The Birmingham age-herald., 1922-07-09

r reached, which results in a terrific owl that can be heard all over the room. This Is regeneration, and in d wireless circuit the ticker coll | does just exactly the same thing. 3. A vario- coupler and variometer look something alike, but their fune- tions are entirely different. Both consist of a primary winding of wire that Is placed on a rotating tube or ball inside of the primary winding. ! In the vario coupler the primary winding is tapped off so that you can bring any number of turns or ! wire into the Electrical circuit. The secondary winding is independent Of the primary so far as direct electri- cal contact is concerned, but 1t Is msgnetically coupled to the primary. The amount of current that will be induced in the secondary when the current passes through the primary depends upon the exact position or the secondary coil. so that you will see that 1t is possible to vary this amount of current in the secondary. The vario-coupler is, in reality, an electrical transformer for high fre- quency currents which are received by your aerial wires. The var1o- meter is a tuning instrument, which consists of a primary and secondary in one continuous winding. In other words, the secondary of this fnstru- ment is connected electrically to the primary and It's operation depends upon whether the secondary is in ductiveIy coupled to the primary or whether 1t Is magneticaliy opposed. By turning the secondary completely around 1t can be put in opposition to the primary and a minimum amount of current will flow through the instrument. 4. "VT," in this case means vacuum tube detector" A UV 200 will do for this purpose and the Uv POI will act as an amplifier. In order to put the matter more simply before you, the best circuit that can be employed for reception of broad cast entertainment Is the vario- coupler two-variometer type, and with this you will need yario- coup Ter and then a variometer In the grid circuit of your detector tube and A variometer in the plate cir cult of the detector tube. in addition to the usual standard parts of vac uum tube set.
 Regeneration With Crystal
 o. Could I makf a regenratiyN receiver, using a crystal detector' and how would connect 1t upi H. W. K. =
 A. Regenerative cannot be ob- tained with a crystal detector. The crystal will only act as rectitiei of high frequency currents such as are received in wireless. In other words, it's function is to chop the current in two and permit only one half of the alternations to pass through to the telephone receivers. In this respect, it iacts in just the same manner as the valve In a water pipe.
 Using Light Circuit for V. T,s o. Can I use 110-volt D. c. cut down by means of lamps connected in series to light the filament of a vacuum tube and supply the plate current? E. A. H.
 A. This, of course, can be done. but from a practical point of view 1t is absolutely unsatisfactory. due to the fact that the commutator ripple of the direct generator will be reproduced and multiplied by the vacuum tubes in your telephone cir cut. This disagreeable rattel. which spells the music and speech, cannot be entirely eliminated, although it can be considerably reduced by means of appropriate filter circuits. AS this entails an awful lot of extra apparatus and careful adjustment, it is not worth the trouble, when you can get such good results from the ordinary six-volt storage battery and high voltage "B" batteries.
 Why the Set Howls
 Q. Why does my set howl when tlckler cell Is close to the secondary coil? c. J.
 A The reason that your set howls when the ticker is close to the sec ondary coil is because you are get ting too much regeneration and the tube begins to oscillate. You should place the tickler as close to the sec- at just that point where the SC, starts to howl.
 Using Radio Republication
 v. Could two stages of radio Frequency be added to my R. c. set. which l now have? Should like to know whether there are any firms now making this form already built. so that l could add to the set that now have; also, what transform CTS you would use if building the set and where to get diagrams?
 A. There Is not, to the best of my knowledge, any complete set us- ing radio-frequency amplification. The Radio Corporation of America claim that they have evolved a sys- tenn whereby radio frequency can be added to the regulation regenerative set Personally, I am of the opinion that radio frequency amplification is still in an experimental stage, ard should not like to give any advice of positive character concerning 1t. Under the circumstances, there Tore, l would suggest that you get in touch With the Radio Corporation l of America for complete information concerning this form of amplffica tion. It is possible, however, to add two stages of radio-frequency ampli- fieation, according to their claim. The additional apparatus required is an aerial truning coil. one radio ire | quency transformer, two battery | potentiometers and two amplifyine tubes with socket and rheostats. What the Potentiometer Does c. Please explain the function of the potentiometer that is placed across the "At battery in the vacuum tube sets Some wiring schemes show it, and soine do not. I have not been able to learn the reason.-D. c. l A. The potentiometer is placed across the "A" battery in order to give better control of the entire sys- tenn of circuits. It aids in eliminat- I ing some of the local noises caused | by the batteries themselves, Where ever the potentiometer is used the negative lead from the "B" battery Is connected to the sliding contact or variable portion of the potentio- meter. The potentiometer is then varied until the best point for the movable contact is obtained. This instrument gives much steadier re- suits from the vacuum tube circuit than is obtained in the circuit that does not use it.
 Using Variable II Batteries l O. Does 1t make any difference if