Show edited by 0 dobilas dourly ot of radi cadlo dy by J L n it comes to bringing in tho the lations which after all are the a the world la Is better he e ordinary crystal for faithful motion clarity and naturalness e crystal has its disadvantages er cr in that it Is unstable and 0 adjust ono one must experiment nd patiently in order to find a ve spot on tile tho crystal and when much trouble a sensitive spot en found a slight accidental jar ugh gh to ret get tho crystal out of ad nt again se faults MY may pe bo remedied by how detector la Is mounted se of crystal detectors of the type that Is those that need title or no adjustment these detectors are of three general a crystal with a cat whisker bently attached or sealed scaled to a ye ve spot tw two 0 crystals pressing t each other and making cont one or more sensitive spots ectro d detectors ahlo crl real not ot crystals at all but are made chemical pastes that have the ty of rectifying rectify ing or detecting waves three types have their es in the first type tte the perma perm a connected spot slowly loses its vity and becomes in cond type the crystals become ed after a time and do not work in the electrolytic detectors the gradually dries up or Is changed i action of the current passing a it the ideal detector bously then the ideal fixed I 1 detector would be one which stay fixed when a sensitive vas as found foun d and which would nl al to be made in the the dowel sticks of the original adjustment los sensitivity after a period of use h a detector can bo be easily made ay iy y radio fan from a few simple found in every home t materials needed tire are aall all spool a crystal a small stick two small brass angles all machine screws two small with nuts 2 feet no 20 or 28 spool Is first sandpapered sand papered until it Is clean and smooth A strip of sandpaper ab about out 0 inches by I 1 inch la is then rolled into a 9 narrow tube tind pushed back and forth a few diluna through the holo hole la in tile the spool tim the sool Is then held to the lips arid and the breath blown forcefully through tile tha holo hole to expel the sawdust the dowel stick la Is now low split in half lengthwise length and a 12 inch length of no 20 26 or 28 wire vire la Is placed between tile two halves so go that about three six tent lis of till inch of the wire projects froni the end of bf the dowel stick as shown in vig fig 2 the stick Is then pushed into tile the spool hole about one fourth of tile length of tile the spool and 1 Is 19 9 then cut off flush with the end of tile the spool care should ile be taken not to break the wire in cutting off the surplus end of tho the stick A crystal Is now broen brol eri into little pieces by A heavy blow with a largo large headed hammer these pieces are tested for sensitivity by the method shown in fig 3 crystal sifted into spool the most sensitive pieces are then pulverized into it a coarse powder with the hammer care should be taken not to touch the crystal grains with the fincers since this would spread a thin film of oil over them and render them practically useless these grainy graine are scooped up with a piece of clean paper and sifted into tho the open end of the spool hole until the holo hole Is about three fourths full then another cat whisker Is made from tile alie rest of tile dowel stick and amis delm p arf y ai houft aj to test crystal another 12 inch length et df wire and nd pushed into the open end of the holm these dowel sticks should fit very tightly so that some pressure la Is ry ru quiren to force them into the eyoul liole hole otherwise somo some of the crystal groins grains may fall out tho the two small email brass angles are now attached to the ends of the spool by means of the machine screws fig 1 the detector Is then placed on the panel or base and tho holes tor for mounting it are marked and drilled fig I 1 shows how the detector Is mounted the wires leading from the cat whiskers are wound 1 around or soldered to tho the heads of the bolts and connections to tile the set tire are mado made from lugs placed between the two nuts on the ends of each bolt when all Is completed the detector may be given a really businesslike appearance pe arance by two or three goats coats of 0 shiny black enamel we to adjust the detector tap the thin part of the spool with the end of a pencil A sensitive spot will soon bo be found if after use the adjustment loses its sensitivity somewhat a few more taps wath tile the pencil will again make the crystal bring home the bacon new cw york sun and globe |