| OCR Text |
Show t 1 1 lrl 0O0tf3Ory Output U t I Jack I 1 I AfW ? ! X J 1 1 ! A - B45 . Diagram Showing How to Add a Stage of Radio Frequency to a Three-Tube ( Regenerative Set. " J By C. J. KELLY In New York Hfirald-Trlbuno. Morn distance, greater selectivity ni an all-around belter set may lie liud by using a stage of tuned radio frequency with three-tube regenerative sols of the type utilizing a variable tickler coll to secure feedback. Although Al-though Intended for tills special type of receiver, the tuned radio-frequency stage may be used to advantage with almost any receiver that Is not neutralized. neu-tralized. Aside from increasing the distance and selectivity of (lie set, the extra stage will permit 'the use of a loop antenna a highly desirable feature these days when stations are only 15 kilocycles apart and selectivity is an Rll-lmportant thing. As the loop has directional properties, interference from man-made static can practically be eliminated by operating the set with tho loop In such a position that it picks up a minimum of interference. Aerial for Best Results. Willi an aerial and ground the set will be found to be superior In some ways to many five-tube radio-frequency sets. The combination of tuned radio frequency and regeneration regenera-tion will make for better distance records. The radio-frequency stage may be built In a small cabinet and placed alongside of the three-tube set. A double-circuit jack has been placed across the secondary tuning condenser to receive the plug to which the two leads from the loop are attached. at-tached. By using this method It only will he necessary to insert the plug to use the loop, the double-circuit jack automatically disconnecting the secondary sec-ondary coll. The loop will be found excellent for use where it Is impossible to erect nn aerial. The set can be installed in nn automobile or motor boat and operated op-erated in a few moments, as It only is necessary to connect the battery leads and insert the plug. The parts for the radio-frequency stage are all standard, and while most fans already have some of tiie parts around their workshop they may be ; I obtained in any well-stocked parts store for very little. List of Parts. The following is a complete list of parts needed to construct the stage: I One radio-frequency coil, one .0005 : variable condenser; one panel, 7 by 10 inches; one baseboard 0 by 6 inches; ; one standard socket ; one rheostat, 30 ohms; live binding posts, brackets and. screws for coil and baseboard. If the coil is to be purchased, any j fixed coupler having enough indue- ; tance in the secondary to permit it to j work over the broadcast wave lengths i (from 200 to GOO meters) when tuned j by a .0005-microfarad condenser can j be used. j To wind the coil at home a com- , position or hard-rubber tube about six j inches long and three and one-half Inches in diameter is used, as it is a ! stock size and will be easy to obtain, j A spool of No. 22 gauge double cotton-covered cotton-covered wire will be ample for wind-Prig wind-Prig the coils and connecting the set. A 10-turn primary and a 50-turn secondary sec-ondary are wound on the same tube, separated by about one-quarter of an inch. He careful to wind both colls in the same direction. After the connections have been checked the rheostats on both the stage and the detector are turned on. Tuning Tun-ing will be the same as with any other oth-er set. The dials will differ slightly (usually a few degrees) because of the circuits not being matched, but both 1 circuits will be in resonance when a ; station's carrier wave is received loudest. - ! Excessive squealing or whistling ' may be caused by reversed primary j leads or too high plate voltage. lie- duce the plate voltage from 45 to 22 volts. If this does not stop the squealing squeal-ing reverse the leads to the primary on the detector coil. j |
