Show edited by 0 dougl koltor of 0 bablo MM I 1 J 1 cat j JL P 1 ast T orf W t f ti 8 V r A I 1 3 i SET WAVE tv this Is a wave wava trap trao that works such a trap la Is being asod by one of th tho government receiving stations Sta tlona which operates on meters and upward less than a mile from a meter broadcasting station at the present time there Is no practical solution for every interference problem that a radio fan may amy have however there ore are a great many cases of interference that can be solved by the use of a properly construct edware trap it Is the purpose of this article to give the results of tests which have been made and to explain exactly the construction i of a trap which the writer believes bel leves will be of much help to many of the fans just such a trap Is being used by one of the government receiving stations which operates on meters and upward nod and Is less than a mlle alls from one of the largo large meter broadcasting stations defore before the trap was put into service signals from tile the broadcasting station could not be tuned out regardless of how the government receiving set was tuned in iii fact the interfering concerts could be heard for many feet fro from in the phones pl iones before the broadcasting station was finally allowed to begin regular operations the problem of interference had to be solved soloed several traps raps were made find tried out and finally one was developed which cleared the ilia trouble conditions were Illo rigorous orous the conditions which the trap had to meet were very rigorous when the broadcasting station was in operation it was necessary that it should not be heard la in the least when the government set was tuned to meters or more for tills this test tile the receiving set was tuned to meters the lowest wave length used in the reception of messages at that particular station also iso tile the regeneration was set at a minimum I 1 and two amplifier tubes lu ili addition to the detector were employed the fact that no regeneration was used made the receiving set much less selective even though it was a loose coupled type also it was required that the uso use of the trap would not noticeably cut the signal strength of any messages that the operator desired to receive Fin finally nIly after bull building dIng several traps using various sizes of wire inductance and capacitance an arrangement was found which met the speckled conditions it was possible to tune time the receiving set as low as meters before the meter broadcasting signals were audible there was no noticeable change in intensity of meter stations when the trap was cut in and out of circuit when the receiving set was adjusted to meters about IDO 00 per cent of the interfering signals was eliminated tho the accompanying diagram illustrates how the trop trap should be connected in circuit when tho the condenser Is adjusted so that the circuit resonates at meters for or example the trap offers theoretically on infinite impedance to any incoming signal of the same edme wave length in actual practice the impedance of the trap nt at resonance Is not infinite due to the fact that a loll 1011 cannot be made which has bits no resistance si but it Is however very high all other signals above or below meters find their way into the receiving set since the trap Is not in resonance with them how inductance Is made the inductance Is made by winding 17 turns of no 15 or vo 1 0 o ig 10 D 0 0 copper coppe r wire on a 41 bakelite tube the var variable labia condenser Is mad or the usual 43 plate type the fixed condensers are niso also mcd of mica dielectric two single ringle polo pole switches make it possible to cut in or out the fixed condensers in order that broader range ot of tuning may be had find on tile trap the other single pole switch makes it possible to cut in or out the wave trap as desired after tile proper capacity has been determined for any particular receiving station it Is probable that switches will bo be unnecessary for cutting tho ilia condensers in and out of circuit the trap will cut out meter stations when one fixed condenser Is in circuit and the variable condenser Is placed approximately at mid setting to eliminate higher waves increase the condenser capacity and for shorter waves decrease it cutting in or out the fixed condensers its as necess necessary tiry if a n loose coupler or varlo coupler arrangement Is used in the rec receiving elvIng set very close coupling must ile he employed otherwise the trap will not bo be at till nil effective the trap will slightly filter alter the pre previous ilous settings of the receiving set but not to an appreciable extent this particular apparatus will undoubtedly bp of most service in eliminating meter stations when one desires to hear fiM meter stations and vice versa those who have trouble from commercial spark sets will also find it a great to a radio set |