Show ed ted by 0 doug as editor of radio merchandising J S here Is a stunt for Us ng one for two stages of tuned im fedance radio frequency amplis cat on there are only two prin A IL cipal controls by A L MUNZIG I 1 would like to present a novel means for tuned impedance lm control for radio frequency amplification tuned impedance offers twice the t tion that transformer coupled types I 1 can give so why not usa use it f obtain a standard make of varl ometer and take it completely apart ditl out disturbing the molded windings separate the two stator wind mind ings and the two tuo halves of the rotor winding bring out leads through small holes drilled in the rotor form assemble and connect one side of the stator winding in series with the cor responding halt half of the rotor do the same with the remaining stator and rotor halves thus we have two vario varlo meters in one that change their tl mutual inductance s cheapest and simplest regenerative receiver the novice Is always on the look out for a simple and cheap receiving set which Is efficient in operation here Is what Is believed to be the best in this respect ever described for the receiver the folio fol loving ving parts are re quiren one varl ometer one 23 plate variable condenser with vernier one 1 inch switch lever two contact points the usual vacuum tube and its accessories fill the rest of the bill with the usual amateur antenna this receiver will easily respond to trans bitters operating on wave lengths from I 1 U f 4 2 81 by breaking the connection from rotor to stator any can j be adjusted to this C rout acu t the rotor co I 1 functions as the tickler up to and including meters the accompanying sketch explains I 1 ow it Is done first single connections are brought out from the two outside windings of the vano vari moter so that they lan an be brought out to the two contact points the rhe leads from the inside or rotor coil of tl e are connected in the plate circuit of the vacuum tube thus converting it into a tickler coil Rgene Regene raon Is controlled in the usual manner by ad the rotor col for reception on the lower wave lengths the switch arm la is placed on the i point marked I 1 and on contact point 2 for the higher waves this is a good stunt and well worth morth trying radio news 1 antenna wire A one wire antenna will mill be suitable for use for receiving string the wire as high as possible and away amay from ob point the antenna in th direction that you wish to receive from for the most efficient results the end of the antenna at which the lead Is bought to the set la is the pointer and should be directed at the tra transmitting station that 3 ou would wish to listen to most regularly thereby doing am a ay with an extra con arol allowing two stages of radio fre quency to be available minus several critical adjustments by shunting a small fixed condenser across r 0 ss each they must be of the same capacity they can be made to function as radio frequency tuned impedance transformers on amateur and broadcast wave lengths the value of the capacity used de on tl ti e waves wanes to be covered some of the readers may be dubious about the practicability of th s stunt due to the fact that both tuned im penances pe dances are in too close proximity to each other however this is an ad vantage and not a detriment to tl e efficient operation of tl e amplifier connections for two of tuned radio frequency ampi fl fi cation ara ar shown in rig I 1 radio new nem s place to get wire to construct your loop the radio fan with limited means who desires a loop aerial Is sometimes up against it because of the high price of such apparatus still as long as necessity Is the mother af f invention and as long as we me I 1 an e scrap heaps the fan can at least rig up a tute for that which he desires expensive stranded or ribbon wire Is desirable for use on a loop and if the experimenter will go to a garage he can get an old magneto field coll coil for little or nothing oh this field Is wound about inches of copper rib bon wire one fourth inch wide in 16 foot lengths this kind of m wire ire is said to be far superior perlor bu to ordinary wire for aerial purposes owing to the in creased ed surface it ches to the flow of the radio frequency currents ribbon wire may also be used to shield panels connect up bour our set and short pieces may be used as connect ing links or battery connectors therefore a roll of it should prove a valuable addition to the radio axim menters menter s hope chest how to lengthen life of your B batteries the amount of service you will ob tain from a B battery depends to a great extent on the care you give it the foll following oming pointers wilt will assist in securing the maximum number of hours of useful life from the battery do not subject your B battery to high temperatures handle it carefully lou may ruin your B battery by dropping it on the floor as this may break some of the internal con nc sections tons do not short circuit your battery even momentarily A short circuit of only a few moments duration will drain a considerable proportion of the total energy out of the B battery foy for this reason if you wish to test the battery use a high grade voltmeter and never an ammeter N voltmeters olt meters are high resistance instruments and give a good indication of the condl alon of the battery wit mit out drawing excessive currents from it ammeters are low resistance instruments and when placed across the terminals of the battery practically short circuit it insulating leads the insulation of the leads in a radio set get Is very important where lea Is 1 cross one another though not reil rell close it Is best to slip a few inches of spaghetti or some other insulating mi tall aerial across them do not run any leads parallel for any length SYMBOLS USED IN RADIO PRACTICE o 0 0 C bof 1 OF WU VV RE AMTER NO TRAM aae WENNA ANTENNA Y COUPLED COU vacuum tim 4 ARC X DATTER nw DETECTOR 1 C buzzer aa 1011 CONDENSER fum RES 9 VA 1 pvc valuable CONDENSER 1 1 W QUENCHED hillh efu GROUND A SWITCH MH X PCT PDT i 1 TELEPHONE A at IRME VEX aar AR mft tt L pal A I 1 n bj |