Oscar N. Dame
Passengers on the Sound Line Steamers plying between New York City and local ports in conjunction with the N. Y., N. H. & Hartford R. R., have become familiar with a new wireless installation which appeals especially to enthusiasts on the subject because of its apparently practical nature. This system is known as the Massie system, being the invention of Walter W. Massie, of Providence, R. I.
Knowing that Amateurr Work readers are interested in wireless apparatus, a description of these instruments as viewed in operation by the writer is here given.
It would seem that the sending end, that is, the induction coil, is of the same type as those Used in other systems. The secondary discharge is figured as 50,000 volts. This voltage charges a set of glass plate condensers, which may be adjusted to any desired capacity, and with the disruption of the spark gap, a powerful oscillation is set up in the aerial wires, and such transmission is estimated suitable'for'250 miles.
In his coherer, the inventor has certainly accomplished more than his contemporaries, inasmuch as he has developed with simple materials a coherer that responds to feeble waves quickly and positively, and what is more, is subject to immediate decohering without undue tapping. The majority of coherers require blows of considerable force and beside the likelihood of cracking the glass, these violent knocks tend to injure the sensitivity.
This coherer consists of a small glass tube a few inches in length, having a metal cup or plug in the lower end and a brass collar and set screw at the top. A steel spring supported by one end on the baseboard is affixed to the bottom plug. The coherer contains a certain amount of fine silver fillings at the bottom, and on top of this a pinch of soft iron filings. It will be understood that the iron filings are subject to magnetic influence, and the silver ones are not.
Set into an adjustable collar at the top is a fine pointed steel needle, permanently magnetized, the point of which engages a few of the top layers of fillings in such a manner as to crowd them up from the other filings. Thus there is direct connection through the coherer of extremely high resistance. It might be said that the magnetic filings are cohered to the needle at aril times, the direct point of variation being where the two kinds of filings meet. When the oscillating current enters the coherer, the magnetic and non-magnetic filings cohere, greatly lessening the resistance of the circuit and operating a relay as in other systems of wireless receiving.
Decohering is brought about by a tapper which strikes gently against.the free end of the spring supporting the coherer. This style of coherer is adaptable to a signal bell outfit and also to a Morse register.
In regular receiving this system employs a detector of the microphone type, which consists of two knife-edge blocks of carbon on which rests a polished steel needle. The oscillating waves vary the resistance of contact so that dots and dashes sound as buzzes in a telephone receiver connected with battery across from carbon to carbon. This method is not new, but has been improved by the addition of a small steel magnet which rests on the baseboard near the steel needle in a position calculated to exert a certain magnetic force upon the needle and hold it upon the carbon blocks so that it can neither vibrate or roll or otherwise impair the efficiency of the dots and dash readings.
This magnet is very effective and the sensitivity of the instrument may be regulated by drawing the magnet nearer or further away from the needle in order to meet specific conditions of receiving.
It is said that the resistance normally of the oscilli-phone, as the detector is styled, is approximately 40,000 ohms, and after cohesion with the carbon blocks is established by the oscillating current, it dropsto about 700 ohms. It would seem, therefore, that this great variation should prove very effectual in long distance work, and the operator informs the writer that shore stations have found this device accurate for fully 150 miles and that it is in daily use between Block Island and Point Judith, and Nantucket Shoals light ship, and also from the railroad shore station at Wilson Point to the Sound steamers of the company.
It would seem, therefore, that these very workable instruments, all of which are covered by patents, would prove very profitable for wireless enthusiasts to study. A sketch of the oscillator, and also of the coherer, is shown, to more fully explain the text. In the oscillator, the two upright pegs behind the steel needle are placed there to keep the needle from rolling upon the magnet. They are short pieces of smooth rod inserted in the insulated block supporting the two carbons and not electrically connected with anything.