The Birmingham age-herald., 1922-05-28
Making n Bank-wound Coil

Question:. Is 1t desirable to have the aerial lead-in and ground wire equal in wave length to that of the
 sending station, and if so. why? Z.
 What Is the particular formula of an
 aerial? 3. To hear wvP (who is sending 1,45o meters with a regenera- tive receiver) is it necessary to use loading coil in series with the ticker lcoil as well as a loading coil in the primary winding? 4 Can you supply me with information as to making a bank wound tuner up to 2,600 meters? I-T. J. L.
 Answer-1. It is not necessary to have an aerial equal in length to one complete wave length. Such an aerial Is known as the Beverage antenna. and is used for the purpose of elimi- hating static that originates in all directions other than that of the sta tion 1t is desired to listen to. This ! type of aerial is limited in It's appii- cation because of the great length Of ] the wire necessitated. It was de- scribed in these columns solely as matter of interest and as informa- ton to those radio fans who had the space at their disposal to experiment with ?. practical method of deter mining the natural wave length Of the aerial is to measure the complete length of the aerial lead-in and | ground wire in fett multiply 1t by and divide by 3 and the answer will be the approximate wave length of the aerial In meters. For instance. an aerial 100 feet long complete would have a natural wave length of l33 meters B. In order to listen to WvP it will not only be necessary to load the tickler. as well as the primary coil, but. you will also have to place the two loading coils in an inductive relationship to each other. 4. It is very difficult matter to wind bank woup1 coils. For such coil. having /, a wave length range up to 2.6Q0 meters, it will be necessary to take a tube az inches in diameter and 4h inches long and wind it with No. 24 s S. c. wire in three banks You will have to take at least eight taps fl om this coil, It will be necessary to have a special winding device, con
 sisting of two end pieces for your tube. with a shaft and handle. Prac- tice alone, can make perfect this type Of winding, First of all wind three complete turns around the tube, keep ing the wire as tight as possible. At the end of the third turn bring the turns and wind once around, Then wire up between the second and third turns and wind once around. Then another turn betweeen the first and second. At the end of the fifth turn d jump up betweeen the fourth and firth and wind one turn. The result should be pyramid of three turns, then two turns and then one. When the sixth turn has been completed bring the wire down onto the tube
 and put on the seventh turn, the eighth on the seventh, and the ninth on the eighth. Jump to the tube again and repeat the process. To take off taps when the tapping point is reached bend the wire sharply to one side and wind . single turn around the part of the coil already wound. Bring the end of that turn back to where it was started and continue the winding. After the coil has been com Ipleted and varnished cut the tapping turns and take off the taps. This method keeps the winding tight and the taps out of the way. The object oc winding coil in this way Is to eliminate or reduce to a minimum the capacity effect betweeen the wind ings of the coil itself.
 What Distance win Set Recefvef | StlOn--EitdSeT ttli int Aht et PS and probable cost of a radio telephone set that would satisfactorily receive 500 or roo miles, to be installed in the icountry.-A. r.
 Answer-The distance at which you can receive from station depends not upon the receiving apparatus prf- marily, but upon the power of the | transmitting station. Of course. there are receivers that are more sensitive than others, but they. too, depend upon the transmitting station. The ibest tyne of receiving equipment that you can use at the present time is a lregenerative receiver with vacuum I tube detector and two stages of audi freo,,ency application. which will cost you, complete, in the neighbor- hood of $25o. No one, of course. can | guarantee the distance any set Will receive from. 'S
 Interference From A. C. Lines Question--1. have an indoor aerial, consisting of one wire 50
 feet long across the hall, through the | doorway and then across the hall. I hear WIZ we'll but the speeches are not distinctive. Will the addition of
 several 15-foot wires make recep- ton clearer? I cannot use the out door aerial. 2. The aerial I have
 is about 200 feet from the railroad power line carrying a 25-cysle A. c. of 60 amperes at pressures of 1f,o0o
 and 22,00e volta am often bothered
 by loud hum and also a howl dur ing the reception of signals. Do
 you think the railway wires cause 1t. and if not, what would cause this?
 3. see no variable condenser on my I set. Are there any fixed ones used
 on the Aeriola Senior. and, if so,
 where are they placed in the cir yariably caused by too much filameat l current in the tubes. or else too