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Show ELECTRICAL SHOP AND RADIO j ability to cover the entire range of wave length with very small dead-end losses. With the same receiving set the coils used for receiving long wave trans-Atlantic stations can be plugged out, a smaller set of coils plugged In, and amateur stations picked up efficiently. ef-ficiently. This ability tends to make this particular par-ticular type of receiver the closest approach to a universal wave length receiver that can be made, The regenerative circuit arrangements arrange-ments already shown feed back from the plate circuit to the grid circuit In one of two ways : First, conduc-tlvely, conduc-tlvely, as in the circuit called the De-Forest De-Forest Ultra-Audion circuit, and second, sec-ond, by inductive coupling nsjn the circuit which makes use of the tickler coil. There is a third method of coupling electrostatic, by which the circuits between which the energy is to be transferred are connected by condensers. In a circuit in which the energy Is small and the frequency is high, that Is, short wave length, the coupling condenser need be of only a very small capacity. The elements of a vacuum tube have a capacity with respect to each other. Some of the most efficient of the short wave regenerative receivers receiv-ers used today depend on the capacity between the elements of the vacuum tul re to furnish the necessary electrostatic electro-static capacity between the plate and the grid circuits to feed energy from one of these circuits to the other. Figure O shows a simple single tube regedierative receiver for short wave work that depends on the electrostatic electro-static capacity between the elements of the tube for the coupling between the plate and grid circuits. A variometer vario-meter "A" in the antenna circuit is used for tuning. Another variometer "B" in series with the plate is used for tuning the plate circuit to the same natural period as that of the received signal. This circuit Is sometimes culled the tuned plate circuit method of regeneration. There are two tuned oscillating circuits cir-cuits in the receiver. One tuned circuit cir-cuit consists of the variometer "A" with the capacity of the grid to filament fila-ment of the tube across it. The other tuned circuit consists of the variometer vario-meter "1!" with the capacity of the plate to filament across It. These two circuits are in turn electrostatically coupled to each other by the capacity between the grid and the plate. A receiver of the type shown In Figure O Is very efficient, because there are no untuned circuits. In addition ad-dition the energy sent back from the plate .Ircuit to the grid circuit compensates com-pensates for the hisses in the circuits. This results In very high amplifications. amplifica-tions. Though the adjustment of a set of this type Is rather critical, especially tire amount of Induction In the plate circuit, but two knobs are necessary to control the tuning and the amount jf regeneration. With a good antenna Establishment That Does General I Electrical Work Has Big Advantage Advan-tage Over ethers. One of the strongest arguments possessed pos-sessed by the electrical store selling radio supplies is the expert service It can offer, says Burton Millar, hi a comprehensive article in ltadio Merchandising. Mer-chandising. All sorts and descriptions of apparatus and parts can lie put in stuck by any store in any line of business and that Is exactly what U being done in every city in the country, coun-try, but the establishment which makes a specially of doing general electrical work wiring for light, pow- er, etc., and carrying a stock of electrical elec-trical goods of every sort has a distinct dis-tinct advantage over the store which added a radio department to other lines of merchandise entirely different differ-ent In character. It is virtually Important, however, that the availability of this expert service be broadcast to the field it Is desired to reach. Publicity is the only thing that will do It. The public must be told. Not -once, but repeatedly, repeated-ly, and In every possible way. It is not enough to have a card In the display window announcing: "Our electrical experts will be glad to give you uny Information or assistance in 1 installing or operating your radio outfit." out-fit." Or to run an occasional small ad In the local newspapers. Or to have a car card In the local street cars. Or to distribute small folders through the malls to a local list. All of these methods are good If you keep persistently at It! There Is no single quality of advertising so absolutely ab-solutely essential as persistence. If you do not concede this you are simply sim-ply Ignoring the experience of all successful suc-cessful advertisers of all time. If the radio department is to be built up and made a substantial part of your store's business it is essential that the public be told where it can find this superior service, tested apparatus ap-paratus and expert counsel. |