Show PAM L CIRCUIT WITH GRID LEAK resistance takes place of C battery how impedance of flow Is determined fig rig 13 snovia a set of curves for R three electrode vacuum tube circuit a grid leak resistance as shown in fig 11 instead of a 0 battery with the same symmetrical sim metrical alternating difference of potential ap piled plied to the grid circuit there being no 0 battery poten applied to the grid the grid in rig 11 Is normally at zero potential with respect to the filament As the positive half of the first cycle of the altenia alternating ting difference of potential is impressed upon the grid circuit see fig rig 13 the grid Is made positive ti m r BL A 0 a abw a GRID a 7 fa q I 1 V V V GR 0 I 1 0 FOR CHARGE on GRI IA I A WITH RESPECT Z TO REDUCTION I 1 in CURRENT MOTION of or 13 0 C ith respect to the filament being positive with respect to the filament causes a certain number of electrons electrona elec trona which are negative charges to be attracted and caused to give up their negi negative tive charges to the grid during the next or negative half of the ccle of the applied grid potential the grid Is made negative with respect to tl e filament but does not lose the elec arons again thus thus a negative charge Is built up on a grid during the post tive portion of each cycle the camu dative effect of which is to produce a decrease of the plate current during the period that the alternating differ ence of potential called a mane train is applied to the grid after the alternating difference of ot potential applied to the grid has ceased the grid does not immediately lose its negative charge the grid leak forms a high resistance path for the negative charge of the grid to leak off oft down to the filament slowly if no grid leak were used the grid NEW RADIO FILTER A MARVEL campbell device that separates tele tel phone and telegraph messages although much has been said and written about the remarkable filters employed by the telephone lines and by advanced radio workers for the ep of telephone and telegraph messages says the scientific ameri amert can it remained for dr frank 13 jewett chief engineer of the west ern electric company to demonstrate how the filter permits of transmitting radio telephone and telegraph mes sages simultaneously and of separating thee messages at the receiving end at a meeting of the american ansti tute of electrical engineers the electrical filter Is the invention of dr G A campbell a telephone engineer and makes it pos sible to separate the various frequez cies cles at which tl e individual tele phone ind telegraph messages are car ried the detected electrical current in a radio receiving set Is passed through the niter filter which separates the frequencies of the telegraph tUe graph message from those of the telephone tl TI e filter differs materially from the ordinary tuned circuits familiar to the radio enthusiast since it separates not single frequencies but bands of fre quenches quen cies of any predetermined width the filter makes it possible to sep arate the ban 1 f frequencies con n the telephone nit message sage flom fi om the bind comprising the telegraph mes sage it can also separate one tele phone message from another I 1 ground antennae r some relief from bothersome radi says strays in summertime can be ob owned with sets having blood aepli fiera fiers by using a brount antennae this Is a long insulated vole wl e ran run in a shallow trench or on the s of the ground the ground alfs should hould be run in the direction of the station from which the mosil most signals are to be receive e i and should preferably be sev eral hundred feet long to regulate wave lengths A variable condenser when properly connected in the antenna circuit may be used either to lengthen or shorten the wave length range be bides sides this the degree of regu regulation alon 1 Is much finer for at best the loading coll coil can tune in only to within a single turn it if a loading coil of tha th tang coll coil tape 4 Is used would soon collect a sufficient nega tive charge to reduce the plate cur rent to zero and the tube would ceale cease to function A grid leak having too low resist ance will not allow a sufficiently high negative charge to collect on the grid result log lag in a very small plate cur rent reduction and weak response in the telephone receivers on the tle other hand if the grid leate leak Is of too high resistance too high negative charge will collect on the grid and the condition of no grid leak will be approached in any electrical circuit that has a difference of potential applied to it the current that will ulli flow depends upon the impedance of that circuit just as in the flow of water through a pipe the quantity of water that will flow when hen any given pressure Is applied depends upon how much the flow through the pipe Is impeded by the friction of the particles of water ater against the sides of the pipe and against one another in the electrical circuit the rela tion between these three quantities Is that the current which will flow Is equal to the applied differences of potential divided by the impedance where the current Is in amperes the applied difference of potential Is in volts and the impedance in ohms on iran posing this equation the biml imbed ed ance Is equal to the applied voltage divided by the current the atice of a vacuum tube plate circuit internally between the filament and the plate when the grid Is at zero potential Is an important constant of a vacuum tube and Is called the in plate impedance the internal grid impedance of a vacuum tube used in a radio set as a detector determines the impedance of the kelepi ones that will give best results when connected in the plate circuit of that particular tube it s tl it en not only the resistance of a pair of telephones but also the in duchance duc tance and the di dl tri tributes buted capacity of the winding that cause the maxi max mum current to flow in the telephones for a given change in grid potential the internal plate impedance impe dince of a vacuum tube vanes varies only slightly with different plate voltage it is more an inherent characteristic of the tube which is determined by the design f SPARKS when our conce ts come over the wired v ireless and we plug into the lamp socket light music will be given added pop the railroads recently broad a safety message from sta tlona in pittsburgh chicago ZeN newark and mass calling attention to the fact that people have been killed or the last year in this country while trespassing on railroad property if 3 ou on do not know the code and wish to receive messages there Is a devi e on the market at the present time which records the incoming signals on a piece of paper the paper may be then read at the will of the operator this method gives the person unacquainted with rith tie tle code the privilege of hearing from stations which would otherwise pass over in the usual buzz buzz style so unintelligible to the radiophone fans while bing in the harbor of iquique aquique cl lie ile on the otest est coast of bouth america the radio operator of the steamship santa luisa clearly heard the entire broadcast program of station the distance separating new nem ark arl s station from the steamship in an air line wis 4 mlle 11 3 I 1 As a result of the widespread A interest in wireless telephony one manufacturer has brought out a set of six double faced records for teaching the tele graph code many persons at af ter listening to the radio telephone concerns have tuned in and heard tle tl e fai familiar nillar buzz buzz of the wireless wire lesi telegraph mes messages being sent cui curious lous to know the meaning of the sounds they have cast about for some means of learning the code phonograph griph records the canadian government goern govern mert Is considering the question of the amateur radio field present plans are to allow the amateur using spark a wae nane length up to meter meters while those using continuous wave transmission would be lermIt I 1 permitted ted a wae mave length up to ato rt eters |