146 



Popular Science Monthly 



Windings for Receiving-Tuner 



P. K., Somervillc, Mass., inquires: 



Q. I. Will a loose coupler having oval tubes 

 for the primary and secondary winding be as 

 efficient as one using round tubes? 



A. I. Yes, practically so. 



Q. 2. Which is preferable for the windings, 

 cotton or enameled copper wire? 



A. 2. Cotton wire is generally preferred to 

 enameled wire, but it is the general practice in 

 commercial apparatus to use single silk-covered 

 wire. 



Q. 3. Are No. 22 B & S and No. 32 B & S 

 wire correct for the primary and secondary of an 

 inductively-coupled receiving-tuner? 



A. 3. Yes, but generally No. 24 or No. 26 is 

 used for the primary winding. 



Detailed Dimensions of a 

 3,000-Meter Tuner 

 G. O. B., Kimbolton, Ohio, inquires: 

 Q. 1. Please give explicit instructions for the 

 construction of an inductively-coupled receiving- 

 tuner for all-around amateur work, taking 

 particular care to state the number of turns 

 necessary for the primary and secondary wind- 

 ings, also the number of taps to be taken from 

 these windings. 



A. I. For all-around amateur work, the 

 receiving-tuner should be responsive to wave- 

 lengths inclusive of 3,000 meters. The primary 

 winding should be 52 ins. in length by 5 ins. 

 in diameter, wound closely with about 300 turns 

 of No. 26 wire. The secondary winding should 

 be 5 ins. in length, 3;- ins. in diameter, wound 

 closely with 500 turns of No. 32 wire. The 

 inductance of the primary circuit may be altered 

 by means of a multipoint switch or by a sliding- 

 contact. It is customary to fit this winding 

 with two switches in some tuners. For example: 

 The first ten individual turns of the winding may 

 be connected to a ten-point switch; the remain- 

 ing turns are connected in groups of 10 to the 

 contact-points of a second switch. In this 

 instance you require a 29-point switch for the 

 groups of ten turns. The turns of the secondary 

 winding may be equally divided between the taps 

 of a ten-point switch. This secondary winding 

 should be shunted by a variable condenser of a 

 small capacity, say .001 microfarads, for tuning. 



Small Power-Transmitter 



G. W., KIk City, Okla., inquires: 



Q. 1. Will a spark-coil from an automobile 

 have sufficient power to act as a wireless trans- 

 mitter for a distance of two or three miles? 



A. I. Yes, provided the potential is sufficient 

 to jump a gap of at least J in. 



Q. 2. Will telephone induction-coils serve 

 the same purpose? 



A. 2. Generally, no. If the potential of the 

 secondary of the coil is sufficient to give a sm.dl 



spark-discharge, it may be used for extremely 

 short distance work, but not otherwise. 



Q. 3. Will a steel tower interfere with the 

 reception of messages if the aerial is attached 

 to it? 



A. 3. No, not if the wires are swung out at a 

 distance from the tower. 



Receiving Aerial 



W. L., Secaucus, N. J., writes: 



Q. I. Please advise if an aerial of four wires 

 20 ft. in length by 20 ft. in height has sufficient 

 dimensions to receive wireless telephone messages 

 with an ordinary telephone receiver and a 

 crystalline detector. 



A. I. To begin with there are no wireless 

 telephone transmitting stations in operation 

 from which you could receive signals. The 

 experiments at the Naval Station at Arlington 

 to which you probably refer were conducted on a 

 wavelength of 6,000 meters. Your aerial is 

 entirely too small for adjustment to long waves. 

 A single wire from 500 to 800 ft. in length could 

 easily be loaded to a fundamental wavelength of 

 6,000 meters. 



Long Wave Receiving Tuner 



P. A. J., Jr., Suffolk, Va., writes: 



Q. I. I propose to wind the coils for a 

 receiving tuner on two tubes; one is II ins. in 

 length by 6 ins. in diameter and the second 12 ins. 

 in length by 5 ins. in diameter. What size wire 

 should I use and to what range of wavelength 

 will it be adjustable? 



A. I. Use the ii-in. tube for the primary 

 winding and cover it with No. 24 S.S.C. wire. 

 Connected to the average amateur aerial, it will 

 permit adjustments inclusive of 6,000 meters. 

 750 feet of wire are required for this winding. 



The secondary w inding requires approximately 

 1,250 feet of No. 30 S.S.C. wire. Connected in 

 shunt to a small variable condenser, it will 

 respond to wave lengths between 8,000 and 

 0,000 meters. 



Licensing of Sending Stations 



R. D. S., Ripley, Okla., inquires: 



Q. I. With a transmitting set composed of a 

 i-in. spark-coil, small oscillation transformer and 

 glass plate condenser, wovdd I recpiire a U. S. 

 license if my station is located 65 miles from the 

 State Line and 15 miles from the nearest radio 

 station which is a college ex])erimenlal station 

 located at -Stillwater? If a license is required 

 please give the necessary instructions for 

 obtaining it. 



A. I. During the daylight hours the range of 

 this ai)paratus will not exceed 20 miles and in 

 consequence a license is not required. It is 

 equally probable that the signals from this 

 station will not extend over the State Line 

 during the night hours. 



