Radio broadcast .. (1922-30)

Various Circuits and What They Mean 313 Check all connections very carefully with the picture wiring diagram given in the second article of this series (RADIO BROADCAST, Jan. 1924). After your own check convinces you that your wiring is correct and absolutely identical with the diagram, it is best to have someone else check it over so that the same mistake will not be repeated. A point of great importance is that the variable condenser of the Neutroformer unit rotary plate terminal be connected directly to the negative terminal of the vacuum-tube socket of the amplifier tubes. It will be noted in the diagram, however, that this wire from the rotary condenser plate terminal of the third from the right hand Neutroformer connects to the+QO-volt terminal of the detector tube. Audio Transformers: Many times, when howling occurs, reversing the connections to the primaries of either one or both of the audiofrequency transformers will remedy the trouble. The drawing Fig. 3 shows the correct arrangement of transformer terminals and also the best plan of connecting the various leads from the transformer windings to the terminals. Fixed Condensers: In special cases, where trouble with balancing out is had, it may be advantageous to cut out entirely the fixed condenser (capacity .006 mfd.) which is connected from the detector tube plate terminal to ground of the negative A and B batteries common lead. Eliminating this condenser and re-balancing carefully will many times secure a very good minimum or inaudible signal balance. Dirty Contacts : Connections which lead from the elements of the vacuum tube to the direct terminals are soldered to the tube contact pins and these soldering connections oxidize and become dirty very quickly. One should see that the bottoms of these tube contact pins are always bright and clean. Neutroformer Mounting: The neutrodyne circuit requires that all electromagnetic coupling as well as electrostatic coupling be balanced or neutralized. Accordingly, the mounting of the Neutroformer is of great importance, and the correct angle that they should be mounted at is 54.7 degrees from the horizontal. A slight variation from this angle will cause trouble in balancing out. If the experimenter drills his own panels, great care should be taken to see that this angle is correct. Be sure that all your connections are OK. Then if your set is built in accordance with the directions given in these articles, the results will repay you many times over for your work. Various Circuits and What They Mean PART III Capacity and Inductance and Their Relation to Tuning in Radio Circuits By ZEH BOUCK In response to our requests to readers for information on just what type of articles they desire, we have received many letters which indicate that the radio public is growing more interested in the theory of their science. It is an obvious fact that greater enjoyment and efficiency can be derived from any type of apparatus when the theory of its action is comprehended. However it is difficult for us to know just how far we may delve into the fundamentals of radio and yet appeal to the layman. Let us know how you like this article, and if you would care for more of a similar nature. — THE EDITOR. THERE are some bits of radio theory which are of great aid to the enthusiast in getting the most from his apparatus. Among these theoretical facts which cannot be scorned with impunity, is what actually occurs during the process of tuning. Just what does happen when one juggles the condenser and inductance dials on the receiving set? Many en thusiasts have wondered, but have been deterred in satisfying their curiosity by the fog of mathematics which more or less covers the theoretical functioning of C (capacity) and L (inductance).* However, the only mathematics of which The reader is advised to read the article on "inductance," appearing in the January RADIO BROADCAST, and which is the second in this series.