Popular Science Monthly 



633 



Non-directional 

 antennae 



Mechanica 

 switch 



Section of Telefunken-compass sending station. Six- 

 teen such sets form the aerial shown on page 632 



On page 451 and following of the March 

 1916 number, Popular Science took up 

 and discussed at considerable length two 

 radio directional systems, the Bellini-Tosi 

 and the Telefunken, by which ships at sea 

 could find their way along coasts and into 

 harbors in spite vVire connecting non-direction- ^ 

 of fog or blind- a! antennae to switching 

 ing storms. It machine V 



is this appara- 

 tus which has 

 evidently been 

 adapted exten- 

 sively to war 

 Zeppelins. 



In wireless, 

 parallel anten- 

 nae give the 

 strongest sig- 

 nals; those at right angles, the weakest. 

 It is this principle which makes all radio 

 direction-finding possible. 



In the Bellini-Tosi system the moving 

 station sends signals to a fixed station, and 

 the fixed station, by special apparatus, de- 

 termines the direction of the sender and 

 thereupon transmits the information to 

 the sender by radio. Under the Tele- 

 funken plan, the moving station deter- 

 mines its own position, powerful signals 

 ha\ing been sent out from fixed stations 

 along shore. This seems to be the better 

 arrangement, as it is more practicable te 

 have powerful stations on shore than 

 aboard an airship. The signals can 

 radiate out over longer distances, the 

 sending station can be entirely autom.atic, 

 and on board the airship the commander 

 need only listen for loudest signals (or 

 weakest, v.hichever he prefers), hold a one- 

 handed stop-watch — hereafter described 

 —in his hand, and he gets his direction 

 almost at once. No doubt the many 

 war Zeppelins which have ventured 

 out over England have used this system. 

 Details of the whole plan are interesting. 



The powerful sending stations in Ger- 

 many have thirty-two very long, slanting 

 antennae radiating from a tall central 

 mast. These antennae are the exact 

 equivalents of the rays to be found on 

 every ship's compass, and, like them, 

 represent the thirty-two fixed points of 

 the compass. A mechanically operated 

 switch connects with opposite pairs of 

 these separate aerials once every thirty 

 seconds. A single telegraphic . dot is 



fiashed out at each connection. In this 

 way all points of the compass are reached 

 every half-minute. 



Any German aircraft, whether it is a 

 Zeppelin or a small reconnaissance bi- 

 plane, is able to pick up these dots, and by 



this means it 

 can determine 

 its direction 

 relative to 

 the sending 

 station. No 

 other addition 

 to its regular 

 receiving appa- 

 ratus is re- 

 quired. How- 

 e v e r a 

 calibrated 



Cable connecting all directional 

 antennae to switching machine 



pocket stop watch must be referred to. 

 By "calibrated" we mean that the hand of 

 the watch runs like the previously de- 

 scribed switch, and that it makes a 

 complete revolution around the dial in 

 thirty seconds. The dial is, of course, 

 marked like that of a navigator's com- 

 pass with the usual thirty-two points 

 instead of with ordinary minutes and 

 seconds. 



The plane de'lerminecl 

 ^ N 



5topwatcK dia 



Rotating 

 switch at the 

 sending sta- 

 tion. It and 

 watch -h and 

 lineuptoindi- 

 cate position 



At left is the 

 one- handed 

 watch comman- 

 der on Zeppelin 

 carries. Four 

 sample positions 

 shown. "Strong- 

 est signal ' ' points 

 to home station 



N Start 



5 Strongest 

 signal ^ 



signal 



A^i^■onA^tic switch 



\ 



Since commander's watch-hand and the send- 

 ing switch rotate ?n unison, loudest signal 

 determines plane in which sender is located 



Apparently the Zeppelins using the 

 Telefunken-compass are equipped with 

 ordinary non-directional aerials for re- 

 ceiving the signals. 



