Show edited by Q U douglas douglar NVard rop dimitor of radio the honeycomb and similar types of concentrated inductances are excellent pieces of apparatus but tho the vall able means of handling them Is crude at af the best duo due to their dimensions and shape chape especial difficulty Is 1 6 encountered when it Is desired to mount them permanently back df a marieland pa neland rieland manipulate the coupling and the inductance duc tance quantities from tho the front by means of switches and knobs A method la Is here shown where tho the colls coils ore are mounted upon a block as a unit which unit as a whole can bo be inserted or taken out of the je receiver celver cabinet by loosening two screws 1 in the bast baseboard board of tile the receiver cati cabinet 1 net ally however tile the unit with alth suf out fi clent size rolls colts for a given are left intact within the receiver here the colla coils are mounted on the block the center one permanently attached f in a vertical position with re gard eard to the holding block and securely held in place by a spring clip of brass while the two outer colts colls are ana mounted on a strip of fiber attached to the block by small hinges to permit their swinging motion at such times as the inductive relation with the center coll coil Is desired to be changed A very light pancake inductance coils easy to make experimenters will be interested in the following description of how to make a novel set act of pancake inductance colls which tire are easily construct 1 ed and do good work the colls coils can be arranged on plugs hin allar to those used on spiderweb spider salder web colls coils or connected with flexible I 1 leads ends two perfectly flat surfaces of wood or er metal for a form fonn as shown in mg elg I 1 are bound together with a bolt having two outside washers for hold fal construction of colt coil ing free ends of oil muslin anda and a spacing washer tho the thickness of the wire to be used thirty turns are wound in n pancake helix formoe fona of no ko 22 S 0 0 wire naif inch strips of oil muslin are arranged as shown in vie fig 1 2 and as wire la Is wound sticks to muslin which had previously been coated with heavy shellac when allowed to dry and remen moved cd from form tho the coll coil Is coated with shellac and again agal allowed wallowed to dry presenting a rigid article two such colls coils are used one as a pr primary lmarr in the antenna circuit with a variable condenser in series and the other secondly in the grid circuit the two colla coils when laid flat upon the table one on the other ether can be made to produce any degree of coupling by sliding horizontally later a third coll coil of similar construction st but of fewer turns la Is connected in the plato plate circuit for for regeneration era erat tion tou I 1 with 00 50 feet beet of lamp cord laid on hallway floor as an antenna in conjunction shellac ai I 1 over oil muslin fcc 7 j with a detector tube and one ona stage of amplification excellent results are obtained such colla coils can also be used an fl primary end and secondary of radio radin frequency breque ticy the ratio of turns may be made 2 to I 1 and the proper number of turns wound so as to cover any desired band of wavelength wave length ground clamps made from shade holder A pound clamp which union seizes its ita purpose very w well ell can be mado made frum from in an ordinary electric light shade holder cut olf off celoso cl osato to the 1 laner ainer circle ull of tle braces w emch ich connect the two ci Ciff lei leaving Is 4 cut cu off done dolie to the tb outer circle and then of colled collea wire tends to pull the outer colls colla downward against the cam which is quickly and easily cut cul from solid hard rubber or from sk a built buildup up form from sheet dielectric material JL 2 the cum com Is firmly attached to the shaft of 0 the knob which protrudes through the panel to tile front froat when it Is desired to change the unit of inductance it la Is not necessary to disturb b the cams came and it ts Is only be necessary to remove the hie screws which hold the block A scheme adopted in constructing a receiver employed colls coils of alx fixed ed in duchance duc tanco tance tor for a three coll receiver of the form illustrated in fig 2 the colls colis were wound in such olaes BICS that they ailt closely within eath other at least two within the alio outer coll coil tile tia same system can be adopted for the tha making of radio frequency transformers by tho the novice notice who has no data on hand for tile tho correct proportions of 0 the constants Q radio nw news hend back on itself to form it soldering lug the outer circle to Is then discarded to attach solder tho the ground CUT ON KNO HERE TO LU FIG 1 ingenious Ingen lou use uio of shade holder wire in the lug take the screw out 0 01 the clamp slip the clamp over the ground pipe insert the screws screw 11 and nd tighten be sure that the ground pipe la is thoroughly cleaned and scraped bottle neck will make good small insulator it Is if easy enough to make any quantity of small sass glass insul insulators acors tor for your leadin lead in wire at practically no cost coat at nil all in the following manner banner remove the lie necks of small vials such as vanilla or lemon extract come coma in and put lut them on a nail and fiber wa washer sher tho the latter hitter of course Is 1 used to keep the insulator from slipping lipping off the nail saturate a cotton string with kerosene ke rotene and tie it around the neck of the bottle where it la Is to be cut oft off light the string and in burning the tiring string it heats beats tho the battla neck when the fitak OR brouna STRING firo Is burned out simply plunge the bottle into cold water and then tap the bottle lightly and your insulator will fall oil right off cut neatly where you tied your string find way to obviate annoying inductance ce those of us who have hav reached the half century mark will remember when in the early days day of the telephone teje wo we used to hear several talking at the same ame time on one pair of wires in addition to this noises were hwd heard on the lines like the twittering of birds and the trying frying of eggs this was called croci croat alk it was waa a great mystery for some goma time but wilm hafi finally t traced aced by experts ts Is called inductance if you place several wires tn in a cable all well insulated and send a current of dec triciti through one of them it by some simo mysterious process eels aetis up a sort of sympathetic current in one or more of the other wires the th engineers of the telephone companies discovered several ways to counterbalance this inductance one Is by twisting the wires into pairs another to 1 to loid the ho wrea wires by adding ng sad lent inductance at mathematical points to balance that doing the inductance Is in now having its it effect upon bidlo in neighborhoods where high potential potent tul electric currents run ron ilailo engineers however claim to have found i a means of remedying th the di difficulty |