Show I II I t u tl rU rUt t rUe e Cr i 3 Rs NI z zA A- A AMts B Tube Five TUned Radio Frequency Diagram Using Square Wound Coils and Straight LIne Frequency Condensers By CARL CARLTON iON E BUTLER Member American Institute of Electrical Electrical cal L and Institute of o Hn Radio lo Changing conditions make n w radio circuits necessary A few years ago the single circuit and ultra uHra receivers s were wert satisfactory slid were capable of bringing In cuts dis- distant dis distant tant tent stations with volume today the seine same sets cannot be u used e except In him Isolated districts away awry from broad broad- broadcasting broadcasting casting stations due to their broad tuning qualities The receiver of ot the earlier day is 13 lano no longer satisfactory for other rea rea- reasons reasons sons principally on account of ot IL Its squealing and radiating qualities and because Its tone quality is poor and distorted At the last radio confer confer- conference conference conference ence In Washington It was agreed tint that tintin In the tho near future the use of or radiating receivers would have to be ended even een e c en enIt It if It became me necessary necessary to pass a n fed fed- federal federal eral law to accomplish that result Today Tony with modern laboratory standard apparatus available and andI I I with sets of ot better design n the quality attains the standard demanded by I lovers of ot music I The 4 n circuit as developed for use In n a new receiving set is n a good example of ot present day design The most popular form torm of ot circuit was the selected the five fi tube tuned radio frequency and by the use of ot the lat lat- latest lat latest est type of or condensers coils colls and transformers together tog with Improve Improve- Improvements Improve ments in the the circuit produced n a re- re receiver re receiver that Is capable of ot tuning through h Interference bringing in sta sta- stations stations inns from a distance on the loud loudspeaker loudspeaker speaker ker and surpassing man many reo re- receivers re receivers for tor all e and quality of ot toneTo tone To Shut Out Stray Currents Noteworthy of ot the improvements In Inthe the circuit are two pass bypass by pass fixed con con- condensers condensers condensers between the flue primary of ot each of the first two radio frequency trans transformers transformers formers formers- and the filament This Thus serves sef s to pass by-pass antI and keep stray radio fre frequency free fre- fret quency currents out of ot the rest of the t wirIng and stabilizes the lie circuit A large condenser Is placed across Deross the tim e n B batter battery terminals to reduce noises noise s and howls ls due to long leads or low to w Refinements In apparatus Include e the new square squar wound coil coli wIth the new straight line frequency condensers which provide which which- provide shielding shielding- ot o electromagnetic lines pt force torce as well ns as keep the instrument a mighty Important detail I IThe The Time coils colls eliminate the spraying effect elret of ot magnetic lines of o f I force torce within the set proper and re- re remove remove re remove move the principal bugbear r that radio engineers have vl been working for years to solve e The coils colls have sel self con tatted fields that make pickup of ot stray current Impossible Their use In 4 time the n 4 receiver makes a set sot that will tune through stron strong Interference The variable condensers on the lie first and seco second HI stages of or radio may be tuned by one control as ns In the receiver If desired Three condensers mind t three dials may he be used In the ordinary manner how how- however however ever without les lessening The Parts Needed To construct the lie circuit you will need the following pacts 1 Square wound torpid coil coll type Tl Ti indicated on diagram as ns LI Lt 2 Square Squar wound oIls coils type r Indicated ted as ns 12 mind 1 13 3 Straight line frequency variable condensers preferably the Ameri All can shielded type Indicated on diagram as ns Cl and 2 Rutland lyric audio transform transform- transformers ers type 3 OO fixed d condensers In- In In Indicated d on diagram ns I C-I C Cn Ci arid and CS 1 n fi fixed 11 condenser In- In IndIcated indicated In Indicated on diagram as H CO Crt 1 10 mid fixed condenser In In- In Indicated d on diagram as InI I The 1110 rheostats rheostat should each be ot of six ohms capacity for the time use uco of UV Ol-A Ol A A or C A A tubes and the lie grid leak should bo he two tO o oms ms the new UX U amplifier l tunes I break the lie grid grill return of or the lie last mud mill Insert C battery of If I recommended b by the tact Time The first rheostat t Is used ns as n a volume control to moderato moderate signal strength to the desired extent For Formost Formost roost most satisfactory operation the lie cor- cor correct cor correct selling Betting of this Ills control may many he determined by trial mill amid then lien allowed to remain without Jt further adjust adjust- adjustment adjustment ment In Jim addition to the apparatus named II above bove you ou will need five e sockets a 7 1 by Inch 24 panel ba baseboard or sub sub panel panel punI wire screws solder et etc to the set gEt The terminals of ot the radio radio-fre f Cuen quency fre-quency Inthe transformers are arc unmarked In n the diagram The rhe first coil coll Is a coupler vt with Ith two taps token taken ot orr far tor 1011 l ong and aull short aerials Both noth taps are marked A and each should be tried and time the aerial connected to the one that gives gins the best hest Ie results The other two t wo taps arc are the secondary cornet lIon tiers connections SIr and r rr f kr d v in the lie regular wa way The outside terminals or If the second and third tIdd coils colls are time the primary posts the Inside terminals being the 0 and noll F secondary term terminals Innis Three Circuit Is B Best st Wave Short-Wave Radio Set Sel SelAn An easy wave short set to build Is Isone Isone one on the order of ot the t set The tuner for this set Is made from any good three-circuit three tuner about I 4 Inches in diameter The secondary consists of ot ten turns of ot No 12 wire the primary of ot four turns of ot the same size wire the two being medium coupled The Tile tickler has 20 O turM ot of No 20 wire The secondary is tuned with a n condenser as shown by the I w rose y Diagram Showing Circuit of the Short Wave Set sketch Another nother Important point t to note is In winding the tickler To ob ob- 0 obtain tain tamn the best results care should b be betaken taken to see that lint all turns are wound d In the same direction and an even eve number of ot turns on each side of ot the th e shaft This set will receive approximate from 2000 to kilocycles cles or from frog 40 to meters However every set se seis t Is different and In order to check you r maximum and minimum wae was tt e e length s you ou should obtain Information from fro m mo time the standard frequency station as to t tI o when hc they send test programs an I with these signals you will wll be he able to t 0 tell exactly what wavelength wave your our se sewill set will cover er In assembling a short short wave wave receive t keep in mind the lie fact that all lead should be just as short as you ou can ca camake n make them If It you can get the or assistance of ot one of ot the many ama ama- amateurs amateurs curs who have ha successfully built a wave wave short receiver it will be of ot grat grey t Philadelphia assistance Philadelphia Record |