6^8 



Popular Science Monthly 



Induction from Streetcars 



F. M., Washington, Ind., writes: 



Q. I am about to purchase certain wireless 

 telegraphy instruments, but inasmuch as my 

 receiving aerial will be located near a streetcar 

 line and powerhouse I desire to know what 

 effect these wares will have on the reception of 

 signals? 



A. Although you may expect to receive inter- 

 fering sounds from these wires due to electro- 

 static induction, they will not wholly prevent 

 the reception of signals. If possible, place the 

 receiving aerial at right angles to the power line. 



Receiving-Tuner Doubts Cleared Up 



W. B. H., Fresno, Cal., inquires: 



Q. In the December, 191 5, issue you give cer- 

 tain dimensions for an inductively-coupled re- 

 ceiving tuner to cover a range of 1500 meters. 

 The statement is made that the primary and 

 secondary windings should be made of No. 28 B. 

 & S. fage copper wire. To me this seems incor- 

 rect. I cannot understand how the secondary 

 voltage will be any different from that of the 

 primary if the same size of wire is employed. 

 Before commencing the construction of such a 

 tuner I should like to have this matter cleared 

 up. 



A. It is perfectly feasible to cover the primary 

 and secondary' of the receiving tuner with the 

 same size of wire. For the average crystal de- 

 tector it is customary in some forms of com- 

 mercial apparatus to use No. 32 S. S. C. wire on 

 the secondary. A step-up ratio of turns in an 

 oscillation transformer does not necessarily 

 mean a stepping up of voltage, since there are 

 other factors which must be taken into considera- 

 tion. Please understand that the actual wave- 

 length to which the tuner described in the 

 December, 1915, issue will be adjustable depends 

 upon the capacity of the condenser in shunt to 

 the secondary winding. With a secondary 

 winding 5 ins. in length by 4J ins. in diameter, 

 covered with No. 32 wire and shunted by a con- 

 denser of o.ooi m.f. capacity, the tuner will be 

 adjustable to wavelengths in the vicinity of 

 4000 meters. 



Where to Place Receiving Aerials 



R. P. C, Nineveh, N. Y., asks: 



Q. I wish to construct an aerial 60' in height 

 by 200' in length. Our buildings are surrounded 

 by hills. In which location do you think I would 

 achieve the better results for receiving purposes, 

 namely, by suspension of the wires on 20' 

 poles atop of the barns which are 40' in height, 

 or by placing them on 60' poles upon the hill, 

 which is 200' above the barns? Our elevation is 

 1145' above the sea level. Approximately over 

 what distance may I expect to receive messages? 



A. For general work we should prefer to erect 



the aerial on the hill, provided that the receiving 

 apparatus can be housed in the immediate 

 vicinity of the aerial. The actual distance over 

 which messages may be received depends en- 

 tirely upon the type of receiving apparatus in 

 use. With the average amateur equipment 

 fitted with a crystalline detector you should be 

 enabled to copy messages at nighttime during 

 the favorable months of the year from all com- 

 mercial stations located on the Atlantic coast 

 and Gulf. With an extremely sensitive long 

 distance set, say one employing a regenerative 

 receiving circuit in connection with the audion, 

 you should experience no difficulty in receiving 

 messages from the radio station located at 

 Nauen, Germany. 



A Receiving- Condenser for 1500-Meter 

 Loose-Coupler 



W. M. K., Windsor, Ont., inquires: 

 , Q. I. I should like to put this department to 

 trouble again by asking for information concern- 

 ing the size of a receiving condenser for a 1500- 

 meter loose-coupler. Approximately how many 

 tinfoil sheets should be used and what are the 

 required dimensions? 



A. I. We assume that reference is made to 

 the fixed condenser in shunt to the head tele- 

 phones. Two sheets of tinfoil 30 ins. in length 

 by 2h ins. in width, separated by a thin piece of 

 paraffin paper and rolled up on circular form, 

 will give a sufficient value of capacity for the 

 average requirements. The variable condensers 

 must be of the air dielectric type such as supplied 

 by electrical supply houses advertising in the 

 columns of this magazine. 



Q. 2. Approximately over what distance can 

 I receive with this set connected to an aerial 

 90 ft. in length and 50 ft. in height at both ends, 

 keeping in mind that the tuner is adjustable 

 to a wavelength of 1500 meters? 



A. 2. During the nighttime this apparatus 

 should be responsive to stations 1000 to 1200 

 miles distant. The daylight range is proble- 

 matic. 



Sustained Waves and Government 

 License 



H. W. D., Jr., Schnectady, N. Y., asks: 



Q. I. May an amateur make use of a set 

 responsive to an undamped wave? 



A. I. There are no regulations governing the 

 type of receiving apparatus employed at the 

 amateur station. If an undamped oscillation 

 transmitter were employed it would be necessary 

 to secure a U. S. station license. 



Q. 2. What is the fundamental wavelength 

 of a four-wire aerial 120 ft. in length, 45 ft. in 

 height at one end and 50 ft. at the other with a 

 lead-in of 25 ft. placed at an angle of 70 degrees 

 to the aerial? 



A. 2. The natural wavelength of this antenna 

 is approximately 320 meters. 



