Show use of wave trap for good res results alts part Is serviceable even in in loop receiver radio expert says by JAMES H CARROLL associate Ao clatt institute of radio engineers in radio world from all quarters of tile the compass come inquiries as to wave traps rind and their uses and as to what Is the best type of 0 trap to use for good results evidently there is ie a great interest in this handy little apparatus especially under present conditions and even when the air Is eventually cleared a wave trap still will be a good ihling thin to h have ve around ar rake its as nr at example the solenoid wave trap as represented by the wim model there fire are two main reasons theo ret leally for or the success of this kind of trap and one Is because of the Noll solenoid lold Indr lg which enables the eli leal currents blowing through it ft to c ilal ilish a more evenly balanced set of lines of force which concentrate thon selves in the center of the tubing and upon the concentration point of 0 the variable condenser in tills this type of avae trap it lias atas been discovered that this makes for and has 1 a great deal to do etli tuning micrometer adjustment of interference elimination is necessary for circuits There therefore foie when using a U ft ae e trap of this variety the con denser plates will lie be pressed very slowly or the operator will not trap out the unwanted station this la Is a point in favor of tuch such a trap wave ave traps of this type can be effectively used in miny many different places if you have been unfortunate la in obtaining good results with a wave trap you may not hae used it in tile the right place in other words you may have inserted it in your aerial circuit when hen it would give you the best results 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 a and 11 1 I connect it to one of the posts on your wae 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 al aerial giai this la Is the simplest and most usual use of a wave ave trap and it Is a goodone good one but bul under certain conditions it will not prove the most ef effective reethe if by this method we do not succeed in perfectly ellmina eliminating an of offending rending station on the lower ioner waie wae lengths let us try inserting our trap in tile he ground circuit this Is done in the same way except that we substitute the ground wire for the aerial wire this menns means Is especially recommended for efficient low wave elimination but reports show that it also works equally well nell with the highest wave lengths and that also by this method additional stations have been tuned with a wave trap of of the design we are discussing now if we are working with fill 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 alo your grid wire that goes to the te tuning device in your set either coll coil or condenser disconnect tilts this wire ire at the point of contact with the grid post of the socket connect it to one end of a flexible wire about two tw o feet long iong connect another piece of flexible ible wire of the same length at tit the place ilace I 1 from which you disconnected the other wire and run these two wires outside your set to your wave trap attaching one wire aire to one post of tile trap ond and the other to the other poc post t of tile the trap you are now ready to eliminate interference tills this method even it if it is a little more troublesome to try out Is well worth while because it will make any set selective another means may be used another means we ie may use Is 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 disconnecting liec ting tile lie aerial wire to one of the pots posts of the wave trap then run another wire from tile hie ground pot of the iet bet i et to the wae nae trap although no tuning can be done one with a wave imp used in this way it functions as an excellent trapping system and stations in tile the vicinity of the set can be dominated by this means do riot not confuse a wave trap of this type with an all apparatus such as the short wave selector which Is what the name implies and not a waie trap it fills filla a very definite function of its own and curt be used very satisfactorily in conjunction with nith a trap of th the type we have selected us as the best while our testing was being done and before ihla his article was completed a letter came to hand from a fan ragn ing himself a junior radio cue bug asking for practically the information given in this text and among other things inquiring as ag to what hit became of the tra trapped loped station when then it ft was captured probably fl figuring aring that it remained Ina filed in the trap ramping ruurd and beating its it agal t tl walls in a futile effort to 0 o escape well junior you have staggered us here as we the slightest idea as to what be becomes cornes of 0 the invading station our idea Is that perhaps getting getling its nose DOC or its tall pinched in the trap it it tears rears away on the trail of other prey in the form of sets beta not protected by a beneficent wave trap the earliest form of trap ot of any kind known to history was a pit dug in the ground by the caveman in front of his cave apartment this wan aug covered by twigs branches and grasses so BO that it looked like a solid surface along came the ma mammoth in search of meat to vary hla his vegetarian diet and tumbled in with a crash that shook the row of eaves caves and dislocated every aerial in miles then all that remained for mr caveman and hla his tribe was to squat around the trap and sing and howl in chorus until they sang 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 aa it were en enclosing losina it in bakelite dis pulsing it with nith a solenoid winding and adding tin pinching condenser that squeezes the invading station until it howls for mercy |