Radio Digest (Apr 1925-Jan 1926)

«**89>"<*i*v"*'£*^* 22 RADIO DIGES T— Illustrated August 8, 1925 Questions and Answers Selectivity vs. Range (14102) DEI, Big Horn, Mont. Q. — I have a five tube Radio set. I do not have very good luck in being able to separate one station from another in a range of 5 degrees. Stations KGO, WCBD, WLS, and WDAF are all strong stations and when they are all on the air about the same time, unless the air is very clear, will give me quite a good deal of trouble to separate. I use an antenna of 7-strand plain No. 22 gauge phosphor bronze wire 100 feet long, stretched taut at a height of 28 to 32 feet high and a lead-in wire of 36 feet, insulated. I have it stretched in a northeast direction from the set. Does it make any difference as to the direction the antenna is stretched from the receiving set? "Would I have better receiving if I used another kind of antenna? I do not have any of the described .city noises to trouble me as I live 10 miles from the nearest electrical appliance. How can you tell whether the ground wire is well grounded or not with this set? If you haven't a battery voltmeter to test B batteries how can I tell when they are almost run down? Is there any disadvantages in using four 22%-volt B batteries rather than two 45-volt B batteries? Are any of the static eliminators advertised in the Radio Digest of big enough success to pay me to add one to my set? If so, which one would you recommend me buying or can you give me some arrangement I may add to my set to help eliminate some of this summer static. As the Radio Digest does not receive compensation for answering questions, will make up for it by trying to get circulation enlarged among my neighbors this coming fall and winter. A. — Relative to your difficulty with selectivity, or the lack of it, we wish to advise that on this receiver, or any other of similar type, you cannot have a coast to coast range or a Chicago to San Francisco range in summer and still have selectivity. Part of the tremendous range which you have is the result of your use of a 100-ft. antenna wire and in the writer's opinion it will be impossible to have good selectivity with such a comparatively long aerial. If you will cut down the length of the straightaway wire to about 60 feet, which will give you an over all length of 96 feet, including lead-in, the selectivity should be considerably helped. There is no way of testing for a good ground other than putting in the very best that you can with well soldered connections or putting in three or four to different points such as the cold water system, the radiator and anything else you can think of, and use them all at once. There is no way of testing B batteries without the use of a meter. There is no difference in efficiency between the use of four 22%-volt B batteries as against two 45-volt B batteries. Although the static eliminators advertised in Radio Digest will work in some locations and eliminate about 25 to 40 percent of the static, none of them will work in all locations nor will they eliminate more than about 40 per cent of the static without a noticeable decrease in volume. The writer neglected to mention above that shortening the aerial from 100 to 60 feet will slightly decrease the volume and may make reception of a few very distant stations impossible in sum ATTENTION please. Is it worth 25c and an hour's work to you to improve your tuning? If so 25c will bring you complete data of a device that you should not be without. St. Paul Radio Improvement CO. P. O. Box :nri3-H, St. Paul, Minn. mer time but the selectivity on those that Vou can still hear with loud speaker volume will be much improved and next fall and winter you will again be able to have a coast to coast range. Ground and Aerial with. Super-het (14114) CN, Evansville, Ind. In your May 3, 10, 17 and 24, 1924 issues of the Radio Digest you described an eight tube super-heterodyne receiver made to work on a loop and I want to know how I can adapt this receiver to work on a regular outside aerial and ground. Also in your June 27, 1925 issue you described an eight tube super-heterodyne receiver made to work on a loop and I want to know how I can adapt this receiver to work on a regular outside aerial and ground. A. — We wish to advise that any superheterodyne designed to work on a loop aerial can be used with an outside antenna by connecting the two terminals intended for the loop leads to the secondary terminals of an antenna coupler. Such a coupler should have about 42 turns on a 3-inch tube or 56 turns on a 2%-inch tube as a secondary while the primary should have from 6 to 15 turns. The coupling between primary and secondary should preferably be very loose and the primary should be on a rotor. In case the super-heterodyne is designed for a center tap loop, the center point of the secondary coil should be determined and the three terminals from the receiver connected to the two ends and the center point exactly as though it were a loop aerial. For diagrams and some definite information we refer you to our issue of March 7 in which we started a. series on the Four Filter Super-heterodyne and the first article showed the connections whereby the super may be connected to a loop by plugging in two jacks or connected to an antenna coupler automatically by withdrawing the loop jacks. To Catch Lower Waves (14004) FB, Scales Mound, 111. I have a homemade neutrodyne which works fairly good except that I cannot get stations much below 275 meters. KYW comes in at about 64 on my dials. I am using Cardwell 17-plate condensers and homemade neutroformers having 6 turns of primary wound on 2% -inch tube (outside measure) and spaced about -feinch apart, 60 turns of secondary with a tap at the fifteenth turn and wound on 3-inch tubing (outside measure). I used 24-gauge silk covered wire. I would like to know what changes should be made in the neutroformers so that I could get down to about 200 meters. A. — First of all tune in KYW, which you say comes in at about 64. Then disconnect the secondary of your second neutroformer from the grid of the second tube and take off about five turns. Do not touch the settings of the variable condensers while doing this. Then con Learn the Code Alphabet a new way in few minutes. Chart with full instructions 50c. No stamps. Triumph Sales, Box 402, Fort Wayne, Ind. Radio Tubes Exchanged Send us your old tube — any make — any condition— and we will send you our Brand New Guaranteed Tube, of whatever type you ronuire (except WD-11), for grt — mm $1.75. All shipments by In » T /O sured Parcel Post C. O. D. JL r n D Bend no money — order today... i»u.i/. DAVENPORT RADIO CO. 327 S. LaSalle St. Chicago, III. WD-11 diotron Buy Tubes ' by Name WD-11 Radiotron nect the secondary to the grid and turn the second dial until KYW is again heard. Continue this process, leaving the first and third dials at their settings until KYW comes in at about 92 on your center dial. Do the same with the other two neutroformers and you will find that with KYW at 92 you can go much farther down on the wave length range and probably can hear stations at 220 meters. The set will have to be reneutralized, however, to allow for these changes. Using' Wrong Tubes? (14105) PCH, Erie, Pa. I have a Branston Super-het, all the parts, and it is a nice looking outfit in the wiring and assembling. I have built it as specified in booklet that I got with the parts. The set has short radio frequency, three stages of intermediate radio frequency and two stages of audio frequency. The whistles and noises in the set caused by oscillation are something awful. It is the same with the loop on or off. In order to bring in a station I must turn the rheostats on full and the whistles and noises ruin all reception. I have been using condensers in all places in the set but the whistles and howls are the same. For grid voltage I have been using 3 to 9 volts; for plate voltage, 90 to 135 volts, and for detector voltage, 45 volts. Grid leaks have been tried in all capacities. It is a Branston reflexed super-het using 7, 201A tubes, Kit No. R-199, cabinet size 7x21x9% inches. A. — We wish to advise that the probable cause of your trouble is that you are using the Branston Kit designed for 199 tubes with tubes of the 201A class. The reflexed super-heterodynes will all work well with 199 tubes but they do not work well with the 201A tubes. You might write to the manufacturers of this kit and see what they can suggest. Underground Aerial Cnts Static (14058) LFW, Conway Springs, Kan. Which gives more volume, TJV-199 tubes or TJV-201? Has there been any kind of instrument devised which will reduce static a little at least? A. — We wish to advise first of all that the 201A tube will give more volume than the UAr-199. The energy that will be delivered by a tube may be measured by the amount of filament energy consumed and this may be figured by multiplying the volts times the amperes. Since 5 times .25 is greater than 3 times .06, the 201A gives the greater volume. There has been no device or instrument developed that will reduce static dependably and under all conditions. An underground antenna, such as was recently described by Mr. E. T. Jones in Radio Digest, will work in the majority of cases and will reduce about 90 per cent of the static. INDUCTIVE TROUBLES (Continued from page 20) wire wound on a 3% -inch tube. The grid coil is composed of 40 turns of number 26 dec. wire wound on a 3-inch tube. Tuning condenser is of .0005 mfd. maximum capacity and variable. For the tubes used, the rheostat has a resistance of 10 ohms, and the ammeter a range of 0 to .5 ampere. Grid condenser is fixed with a capacity of .00015 mfd. while the grid leak has a resistance of 2 megohms. It will be noted that jack number 1 is not wired in the usual way to permit of reception on the detector alone but is connected in such a manner as to provide audio amplification when it is desired to use auxiliary apparatus in connection with current variations audio frequency only. 4$0* MoV*"^ 10 Volumes 8, 9, 1 0, 1 1 and 1 2 Full of valuable information for every set owner. Antennas of various types have been described, the care of batteries is gone into thoroughly, there are pages and pages of tuning hints. Hookups that give the experimenter many hours of pleasure and experience, complete how-to-make articles on various types of sets. A score of illustrated articles on the country's most popular stations and the artists they secure. A year's subscription to Radio Digest at $5.00 brings you 52 issues with all the live news of Radio — broadcasting, invention, construction, programs, illustrations. 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