192 AUSTIN: WIRELESS TELEGRAPHY NOTES 



2. Directive Action of the Marconi Bent Antenna at Clifden, 



Ireland 



While the directive action of the Marconi bent antenna at 

 short distances has been amply demonstrated by Marconi, Flem- 

 ing and others, it has not seemed certain that this radiation asym- 

 metry would not diminish as the distance increased so that at 

 great distances the radiation distribution would be the same as 

 that of an ordinary antenna. 



Recently at* the request of the wireless laboratory, the National 

 Electric Signaling Company made telephone shunt measurements 

 on the signals received at their Brant Rock station from the Mar- 

 coni transatlantic station at Clifden. These indicated an aver- 

 age received energy in the day time of 5 X 10~ 8 watts or in terms 

 of current through 25 ohms as used in Table XVI of my paper 

 already cited, 45 X 10 -6 amperes. I have been unable to obtain 

 from the Marconi Company any data on the value of the antenna 

 current at Clifden, but nevertheless some conclusions can be drawn 

 from the information at hand. The distance from Clifden to 

 Brant Rock is 2640 nautical miles. The height of the Clifden 

 antenna considered as a flat top is approximately 200 feet, the 

 effective receiving height of the Brant Rock umbrella antenna 

 was found in the recent long distance experiments to be approx- 

 imately 350 feet. The wave length of Clifden is a little more 

 than 6000 meters and the total available power is 1100 h.p. 3 



In Tables XVI and XVII already mentioned, h x = 200 feet, 

 h 2 = 350 feet, d = 2500 miles, in round numbers, and I r = 45 

 X 10~ 6 amperes. We may calculate from the tables that the 

 sending antenna current I s = 810 amperes which is an enormous 

 value. If the total antenna resistance is only 1 ohm it corre- 

 sponds to 660 K.W. which is more than the whole 1100 h.p. 

 would be able to transmit to the antenna. But this resistance 

 is improbably small. 



From this it must be concluded that unless the formula is grossly 

 in error the bent Clifden antenna shows a decided directive effect 

 even at this distance. 



3 Fleming, Principles of Electric Wave Telegraphy. 



