Show use of wave trap for good results part Is serviceable even in loop receiver radio expert says by JAMES H CARROLL institute of cadlo in radio world from all quarters of the compass come inquiries as to wave traps and their uses and as to what Is the best type of trap to use tor good results evidently there la a great interest in this bandy little apparatus especially under present conditions and even when the air Is eventually cleared a wave trap still will be a good thing to have around take as ai example the solenoid wave trap as represented by the WEB model there are two main reasons theoretically cally tor the success of this kind of trap and one Is because of the solenoid winding which enables the electrical currents flowing through it to establish a more evenly balanced set of lines of force which concentrate themselves in the center of the tubing and upon the concentration point 0 the variable condenser in this type of wave trap it has been discovered that this makes for efficiency and has a great deal to do with tuning micrometer adjustment of interfere Int erfer ence elimination Is necessary tor circuits therefore when using a wave trap of this variety the condenser plates will be pressed very slowly or the operator will not trap out the unwanted station this Is a point in favor of such a trap wave traps of this type can be et used in many different places if vou have been unfortunate in obtaining good results with a wave trap you may not have used it in the right place in other words you may have inserted it in your aerial circuit when it would give you the best re suits in your ground circuit or some other place instead in the aerial circuit let us first try the aerial circuit disconnect the aerial from your set and connect it to one of the posts on your wave trap with a short wire connect the other post of the trap to the aerial post of your set from whence you previously removed the aerial this Is the simplest and most usual use of a wave trap and it la a good one but under certain conditions it will not prove the most effective if by this method we do not succeed in perfectly eliminating an offending station on the lower wave lengths let us try inserting our trap in the ground circuit this Is done in the same way except that we substitute the ground wire tor the aerial wire this meant Is especially recommend ed for efficient low wave elimination but reports show that it alo works equally well with the highest wave lengths and that also by this method additional stations have been tuned with a wave trap of the design we are discussing now it we are working with a loop we can connect our trap in the grid circuit the most approved method of eliminating interference in such a case and the only way of using a wave trap with a loop set first locate your grid wire that goes to the tuning device in your set either coll or condenser disconnect this wire at the point of contact with the grid post of the socket connect it to one end of a flexible wire about two feet long connect another piece of flex ible wire of the same length at the place from which disconnected the other wire and run these two wires outside bour set to your wave trap attaching one wire to one post of the trap and the other 0 o the other post of the trap you are now ready to eliminate interference this meth od even if it Is a little more troublesome to try out Is well worth while because it will meke any set alve another means may be used another means we may use 13 the aerial and ground shunt which Is one of the oldest methods known and among the most popular all that need to be done to use this method of insulation Is to run a wire from the aerial post of the set without discon the aerial wire to one of the posts of the wave trap then run another wire from the ground post of the set to the wave trap although no tuning can be done with a wave trap used in this wiy it functions as an excellent trapping and sta lions in the vicinity of the set can be dominated by this means do not confuse a wave trap of this type with an apparatus such as the centra lab short wave selector which Is what the name implies and not a wave trap it fills a very definite function of its own and can be used very satisfactorily in conjunction with a trap of the type we have selected as the best our testing was being done and before this article was compiled com pled a letter came to hand from a fan sign ing himself a junior cadlo bug ask ing for practically the information given in this text and among other things inquiring as to what became of the tripped station when it was cap aured probably figuring that it re malnee in the trap ind beating its giaves ni rt rt walls in a futile effort to escape well junior you have staggered us here as we the slightest idea na to what becomes ot the invading station our idea Is that perhaps getting its nose or its tall pinched in the trap it tears away on the trail of other prey in the form of sets not protected by a beneficent wave trap rhe earliest form of trap of any kind known to history was a pit dug in the ground by the caveman in front of hla cave apartment this waa covered by twigs branches and grasses so that it looked like a solid surface along came the marauding ma mammoth la search of meat to vary his vegetarian diet and tumbled in with a crash that shook the row of caves and dislocated every aerial in miles then all that remained for mr caveman and his tribe was to squat around the trap and sing and bowl in chorus on they ang the threshing behemoth to death in which case they became the partakers par takers of meat it Is evident then that the inventor of the wave trap modeled it upon this efficient device taking a hole or a pit as it were enclosing it in bakelite dig it with a solenoid winding and adding the pinching condenser that squeezes the invading station until it howls for mercy an easily made coil cheap and efficient quite often in his experimenting a radio fan needs a coll that Is easily made cheap and efficient the materials needed for this coll are an erdl nary drinking glass some iso 24 D S C wire a roll of tape four fahne stock clips and a piece of thin wood such as may be obtained from a box the wood should be cot to 11 by 4 inches and then placed across th middle of the open end of the tumbler dauble a piece of the tape and wrap 1 GLASS JAR 7 colt wound on tumbler will greata reduce losses tightly across the glass and over the wood then double another piece of tape and place it over th glass and wood so that it divides then into four equal parts bend the dept in the middle and round them a so that they will fit against the of the glass slip atre ends of the clip under the tape and to their end the wire the coll can then be mount ed by means of holes drilled in th wooden base if the wire Is wrapped tightly around the glass and tap there will be no danger of its olt and the coll will be found to b an efficient one ilailo news used aerial lead fish to pick up the message ahen the two way radio apparatus failed observers on the ground were perplexed as to how they could glae instructions to occupants of an airplane during army maneuvers bayt popular mechanics the problem was by tang the als patch in a tobacco ack weighted with small stones and attaching that to a string about twenty feet long which was held taut by two men the pilot informed by the panel agnal to stand by for instructions descended cloa enough to see what was going on then returned presently with the ra dlo antenna unreeled As he approached pro ached the men holding the string he throttled the engine allowing the lead fish at the end of the aerial to hang more nearly vertical it caught the cord and the message was hauled into the cod pit this method Is noy in general use for communication in the air corps when the radio ets do not work and the annel signal will not give sufficient data air speeches act as tests for receivers it may be to listen to an uninteresting lecture but there are certain definite be derived from tuning in on one one ot the best ways to check up on the eab clency of the set Is to listen in to some speaker and note how well tha words come through do not feel satisfied tt the announcers speech comes through in good shape announcers have a radio olce to begin with they may be making an effort to speak plainly no matter how unconscious this may be tha casual speaker however gives jut a normal broadcast thus enabling tha radl olst to make an average test if the words sound mushy and in distinct the chances are that the bat teries are not up to par much of ahll Is not so often noted la picking up music many just assort t it h some new orchestral effect |