Radio Digest (Oct 1923-July 1924)

March 15, 1924 RADIO DIGEST — Illustrated Meditations by the Inventor of King Miloplex Part XXIII — Operation of Compound Wave Trap By the Mystery Man SOME time ago I was inveigled into accepting an invitation to act as valet to several Radio celebrities who were to address the Milwaukee section of the A. R. R. L., accepting after noting in particular that in payment for said valuable services the committee in charge of keeping us separated would see that w PARALLEL I "et" — or is it "ate"? — and further that said committee expected myself and those I allowed to come with me to spend only the day there. Well, far be it from me to criticize, but I am sort of up in the air as to just when night falls in Milwaukee, or whether they are not sun dodgers, because when the chauffeur in one of my yellow limousines ensconced (whatever ensconced means) me at my abode for the balance of the day, the night clerk was trying to convince a guest that he was called at eight — I use the word guest advisedly, because you know a hotel always gets the big idea balled up. How any hotel can call you a guest when you're paying six bucks for trying to sleep next to an elevator is beyond me. Maggie says, "Guest, me eye! We're customers!" and she knows. Besides, why pay a dollar an hour when billiards are only sixty cents? Economize, sleep on the pool table — oh, boy, there's a thousand ways to dodge being a guest! They tell me confidentially, though, that the only reason "Slim" Robinson at Willmette thinks so much of Maggie and so little of me is because I didn't know any better than to wipe my ten dirty little fingers on her guest towel; not that she cared so much, but the jam came when the laundry man confessed he thought the marks I left on it were a new hook-up and was trying it out on the back porch. Rawdeo is maddening — those that make your trick circuits work want to kiss you; those who don't immediately apply for a permit to carry firearms and write me asking what size hole I prefer being buried in. As one very facetious undertaker wrote to me recently calling my attention to his advertisements in the street cars, which read, "Why walk around half dead when coffins are so cheap?" Which reminds me, "it isn't the cough that carries you off, it's the coffin they carry you off in," and as you no doubt are getting going on how to use the compound wave trap we finished last week, supposin' we forget the rattle of Radio bones and dig into it. Using Compound Wave Trap You who want to use it with a crystal set will find its operation very simple, while its employment with either single or coupled circuits requires some practice in order to obtain maximum selectivity. The compound or two winding filter is used most often when it is desired to reduce many classes of interference, including spark transmitters, alternating cur WHOLESALE RADIO) Formerly at 39-41 Cortlandt St., New York City. SERVICE COMPANY 9 Church Street New York City 5 TUBE NEUTRODYNE SET Consists of: 1 7x26 Baseboard 3 Neutroformers, Columbia 2 Neutrodons 5 Nat'l Bakelite Sockets 2 Jefferson Transformers 2 Filament Control Jacks 1 Cut-Hammer Battery Switch 1 Bestone Bower Bheo and Dial 1 30 ohm Bestone Bheo and Dial 1 7x26 Drilled Panel 1 .00025 Dubilier Condenser 1 2 Neg. Leak 2 .006 Mica Condensers 8 Initialed Binding Posts Spaghetti. Wire, Blueprint and Booklet. When this set is hooked up you will be entertained by broadcasting stat,°5s ^J™3"^ ".J mile? away. You will enjoy a revelation of selectivity, volume, distance and clarity. With thecal readings ol a station recorded, ft can always be tuned in agaih to the same settings, maintaining at the same, time loud-speaking intensity and clarity ol d» «■* C% E£ft natural reproduction. «P « J \J\J Included in the set is drilled panel, ready for mounting and wiring. %J ^*== A FADA book FREE. 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Price $150; Our Price $129.50 The Radio Corporation's NEW RADI0LA III 2 TUBE SET The Radio Corporation unconditionally guarantees this two-tube set to receive from broadcasting stations Z,000 miles distant on the loud speaker. This receiver complete with Z W.D.U Tubes, Phones d»OQ 1% and "B" Batteries for only «PJ«J. I *f These sets are difficult to get, but we have a limited number, so act at once! Freed Eiseman Knockdown 5 Tube Neutrodyne Receiver Reg. Price $80; Our Price $65 Freed Eisemann Neutrodyne Kit— 3 Neutroformers and Z Neutrodons 2Z.S0 Fada Neutrodyne Kit— 3 Neutroformers and Z Neutrodons Z3.7S Columbia Neutrodyne Kit— 3 Neutroformers and 2 Neutrodons 15.50 Mail orders promptly filled and sent on all orders over $S£0. In dealing member that you are buying RETAIL AT WH C. O. D. if you wish; we pay postage | with the Wholesale Radio Service re j OLESALE PRICES luiuiiiiiiiiiiiimiiiiiiuiiiiimiiiiiiiiiiniuiiiiniiiniiiimiraiiumiiiiniiiniiffluiifliiuiiuiiiiiiiil rent electric hum, static, etc., while at the same time it permits tuning out local interfering broadcast stations in order to receive DX stations. The correct method of connecting the compound filter to your antenna and receiving set in which a series-parallel switch is used, and a method of connecting it direct to the set without the use of such a switch is clearly indicated in the two first diagrams, but I strongly urge you to use the series parallel method for its ultimate greater flexibility. Tuning In Move the contact tap switch to the first or direct to antenna tap, then, by using the tuning controls on your set, tune in the station you desire to eliminate; this accomplished, move filter switch to the opposite or last tap, which automatically inserts the primary inductance in series with your antenna. At this point all or nearly all signals should disappear and will remain absent, until by very slowly turning the condenser filter dial, they will reappear. Your filter trap is now tuned to the frequency of the undesired station, and it only remains to retune your receiver to the station desired. In retuning, particularly with regenerative sets, the tickler adjustment as well as filter condenser may require slight readjustment. The purpose of the tapped primary is but for securing varied inductive coupling. Remember always, that this device represents not only a very accurate wave meter but also a filter; therefore, when rotating its condenser dial, one will very often find the offending station on onehalf of a degree — which is advice sufficient to say, "Be yourself, take your time"; Jonah wasn't in any hurry; why rush? Give the trap a chance. Another Filter Next Week This, however, is but the beginning of compound filters, or should I say, compact compound; so, next week we will rig Up both a duolaterai and a spider trick and follow them with a loop filter that not only kisses that terrib. goodby but also does "sumfin else." Jjon't SERIES PARALLELCswiTCrtcoNNtatfi^ get the idea, though, that one wave trap will cut out three or four stations at the same time. No, son, its job is to eliminate one (any one) at a time, and the answer is, if you have two or three bothering you, then slap on a filter for each. And, as I was saying, seems to me some of my readers either don't want my picture — and Maggie's also — or methinks perhaps you didn't read the offer; hence, I repeat. All you have to do in order to get my picture and my new reflex hookup that works on a loop and uses no Radio frequency transformer is to send me a stamped, self-addressed envelope and I'll mail it to jTou "rush." (TO BE CONTINUED.) 9iy2% of All Radio Tubes Are Needlessly Destroyed Accurate estimates show that less than 9 out of every 100 tubes give their full normal service and 91 are destroyed — usually burnt out from excess current. The chances are 10-1 against you unless you use Radeco Safety Fuses These tube savers are now saving thousands of tubes. They are endorsed by the leading Radio Publications. They slip on the filament terminals of the tube and in no way interfere with the operation of the set. Price $0.50 each (The cheapest insurance) Install Radeco Safety Fuses now and whenever you buy a new tube insist on a Radeco Fuse to protect it. JOBBERS — We want a few live distributors to whom we can offer a very attractive proposition. :'iW RADIO EQUIPMENT COMPANY New England's Oldest Exclusive Radio House 20 Stuart Street BOSTON, MASS. Use the "I made Voliva whisper, then hushed him entirely!" So writes a man living t near the powerful Zion station, regard Tuning Unit »ng the use of the UNIVERSAL Its efficiency improves any circuit SILENCER Reasons Why: 1. No distributed capacity. 2. No absorption of original strength. $5.00 POSTPAID Dealers: Write for our proposition. PFANSTIEHL RADIO SERVICE "Through three or four Chicago stat! pick up Pittsburgh. Washington, D. C, and other stations at will," he continues. Why not listen to the stations you want to hear by using the Pt'anstiehl Silencer? $8.00 POSTPAID CO., Highland Park, I1L