Radio broadcast .. (1922-30)

Record Details:

Something wrong or inaccurate about this page? Let us Know!

Thanks for helping us continually improve the quality of the Lantern search engine for all of our users! We have millions of scanned pages, so user reports are incredibly helpful for us to identify places where we can improve and update the metadata.

Please describe the issue below, and click "Submit" to send your comments to our team! If you'd prefer, you can also send us an email to mhdl@commarts.wisc.edu with your comments.




We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.

Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.

.RADIO BROADCAST. "In these same models, when a pilot lamp becomes loosened or burnt out it is a very hard thing to put your fingers inside the frame of the dial and replace the lamp. After cutting up my fingers it finally dawned upon me to use a rubber tube with an inside diameter equal to the lamp or a little smaller, and about three or four inches long. After the threads are given a start it is then easy to tighten the lamp all the way.) "A good rough indication of the 224 and its respective circuit may be obtained by placing your finger on the cap terminal of the tube. If the music stops it is good. If not, it is most likely to be a low tube and should be replaced as soon as possible as it lowers the efficiency of the other tubes." Servicing Radiolas M. R. BATTERSBY, in charge of the radio repair department of the Manhattan Electrical Supply Company, New York City, sends along the following data on a portable oscillator for servicing superheterodynes: "Some time ago I was called upon to design a really portable 175-180-kc. os- cillator to be used in servicing superhetero- dynes. So with two items in mind, namely portability and minimum cost of construction, 1 built the following oscillator in which a UX-112A tube was used with bat- teries consisting of a 4.5-volt C battery as the A supply (which is good for about 15-20 hours con- tinuous running of the oscillator filament) and B supply consisting of a small 22.5-volt B battery. If greater output is desired two of these B batteries can be used in series, although two are not necessary for satisfactory opera tion. "An aluminum shield can mea- suring 4.5" high by 5" square was cut to measure 2.5" high by 5" square. This was easily accom- plished as the can was of the collapsible type held together by eight screws, allowing the removal of any part. The flat sides and supports were cut with a hack-saw to size and smoothed with a file after which the side supports were drilled and tapped for / 2 screws so that the top could be fastened on again in the original manner. The 5" by 5" top holds all the apparatus indicated in the diagram and the pictures. The well-plannetl service shop of Vaughn's, Inc., Greensboro. N. C., (specialists in Sonora, Majestic, and Crosley receivers. "A feature of the oscillator and one which makes possible its compactness, is the oscillator coil itself which is the secondary coil of an i.f. transformer ay small wire are put on for the pick-up >il. ~ SECONDARY OF R-C-A-N98342 I-F-TRANS 4 MEGOHMS rVWWS 506 WESTON M.A PIN JACKS The complete schematic diagram of a fifteen- dollar home-made portable oscillator. for the Radiola 60 (R.C.A. part No. 8342). The case of the i.f. transformer is taken off, the coil is demounted, and the primary winding is removed. Then four turns of Two views of the portable oscillator described by Mr. Battersby. This in- strument was designed especially for servicing superheterodyne receivers. any coil. The secondary coil is tuned to 180 kc. with the original condenser supplied in the i.f. transformer for that purpose or by means of a balancing condenser (R.C.A. part No. 2239). "For 175 kc. a balancing con- denser (R.C.A. part No. 2239) is paralleled with the 180 kc. con- denser by means of a Yaxley single-pole jack switch. The dia- gram is shown on this page. "After construction, the oscilla- tor is calibrated by means of a Radiola 60 receiver for 180 kc. and a Radiola 66 receiver for 175 kc. The method is as follows: " For 180 kc. the pin jack leads of the 0-5 or 0-10 milliammeter are placed in series with the plate lead of the second detector in the receiver, a Radiola 60. This can be done either by an adapter or by breaking in on the red plate lead at the terminal board. Place all the tubes in the receiver with the exception of the oscillator. Clip a pick-up wire to the middle stator section of the variable condenser bank in the receiver and attach the other end of the wire to the pick-up jack on the oscilla- tor. With the receiver and oscillator both operating adjust the tuning condenser No. 1 across the coil in the oscillator for max- imum reading on the milliammeter which will indicate resonance at 180 kc. If the loud speaker is connected to the output terminals of the receiver the note of the oscillator will be heard with good volume, its pitch depending on the value of grid leak used. "To calibrate the osscillator for 175 kc. throw the jack switch on the oscillator panel to parallel the secondary condenser No. 1 just tuned, with the condenser No. 2, as yet unusued, taking care not to disturb the adjustment of the first condenser. A Radiola 66 receiver is used for this calibra- tion and the procedure is the same as when calibrating with the Radiola 60. The pick- up lead is clipped on the middle stator section of the variable condenser bank in the receiver and condenser No. 2 in the oscillator is adjusted for maximum reading of the milliammeter. After calibrating it is wise to seal the small condensers in the oscillator with a bit of wax to insure the adjustment remaining permanent." [By substituting a coil of about 100 turns, wound on a three-inch form and centertapped, for the R.C.A. No. 8342, this oscillator may be used for service work on the broadcast band.— Editor.] DECEMBER 1929 105