616 



Popular Science Monthly 



Experience and observation have shown 

 that the "X" grade Hudson filament 

 bulbs are the most satisfactory and 

 economical. 



Once the proper adjustments are dis- 

 covered, the setting will be practically a 

 constant for a stated wavelength, and it 

 wuU likely be found that all the un- 

 damped wave stations mentioned may be 

 tuned to maximum strength of signals by 

 slight changes in the capacity of con- 

 denser II, perhaps tuning up condenser 

 3 for Sayville. 



The continuous-wave stations are 

 heard in clear, flute-like tones, the pitch 

 of which may be varied in a wonderful 

 and amusing manner by slight change of 

 condenser 8 or ii, or both, or the prima- 

 ry of the tuner, or inductances 13 and 14, 

 or simply touching a metal part of the 

 secondary circuit. 



Particularly close tuning with arc 

 stations is necessary, since usually two 

 waves of practically equal energy but of 

 slightly different length are emitted. 

 One of them (the main wave) represents 

 the dots and dashes and the other (the 

 compensation w'ave) represents the 

 breaks. Some difficulty may be ex- 

 perienced in entirely suppressing the 

 compensation wave, but the difference 

 between the two may always be made 

 sufficient for clear reading. 



With this set the phenomenon of 

 "stepped-up" voltage of the high-poten- 

 tial battery may be taken advantage of 

 to procure a further increase in volume 

 of signals of spark stations. Arlington's 

 spark signals may be brought in to a 

 degree of loudness painful to the ear- 

 drums by throwing in all of the tuner 

 inductances, all of the secondary loading 

 inductance and all of inductance 14, 

 condenser 11 remaining at zero. South 

 Wellfleet (WCC) can be made to "come 

 in" like a grandfather bullfrog by 

 similar manipulation, making due allow- 

 ance for the shorter wavelength. The 

 same is true, generally, of spark stations 

 anywhere within reach, that work on 

 1000 meters wavelength or over. A far 

 distant and relatively weak spark station 

 may come in, not with the true note, but 

 with a "whisper" effect. It is usually 

 not practical to obtain perfect oscillation 

 of the audion, resonance with and 

 amplification of signals from stations 



using wavelengths of 600 meters and 

 under, because of the circuit difficulties 

 involved. 



The experimenter who sets out to rig 

 up a receiving set of this character is 

 urged to avoid loose connections, im- 

 perfect contact at switches, bunched and 

 parallel connecting wires as much as pos- 

 sible, and sloppy work generally, and to 

 employ persevering patience in tuning 

 the set to various stations until adept- 

 ness is acquired. All switch handles 

 should be of good insulating material, 

 and no part of the operator's body should 

 be allowed to come into contact with 

 binding posts, switch levers or bare 

 wires; the capacity of the body will 

 prevent delicate adjustment. The in- 

 ductances and condensers of the three 

 circuits should be kept separate, each 

 circuit a reasonable distance from the 

 other, say a foot. Proper allowance 

 must be made for the fact that signals 

 that may be coming in ever so clearly 

 may sometimes be almost or entirely 

 suppressed by placing the hand or arm 

 close to certain of the coils or condensers, 

 or even close to the connecting wires. 

 This is particularly true of undamped 

 signals being received on a lower har- 

 monic of the true wave. 



Just a few words about winding the 

 coils with the finer wire: Use a lathe, if 

 available, or improvise one with a tool 

 grinder, replacing the grinding wheel 

 with a circular block that will just fit 

 inside the tube; one tack will hold the 

 tube to the block. A similar block, sup- 

 ported and free to turn on a stud, will 

 hold the other end of the tube. By lo- 

 cating the spool of wire on a rod about 

 25 to 50 ft. away and starting the wind- 

 ing carefully, the whole tube may be 

 wound in a few minutes at high speed; 

 the wire will "feed" itself, barring acci- 

 dent. The taps may then be brought 

 out by lifting the proper turns with the 

 point of a knife blade, cutting the wire, 

 unwinding a turn of each end, twisting 

 them together and soldering the bare 

 ends. The tubes may be w^ound with 

 the coarser wire by hand and taps 

 brought out as they are reached in 

 winding. Any experimenter whose wire- 

 less is equipped to receive undamped 

 waves, should be able to obtain very in- 

 teresting and valuable results. 



