shown in Fig. 239. These readings were taken on aMarconi audibility meter. —H *Curve A, Fig. 239, shows the signal audibility throughout the 24 hours of the day from Ketchikanto Astoria. Curve _S shows the intensity of atmospheric electricity. It is interesting to note the distinctrise in both the signal and static intensity near to midnight and the distinct drop during the eariyhours of the morning. The rise of the peak is found to occur at approximately the same hour jnobservations taken over several months duration. PRACTICAL RADIO MEASUREMENTS. 219
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Keywords: ., bookcentury1900, bookdecade1910, booksubjecttelegra, bookyear1917
