194 ANNUAL KEPORT SMITHSONIAN INSTITUTION, 1908. 



Glace Bay, Nova Scotia, and Clifden, Ireland, a distance of more 

 than 2,000 miles, the frequency being approximately 70,000. The 

 same messages were received at Brant Rock, Massachusetts, a distance 

 of nearly 3,000 miles. 



Still more recently Captain Hogg, of the " Glacier," has written 

 that during the southward passage of the Pacific fleet he received 

 messages from the station at Brant Rock, Massachusetts, while oil' 

 Cape Ste. Roque, Brazil, South America. The frequency used for 

 sending was approximately 80,000, and the messages were received 

 with the very interesting and sensitive silicon receiver invented by 

 Mr. Pickard. This distance of 3,000 miles is the greatest yet achieved 

 by wireless transmission during daylight, and would indicate that 

 with the use of suitable high towers much longer distances can be 

 reached. 



RANGE OF WIRELESS TELEPHONY AND WIRELESS TELEGRAPHY COMPARED. 



For the same power it is possible to telegraph to a farther distance 

 than to telephone. Distinct speech depends upon the presence of 

 harmonics of a frequency as high as 1,200 per second. The amplitude 

 of these harmonics is, according to some rough experiments made by 

 the writer, only . about 1 per cent of the fundamental f requenc3^ 

 Consequently, with a perfectly modulated transmitter, one hundred 

 times as much energy would be necessary to telephone a given distance 

 as to telegraph. It fortunately happens, however, that a carbon 

 transmitter and also the circuits in Avhich it is used, can be so con- 

 structed as not to modulate perfectly, but can be arranged so as to 

 accent the higher harmonics. 



With transmitters arranged for the purpose good transmission has 

 been obtained with thirty times the energy required to produce audi- 

 ble telegraphic signals. By still further modification the power re- 

 quired has been reduced to approximately ten times that necessary 

 for telegraphing, curiously enough without noticeably distorting the 

 character of the speech. There is one fact, however, which prevents 

 the ratio from being as large practically as the instruments show, 

 i. e., speech can be satisfactorily understood with a less increase of 

 power above a minimum audibility than telegraphic signals. 



The amount of power necessary for wireless telephony may there- 

 fore be taken as approximately five to fifteen times that necessary 

 for wireless telegraphy, i. e., under the same circumstances and for 

 the same power the wireless telegraph will carry two to four times 

 as far. The difference in range would be very much greater also but 

 for the curious fact that there is much less falling off with sustained 

 oscillations than with intermittent groups of waves, even though the 

 frequencies are identical. 



