Show W edited by G editor of radio E by J L L crystals are tast fast becoming unpopular as detectors and rectifiers of radio waves except for its use in reflex circuits the crystal Is now used only by those who cannot afford the more expensive vacuum tuber tube the main reason for the neglect of the crystal Is the fact that crystals have a limited receiving range except under very favorable conditions another reason for the unpopularity of the crystal Is in that most crystal circuits do not provide sufficient selectivity and the different broadcasting stations interfere with each other in the set were it not for these two crystals would be even more widely used than vacuum tubes for radio reception in the first place cry crystule stuls are very much cheaper to buy and to replace than tubes secondly showing how rotor Is mounted upon stator tube the crystal does nut not require any batteries to run it as tubes do and thus thua has no cost of upkeep thirdly it la Is a well known fact that crystals cry stala give much better and clearer reproduction of broadcast speech or music than vacuum tubes do an exceptionally eff efficient lelent crystal set can be built it if the directions and diagrams given are carefully followed this set will give surprisingly good results and will cover far greater distances if properly tuned than the ordinary crystal set the parts needed to build this re k celver are very few and if the Is made at home according to the directions given the cost of the bet not including aerial ground and pl phones iones would be small parts needed to build set the materials needed are one varl varlo occupier coupler as described one 23 plate mad condenser one crystal detector one mad fixed condenser one panel 7 inches by 10 inches one baseboard 0 by 0 9 inches aerial ground phones the varlo coupler may be any one of the standard makes now on the market or it may be constructed in this way get a cardboard or composition tube about 3 inches in diameter and 0 6 inches long an empty oatmeal or salt box will do very nicely one inch down from the top of the box punch two small holes one quarter of an inch apart procure a spool of no 20 or 22 double cotton covered wire and weave tile the end of the wire back and forth through the two holes until t wire Is firmly anchored A few inches of the end of the wire should be left free to make connections to now the winding Is begun wind ten turns of the wire as closely and tightly as possible when the tenth turn Is wound hold the turns securely 40 a 3 A diagram showing Fosi position tion of the various instruments with the left hand while you twist a little loop in the wire with the right hand this forms forma a tap wind on eighty more turns with a top tap at the end of every tenth turn do not make the taps directly under each other but a little staggered to one side as shown in fig 1 these form the tens taps nine more turns are then wound on with a tap at the end of 0 each turn tum these are the units taps after the ninth turn has been tapped wind another turn tum and fasten the wire securely by means of two small holes as in the beginning of th the e winding leave I eave a few inches of wire sit at the end to make connections to Mounting the rotor now Nw get a wooden rotor ball about three inches in diameter this abis rotor bell ball with brus brass fit fittings tInge for mounting it upon the stator tube can be obtained at any radio shop sixty turns turna of no 20 wire are I 1 wound upon the rotor about two inches of wire being left at vach end of the wire for connections the rotor la is then mounted courted upon the stator tube as shown in fig L 1 two small holes are made in the stator tube directly opposite each other and one half inch down from the top of the tube the mountings for the rotor ball are pushed through these holes stranded wire la Is used to connect the ends of the rotor winding to two binding posts at the top of the stator tube this ills completes the varlo coupler A thin coat of or of shellac diluted with alcohol may be over the winding to keep the turns turna in place the taps are scraped tree free of insulation so thi th t the leads from the switches may be soldered to them the parts are am now mounted upon the panel and baseboard the position of the various instruments la Is shown in figure 2 the varlo coupler to Is mounted on the left the switches leading to the tens taps and the units taps respectively are in the center and the condenser Is mounted on the right this makes a very neat and simple panel layout the crystal la Is mounted above the switches it if a fixed fired crystal detector to Is used it may he be mounted inside the set and will relieve the operator from the necessity of making delicate crystal adjustments wiring la Is simple matter the te wiring diagram shown shawn in fig 3 ar 1 very simple and easy to follow tle the aerial a single wire about feet long Is connected to a binding post in the upper lefthand left hand corner of the panel the binding post Is in turn connected to the stator plates of the vt triable vur lable condenser the ground a connected to ro the nearest radiator or cold water pipe Is connected to another binding post on the lie lower lefthand left hand corner of the panel tile ground binding post la Is connected to the units switch and to one end of t Y 7 bens e ns V 7 14 wiring diagram very simple and easy to follow the rotor winding tile the movable plates of the variable condenser are then connected to the tens switch and to the eat cat whisker of the crystal detector the other end of the detector and the other end of the rotor winding go to other binding posts on the panel to which the phones are connected the fixed condenser la is connected across the phone binding posts use bus bar or no 14 copper wira for making connections and solder all the joints well before soldering the leads to the rotor windings try reversing the connections that Is try changing around the lends leads going to the two rotor binding posts tuning this set Is very simple and does not need any description the crystal la Is adjusted and the dials and switches are turned aunill the station to Is picked up after which final adjustments are made to bring in the station na as loudly as possible and to eliminate interference from other stations |