Patent GB-190704713-A (GB)
Title: Improvements in the Transmission of Energy by Electromagnetic Waves.
Inventor: FESSENDEN REGINALD AUBREY
Filed: 1907-02-26
Granted: 1908-05-26
Abstract: 4713. Fessenden, R. A. Feb. 26. Telegraphs. - Relates to the transmission of energy by electro-magnetic waves, and more particularly to means for preventing interference at the receiving-station by atmospheric disturbances or by signals which it is not desired to receive. The oscillations set up in the receiving-antenna pass through the adjustable inductance 2 and divide between the primary coils 7, 8 of two transformers, the path of the oscillations including also the adjustable condensers 11, 12, adjustable inductance 5, and earthed condenser 13. The secondary coils 9, 10 of the transformers are arranged in series with each other and in operative relation to the wave-detector 17. Variable inductances 14, 14<1> and adjustable condensers 15, 16, 18 are arranged as shown. The receiving-instrument 19 is in a local circuit which receives current through the potentiometer 20. Adjustable grounded condensers 21, 22 enable the capacity of the receiving- circuit to be varied. The oscillation circuits through the two primary windings 7, 8 are so adjusted that when waves of the desired periodicity are received there is strong resonance in one of them, and very little in the other, so that the resultant effect on the oppositely wound secondaries 9, 10 is large and the wave-detector 17 is strongly affected. Impulses which have not the desired periodicity divide equally between the two circuits, and these effects neutralize, the wave detector being unaffected. Owing to phase-difference between the currents, complete neutralization may not be obtainable by an adjustment only of the inductance and capacity of the circuits. To meet this difficulty, oscillations may be allowed to pass through a variable resistance 42, a variable inductance 41, and through the winding 39 of an adjustable transformer 40. The phase and strength of these oscillations can be so adjusted that their effect on the circuit which includes the coils 9, 10 neutralizes any unbalanced voltage due to those coils. The phase - compensating device may be inductively associated with the antenna instead of being directly connected, as in Fig. 1, and a variable condenser may be substituted for the inductance 41. Fig. 2 shows a transformer in which the primary winding consists of copper wire wound on a glass jar 24, and the secondary consists of a smaller number of turns wound on a glass jar 25. An electrostatic screen is provided between the primary and secondary windings. This may consist of an earthed copper cylinder 26 slotted vertically ; or the inside of the jar 25 may be coated with gold leaf, or with bronze or gold paint. A large inductance may be placed between the screen and earth. In another form of transformer, each coil is wound in the peripheral groove of a ring of hard rubber. The rings may be coated with gold leaf or metallic paint, or they may be separated by a radially slotted metal disk. Fig. 3 shows in plan view an adjustable condenser comprising a series of semicircular plates 31 carried on a vertical shaft and adapted to be introduced to a greater or smaller extent between the fixed plates 30, which are also semicircular. Fig. 5 shows a tubular adjustable condenser, comprising metal tubes 36, 37 and an insulating-tube 35. Specification No. 17,704, A.D. 1902, is referred to.