Page:United States patent 627650.pdf/2

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To all whom it may concern:

Be it known that I, Guglielmo Marconi, electrician, a subject of the King of Italy, residing at 28 Mark Lane, in the city of London, 5England, have invented certain new and useful Improvements in Apparatus Employed in Wireless Telegraphy, of which the following is a specification.

In the specification of a former patent granted10 to me, No. 586,193, I described a receiver in which the ends of an imperfect contact in a local circuit were connected one to earth and the other to an insulated conductor.

According to this invention the conductor 15is no longer insulated, but is connected to a capacity, which may be the earth, through the primary of an induction-coil, while the ends of the imperfect contact are connected to the ends of the secondary one of the 20connections, being through a condenser.

The induction-coil preferably consists of a few turns of insulated wire. Over or under this first winding, which constitutes the primary, is wound a secondary winding, which 25constitutes the secondary.

In order to obtain the best effects,it is essential that the induction-coil should be of very thin wire. It is desirable that the primary and secondary windings of the coil should be 30close to each other and that the windings of each should be in a single layer. It is desirable that the induction-coil should be in tune or syntony with the electrical oscillation transmitted, the most appropriate number of 35turns and most appropriate thickness of wire varying with the length of wave of the oscillation transmitted.

The capacity of the condenser on the connection between the imperfect contact and 40the secondary of the coil should be varied (in order to obtain best effects) if the length of wave is varied.

It is desirable that the conductor connected should offer a large surface, and therefore 45the use of such materials as broad wire-netting in lieu of wire is desirable. It is also desirable to employ thick conductors or netting or its equivalents at the transmitting end. The introduction of the coil in the conductor not only improves the signals, but also 50prevents to a great extent any interference due to atmospheric influences, as many atmospheric electricity collected by the aerial conductor escapes to earth through the primary of the coil, thus preventing a charge from 55accumulating and discharging itself through the imperfect contact. Any stray interference can be further minimized by substituting a suitable capacity for the earth.

I have used a condenser of about one-fourth60 microfarad capacity for the above purpose.

Figure 1 is a diagram of the arrangement I prefer. Fig. 2 shows a modification. Fig. 3 shows the induction-coil.

In Fig. 1, A is a long conductor suspended65 in the air by insulators, and E is a connection to earth or other suitable capacity. B is a local battery, and R is a relay working a signaling or other instrument. j¹ is the primary of the induction-coil or transformer,70 which is inserted between A and E. k¹ is a condenser placed across the sensitive imperfect contact and the secondary winding of the induction-coil or transformer. c¹ c² are choking coils, their object being to prevent75 the oscillations generated in the winding j² from running into the battery connections at b and d, which would weaken the effect of the oscillations on the sensitive imperfect contact T.80

Fig. 2 shows a somewhat similar arrangement, which, however, does not give such good results as Fig. 1. In this case the condenser k¹ is omitted.

I have obtained good results by employing85 an induction-coil or transformer constructed as follows: The primary j¹ of the said induction-coil or transformer is wound on a glass tube j about .635 centimeter in diameter. The said primary winding consists of two90 parallel windings of two hundred turns each of copper wire .012 centimeter in diameter insulated by a single covering of silk. The resistance of these two winding in parallel is about 3.1 ohms. The secondary winding95 j² of the induction-coil or transformer consists of about eight hundred turns of a similar but thinner wire .005 centimeter in di-