Popular Science Monthly 



G25 



ground and also with the aerial, in 

 scries with a hot-wire amnietcr. The 

 secondary should then be adjusted until 

 the maximum radiation is obtained. The 

 aerial and ground siiould then be dis- 

 connected, the condenser increased by 

 one plate and the [)rimary again tuned 

 to 200 meters. The secondary is again 

 connected and adjusted for maximum 

 radiation. This should be continued 

 until the condenser is all in use. A 

 table must be made with spaces for 

 entries of each set of adjustments, and 

 the set finally adjusted according to the 

 combination which gives the highest 

 radiation. 



The adjustment marked X would be 

 used, according to the table, since it 

 gives maximum radiation current. In 

 receiving, I have noticed that the chief 

 trouble is interference. The ability to 

 tune out one station and still hear 

 another whose wave is nearly the same 

 as the first, is a coveted ideal, especially 

 since all the amateurs are on one wave, 

 all the commercials on another, etc. A 

 considerable advance in sharp tuning 

 comes with the use of an audion-detector, 

 since with this type of detector the 

 operator must tune sharply if he wishes 

 to hear anything at all. Another useful 

 way of obtaining sharp tuning is by 

 inserting a variable condenser in series 

 with the aerial. By using large induc- 

 tance in the primary and small series 

 capacity, it is often possible to eliminate 

 much local interference and still hear 

 the desired station readably, although 

 jierhaps not as loud as with the straight 

 primary. 



If a loose coupler is handled intelligent- 

 ly, and the coupling between its coils is 

 adjusted carefully, it will get rid of a lot 

 of interference. A small condenser 

 placed in shunt with the loose coupler 

 secondary is always of assistance on 

 the longer waves, such as those from 

 600 or 1,000 meters up. A sample 

 table is shown in Fig. 4. 



Many amateurs pay too little atten- 

 tion to their ground connection. It is 

 fully as important as the aerial. A 

 ground which I have been using for 

 over a year with the best of results is 

 made of a */iG-in. sheet of copper, 

 4 by 6 ft., buried 10 ft. underground. 

 Connection is made to this sheet by a 



No. 4 bare copper wire. This size wire 

 is required by the Fire Underwriters, for 

 both lead-in and ground-lead, and besides 

 satisfying their retiuiremcnts, it is a 

 help towards good transmitting results 

 on account of its high conducti%'ity. 



Many of the aerials seen as one goes 

 through the city are not constructed 

 with any idea of what their wavelength 

 will be, or of which type of aerial is best 



for the work desired, etc. For 200- 

 meter work, the "T" type aerial is 

 probably the best. It can be made 

 almost double the length of an "L" 

 aerial having the same wavelength, 

 thus giving increased aerial capacity. 

 A three-wire "T" type aerial 100 ft. 

 long, not too high, has a fundamental 

 wavelength which will be about right 

 when used with sufficient oscillation- 

 transformer secondar>' to bring the 

 emitted wave up to 200 meters. Enough 

 secondary may be used to insure good 

 transference from the closed to the 

 open circuits with an aerial of this kind. 

 The wires should be spaced 3 or 4 ft. 

 apart. 



If an amateur's wireless set is given 

 careful study in its design and careful 

 work in its tuning and adjustment, there 

 is no reason why, with operators of 

 ^ by I K.W. input it should not do the 

 long distance work that is being achieved 

 by the few operators who have given 

 their outfits careful study. 



Removing Old Putty from a Window- 

 Pane with a Hot Iron 



A HOT soldering or other iron run 

 over old putty will soften it so that 

 its rcmo%'al can be easily accomplished 

 with a knife or chisel. Care should be 

 exercised that the glass is not heated 

 enough to cause it to crack. 



