What Radio Readers Want to Know 



A Tikker Receiver and How it Works 



C. M., Indianapolis, Intl., inquires: 



Q. I should like some information concerning 

 the "tikker" for the reception of undamped 

 oscillations. I have heard considerable regarding 

 continuous waves but so far have not been able 

 to ascertain just how a tikker is constructed. 



A. However constructed, the tikker is nothing 

 more than a circuit interrupter arranged to open 

 and close some portion of the receiving tuner 

 circuits at a rate of 200 to 500 times a second. 

 The original Poulsen tikker consisted of two light 

 gold wires, one of which was attached to the 

 vibrating member of an ordinary buzzer which, 

 when set in operation, interrupted the circuit 

 from the secondary winding of the receiving 

 tuner to the telephones. At a later date another 

 form of tikker was devised which consisted of a 

 toothed wheel driven by a small motor and in 

 contact with a brush. 



The very latest type of tikker is known as a 

 "slipping-contact detector." Of simple con- 

 struction, it comprises merely a grooved wheel 

 (with a perfectly smooth surface) rotated at a 

 speed of say 1000 revolutions per minute. A 

 small piece of thin steel wire is placed in light 

 contact with the groove. The constant gripping 

 and slipping of the wire during rotation causes a 

 variation of the accumulated energy in the tele- 

 phone condenser, thus setting up audible pulses 

 of current in the telephone circuit. 



The tikker, regardless of the type of construc- 

 tion, occupies the same position in the secondary 

 circuit of the receiving tuner as the crystal de- 

 tector, but generally the secondary winding is 

 constructed of Litzendraht to give a circuit 

 having a minimum value of damping. 



Range; Aerials; Quenched-Gap 



D. P. D., Limon, Colo., asks: 



Q. I. Will an aerial 100 ft. in length by 50 ft. 

 in height be satisfactory for receiving messages 

 from coast stations with 1000 to 1500 miles of 

 mountainous country intervening? The local 

 conditions for this work are good, since there are 

 no high buildings or hills in the immediate 

 vicinity. This aerial will have an altitude of 

 56(K) ft. above the sea level. Will I be able to 

 receive ship stations with it? 



A. I. If receiving apparatus of the vacuum- 

 valve amplifier type is installed little difficulty 

 should be experienced in receiving signals from 

 the coast stations during the night hours. 



Q. 2. Docs a series condenser cut down the 

 sending distance of a transmitting set? 



A. 2. Speaking generally, it has the effect of 

 cutting down the flow of current in the antenna 

 system and therefore reduces the range. The 

 insertion of a series condenser generally has the 

 effect of increasing the total resistance of the 

 antenna system. 



Q. 3. Will an aerial 50 ft. in length by 40 ft. 

 in height, composed of 4 wires spaced 3 ft. apart, 

 be satisfactory for transmitting 100 miles using 

 a. I. k. w. closed-core transformer and a rotary 

 spark-gap? 



A. 3. It will be rather difficult to consume the 

 full output of this transformer at a wavelength 

 of 200 meters because the capacity of the con- 

 denser cannot exceed o.oi mfd. If the receiving 

 station is fitted with suitable apparatus you will 

 experience little difficulty in covering the desired 

 distance at nighttime. During the daylight 

 hours we should prefer a 2 k. w. or 5 k. w. 

 transmitting set operated at an increased wave- 

 length. 



Q. 4. Which is considered the more efficient, 

 a rotary-gap or a quenched-gap when the neces- 

 sary high potential is obtained from the i k. w. 

 transformer? 



A. 4. The quenched-gap may be made the 

 more efficient electrically, provided the trans- 

 mitting apparatus is harmoniously designed 

 throughout. A well-designed quenched-gap 

 transmitter has a specially constructed motor 

 generator and transformer. The range of the 

 average amateur station will be increased by 

 the use of a quenched-gap provided certain pre- 

 cautions in the design of the apparatus are 

 observed. For example, the oscillation trans- 

 former should be so constructed that the in- 

 ductance value of the primary and secondary 

 windings can be regulated inch by inch. Like- 

 wise the degree of coupling between the primary 

 and secondary windings must be very closely 

 adjustable. 



The potential of the transformer requires 

 careful regulation. In motor generator sets this 

 is accomplished by means of the generator field 

 rheostat, but where the energy is taken direct 

 from the city mains it may be necessary to 

 supply a transformer having variable tap-olTs 

 in the secondary winding, in order that the cor- 

 rect value of voltage may be obtained. In addi- 

 tion, the high potential transformer must be one 

 that possesses considerable magnetic leakage. 

 If of the closed-core type, it should be fitted with 

 a magnetic leakage gap. The open-core trans- 

 former naturally possesses this characteristic. 

 If you are not wholly familiar with the design 

 and requirements of the quenched-gap dis- 

 charger, the rotary-gap is recommended on ac- 

 count of its simplicity, easy construction, and 

 permanence of adjustment. 



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