Evening Star Newspaper, May 19, 1922, Page 24

“Expert Advice on Radio 5.—Working of Crystal Detectors. BY A. HYATT VERRILL, | Expert on Radio Technology. Crystal detectors are perhaps the most important part of tane érystal receiving set, for without them it would be impossible to hear the sig- nals and messages, even tnough they came to the set through the aerial and the tuning device. Although a crystal detector is a most simple af- fair which any one may build in a few minutes, yet it possesses really remarkable properties. The purpose of the detector is to cut the oscillat- ing or alternating currents in half, in this way acting like :ivah'c and permitting the waves to flow through in one direction, but not in the oth- er. This is e: for otherwise frequenc owing to the fact that the human ear cannot detcet vibrations of more than 10,000 per second. The portion of the de- tector which hes this r as a valve is 1. A great s, such as car- pyrites and galena, rity of allowing a current ¢ ‘to pass in one direction. but not in the other. and the same results may be ed by means of nitric a platinum wire, but as galen; most sensitive known sub which acts in this way it is the mate- rial usually employed for the pur- pose. peculi Galena Is Lead Ore. or “crystal, it is com- led, is not, as man manufactured article . but the natu lead - ore »wn technically as lead sulphide, or. in other words, a combination of lead and sulphur. It is the common- most widely used lead ore aries gre. composition. Most galena is ation variable in its proportions of lead, sulphur and other metals. is never uniform. even when obtained from the same mine or same vein. and its sensitiveness to electrical currents varies with its purity and its composition As a r sult it is impossible to secure two piecos of galena exactly alike, and! obtained by} Eood re: testing a n tector and ting those which give the best resu ts. Indeed, so greatly ary tha ne smail piece there are s which are not are highl son dete portion L hed by th wire contact known G ker.” B. Figure 1 ordinary form of dete sists of a crystal or holder, Figure 1 C, a movable upright, D, an arm or and the cat whirker or con- o The w are connected to binding posts. F F. the wire from the aerial and tuner being connected to one and the phones. while the oth- er ground wire. Omne o fthese binding Pos¥ is led to the upright carrying the cat whisker, while the other lea to the crystal cup. Then. when the set is to be used. the phone receiv. I H l | I iresults are never twice alike. is adjusted and the cat whisker is moved about over the crystsl until the most sensitive spot is found and the crystals come ciear and loud. A Shmple Detector. But a detectsr Which will work mi be made much simpler, for all that is necessary is some sort of ® og & nection between the wires and the cat whisker on one side and the wires and the crystal on the other, and a small coiied. wire supported by a bit of brass and a clip or clamp holding_a wire to the crystal will werve. However, such makeshifts are nver satisfactory, for the efficiéncy of a detector depends largely uppn the variety of motions which may be obtained by means of the adjustable apm_carrying the’ cat whisker and the upright which holds it Moreover, the affair must be rigid and a perfect contact must be made between the crystal and wires. In order to accomplish this the crystal is often mounted in the cup by means of fusible metal or a composition of mercury and tin, but a r _better method is to wrap the lower part of the crystal in tinfoil and then clamp it in the cup, if necessary, packing bits of tinfoil in the spaces between the cup and crystal. The arm which holds the cat whisker should be pro- vided with an insulated tip or knob to prevent one's fingers from carry- ing off a portion of the electrical cur- rents and to avold the necesity of touching or handling the cryatal: the cup should also be adjustable to vi rious positions. If a crystal is touched with the fingers it will soon lose its sensitiveness, owing to the grease from the skin. This may be removed and the sensitiveness restored by washing in alcohol or ether. But even the best crystal detectors have their faults and their limitations. In the first place, considerable time and trouble myst be used in adjust- ing the contacts and, even when this done, the contact may be altered or broken by the slightest jar or vi- bration. This adjusting must be done usually each time the Set is used, and s it next to impossible to find the exact spot on the crystal twice the More. over, a crystal detector set is very limited in the distance at which it can recelve music and messages, the utmost range or distance under or: dinary conditions being about twenty- five miles, although Joud spark sig- nals,may’ be heard for many times that distance. A Faults of Crystal Set. Another fault which many persons unfamiliar with radlo do not realize and which causes much disappoint- ment Is that a crystal set cannot be satisfactorily amplified or its sound sagnified so that the sounds coming through it are audible without using head telephone receivers. . Although by attaching a megaphone or phonograph horn to the receivers the sounds may be increased some- what. they cannot be bullt up until they may be heard all over a room or all But. despite all this. thousands of crystal sets are in daily use and are giving immense satisfaction and in- calculable pleasure and enjoyment to their users. If near a broadcasting station they give good reception and, as they are very simple, cheap and require no bat- teries, they will always be favorites with ‘many people.. Moreover, they are the best sets for beginners, as with them one may learn the first prineiples of radio telephony, while any one with the least mechanical ability may make a set which will do as good work as any ready-made set costing several times as much. (Copyright, 1922. (Tombrrow- ‘Operation of Head Phones.”) _— European rovalty as a rule h: ways shunned May weddings. al- The is connected to the phones and|one notable exception in recent years was that of the King of Spain and Princess Ena of Battenberg, and the royal bride and bridegroom narrowly escaped being blown to pieces by & bomb while returning from the ers are placed over the cars, the tuner ceremony. LANSBURGH € BROTHER BRING YOUR RADIO PROBLEMS ToO vs Boys! Our New RADIO Dept. Is Open All parts, diagrams and supplies for building your own set, from the simplest to the most elaborate receiv- ing hook-up in stock. A Large Supply of DETECTOR BULBS on Hand Radio Dept—Fourth Floor. Of the Same Material. [—ac e TOR WHITE FLANNELS 4]- TAILORED TO YOUR® MEASURE—tai- lored to fit perfectly and from all-wool blue serge. Your coat will be tried 6n in the baste and made right here in Washington. IF YOU CHOOSE WHITE FLAN- NELS FOR THE EXTRA PAIR OF TROUSERS, you can have either plain white or’striped. 0 vou THiNk Tis SPIRAL AR-WIRE. WiLL WORK, RALF ? BY RADIO TODAY ; NAA—Naval Radio Statton, Radle, Va. 10:30 &.m~—Meteorological report on 5,950 meters of arc transmitter. 12 noon and 10 p.m.—Time signal, followed by weather report and ship orders. 10:30 p.m.—Naval press news. Wave length, 2,650 meters. WWX—Post Office Department. 10 a.m—Weather report for the District of Columbia, Pennsylvania, Ohlo, Maryland, Virginia and West Virginia. 10:30 a.m.—Marketgram (fruit and|’ vegetables) on 1,100 meters. 12:30, 2:16 and 3:30 pm—C. W. marketgram telegrams on 1,980 me- ters. 5 p.m.—Wholesale dairy 1,160 meters by radiophone. 7:30 and 83 p.m.—Market report on D meters by radiophone. 0 p.i ‘Weath report. Eleetric Com- meters). 0 p.m.—Base ball scores “Blue Bird Land” (Short); report on tenor tide,” piano (Huerter); trot (Clift Friend, Wright “Polonaise,” piano (Chopin Two, Three, Four” Sprites,” plano Glovanni, (Mozart): baritone “Pick Me Up ahd Law Me Down"” (Kalmer-Ruby); “California™ (Friend-Conrad); “Springtime,” plano (Brandeis); “All That I Need Is You" Saer “Poor Carnation (Anon.); “Those Songs My Mother Used to Sing,” piano (Smith); base ball scores announced. NOF—Navhl Alr_Stition, Amacostia (412 Meters). Z 8:30 to 9 p.m.—Program of music Radio Institute (360 Meters). 6:30 to 7 p.m.—Radio spark code. WPM—Thomas J. Willlams, Inc. (368 eters). 12:30 p.m.—News items; stolen automobiles. 3YN—National reports on S. A. WVP—Signal - Corpa, T Meters). HEY. CHALKY! LET GO THAT PALE AN’ HELD ME GET THIS RADIO. UP! A UNIQUE TWIN RHEOSTAT. Many radio experimenters are endeavoring to build small portable radio receivers which can be carried to camp this summer. The cabinets must of necessity bhe as small as possible in many cases. . This means that the parts used must allow of Apace economy. i WGY—General Electile Compuny, Schenectady, N. Y. (360 Meters— Eastern Standard Time). 12:30 p.m.—Stock quotations. tock quotations; base ball 5 p.m.—Program of music, KYW—Westinghouse, Chicago (360 Meters — Central _ Daylight-Saving Time—Same—as Eastern Standard Time). | 9:25 am.—Opening market quota- tions, Chicago Board of Trade. 10 a.m.—Market quotations at one- half hour intervals until 1 p.m. 1:20 p.m.—Closing market quota- tions 2115 pan.—News and market reports. 3 pm—American and National League base ball team line-ups; pro- Bress of games every half hour there- after until their close. 4:15 p.m.—News, final financial reports. | "6:30 p.m—New. returns. p.m.—Children’s bedtime story. l 8 to 9 p.m.—Program of musi 9 pm.—News and sports. market and final market and New Apparatus and Devices By Ralph Brown, Radio Engineersaaaaan o The twin rheostat {llustrated re- quires a circular space only one and five-eighths inches in diameter on the back of a panel and extends only oneé and one-half Inches in depth. As may be meen, the coiled resistance wire is. mounted on two grooved cir- cular disks. There are thus two resistance coils, one end of each béing connected to the binding screws. The contactof slides over both colls at the same time when moved by the knob, 50 that the circuit is from one connecting screw through some re- sistance of one coil, through the contactor to the resistance wire of the other coll and to the other bind- ing screw. The current is not con- ducted through a bearing. This is a distinct departure from the cus- tomary design. It is claimed that the use of thia rheostat gives great freedom from noises due to imperfect contacts. It appears that the claim is well found- e The total resistance of the rhéostat is five ohms and the “off” position is at the end of maximum tance. ' A R e i e SRR R VS | S T A e WWJ—Detréit News (Eastern Stand- ard Time). 9:30 a.m.—Houséhold hints to house- wives; musio (360 meters). am.—Weather report (485 2 m.—United Statés Naval Ob- servatory time signals (380 meters). 12:05 p.m.—Music (360 meters). 0 p.m.—Market quotations (485 (485 mexr«x 405 p.m.—Weather port results and meters). 5 p.m.—Complete world news (485 meters). p.m—Program of music by Josk- phine Murray, soprano; Charles O. Wra; bags; Grinnell Brothers Cho Jonie ‘Quartet; the Steinway our. report WJIZ—Weatinghouse, Newark, N. J. (360 Meters—Kastern Daylight Sav- i85 Time—Deduct Ome Hour). 8. a.m.—Agricultural reports prices as released by New York, Jersey and federal bureau: 10 a.m.—Program of music. 11 a.m —Program of musgic. Noon—Agricultural report: er forecast; program of music. 1 p.m.—Weather forecast: program weath- £:50 p.m.—Instruction in radio. rogram of music. Meri all agree that these Five Dollar shoes Hit the Bull's-Eye! y And therc's No “Bull” about that! For the way men are and asking for them— And eagerly buying 2 and 3 pairs at a clip— Shows there's a lot of talking going on around town abeut these 35 Shoes. . We sute did start’ something big when we made up our. minds to put out the biggest . Five Dollars’ Worth of Men's Shoes seen in years! On Sale at all our stores, including the “City Club Shop” “City Club Shos" \I318G Included in this great $5 line: Brogiies, sémi - brogues— square toe lasts—modified English—and conservatives. Shoés or Oxfords. Scotch Grains—Norwegian Calfs—Patent Colts — tan ~and black calf—and smoked elk leathers. All Goodyear Welts—and all real shoes! - Cor. 7th & K 414 9th Se. 1914-16 Pa. Ave. St 933PaAve.SE. 2 p.m.—Shipping news; program of music. 3 p.m—Basé ball scores; program of music. 4 p.m.—Base ball scores; program of musdlc. W] p.m.—Base ball scores; program of music 8 p.m.—Weather forecast; agricul- tural reporis; program of music. 7 p.m.—"“Man in the Moon" Stories (c) Newark Sunday Call. 7:30 p.m.—"“Athletics,” by William agarty, - past president of the escent Athletic Club of Brookly: 7:45 p.m.—"Colors and Their Use: by Martha J. Phillips & 7:66 p.! “The Trend of Business by the Magazine of Wall Street 8 to 10:15 p.m.—Concert arranged by the New York Conn Company. 8 p.m.—Eddie Elkins’ Orchestra, now playing at the Pavillion Royal, Valley Stream, L. 8:15 p.m.—John cornet soloist. 8:25 p.m.—Ralph Corey, trombone soloist, Mark Strand Theater Sym- phony Orchesrta. 3:35 p.m.—Kitty McLaughlin, prom- inent vocall 8:45 p m.—Miss Madeleine MacGui- gan, premier violin soloist. 8:55 p.m.—Ralph- Corey and John Dolan, trombone and cornet duet. 9 to 10 p.m.—Mark Strand Sym- phony Orchestra, comprising forty- seven artists, Carl Edouarde con- ductor. [ow to Choose and Get a Better Job,” by Prof. Edward Jones Kilduff, School of Commerce, New York Uni- versity; courtesy of Harper & Bros. 10:62 to 11 p.m.—Arlington time signals. 11:01 p.m.—Weather forecast. I Dolan, prominent WBZ—Westinghouse, Springeld, Mass. (360 Meters—Eastern Day- light Savim lwet Ome Heur). 8 p.m.—Base ball scores; program of music by Alpaulmil Trio, with Alberta Kelleher, violin; Pauline Kellelfer, piano, and Mildred Kelleher, cello. KDKA—Wehti: cvera T 1N (380 iele?l—'.‘.;.:!lrn ;:n"r: m.—Music, m. to noon—Music. 2:30 p.m.—Results of all | ball games by innings. ase ball scores; theatrical gue base p.m.- features. 7 p.m.—"The Draftsman Work.” by of drafting of Carnegie Institute, Pittsburgh; “Insect Pests and Disease i ! ! and His|of Vegetables,” by C. C. Leeds of the school | extension i CAPACITIVELY COUPLED RE- CEIVING SET. Capacitive coupling is sometimes referred to as ‘“electrostatic” ¢ou- pling and is secured by coupling two circuits with one or two condensers. The method of using two condensers 15 lllustrated in the figure, and both may be arranged so that their capa- city is controlled by one knob. Some- times both are mounted so that their movable plates are carried on the same shaft, each set of plates being insulated from each other. When capacitive coupling is used it is ad- visable to either remove the induct- ance coils to some distance from each other or to_place them at right-angles. When this is done there is very little inductive coupling. When a difference in potential exjsts between the opposed conduct- ing surfaces of & condenser—that is, when a voltage is applied to the con- den; the dielectric is strained. It is quite impossible to see the effect in the dielectric. but the effect of too great a strain appears as a rupture W. D. Benedict representative of the Al county farm bureau. variety of musical selec. legheny 8 p.m.—. of the material in the case of a solid dielectric. k_would then pass through the hole and the condenser would be “punctured.” dent may easily happen in a tran mitting set under certain conditio but rarely if ever occurs in & recei ing condenser. The point is how- ever, that when there is & strain in the Qielectric material there is some energy stored in the condenser which may be given up on discharge. The straining effect acts in a certain di- rection, from the positively charged plates to those negatively charged It is customary to imagine the pres- ence of lines of force, since when the force is greatest the charge is great- est, and the lines could then be con- sidered as being closer together. The imaginary lines of this electrostatic force constityte the electrot tie fleld through which energy may be transferred—in our case of capacitive coupling from one circuit to another The degree of coupling is controlled by varying the capacity of the two condensers. Large capacity Eives close coupling and small capacity loose coupling. To a great extent the wave length of the antenna and se- condary circuits can be altered with- out varying the coupling, it being de- termined principally by the coupling capacity, as stated above tions by Miss Lillie E. Steber. colora- ture soprano, and Phyllis Geraldine Gray. pianist. 9:55 p.m.—Arlington time signals ---that will suit you ! OU can take that literally—the price will suit you, and the suit will suit you. And it’s the latter part that is the key of the whole story. For it's what you get for what you pay that decides value! From sport suits to conservatives— everything! Wonderful blue serges, hard worsteds, tweeds—everything! Doing very well with this newest Fashion Shop suit proposition, thank you. And why not? Was Washington ever slow to recognize something worth while? An established feature with us GOODMAN & SUSS CLOTHES 15th &G Tailored at Rochester 93-point Hand-Tailored FRED PELZMAN, 3 GOODMAN & SUSS Cm‘ TAILORED AT ROGHESTER MANHATTAN SHIRTS t i : flmg STETSON HATS—INTERWOVEN SOCKS Tastion Ghop 9th & e,