US1720023A - Receiving system for radio telegraphy and telephony - Google Patents

Description

July 9, 1929. F. K. VREELAND RECEIVING SYSTEM FOR RADIO TELEGRAPH! AND TELEPHONY Original Filed Feb. 17, 1917 Patented July 9, 1929.

FREDERICK K. VREELAND, OF MON TCLAI-R, NEW JERSEY.

{RECEIVING-SYSTEM FOR RADIO TELEGRAPHY AND TELEPHONY.

Original applicationfiled February 17, 1917, Serial No. 149,166, now Patent No. 1,407,103, dated February 21, 1922. "Divided and this application filed January 21, 1922.

My invention relates to an improved re ceiving' system for radio telegraphy or telephony whereby the efficiency and clarity of the reception is improved. The invention has for its particular object the elimination of interference by straysor foreign impulses, whether emanating from other radio transmitters or produced by atmospheric or static disturbances. \Vhile the invention is highly effective in excluding artificial radio oscillations of foreign frequencies, it is particularly adapted to the much more difficult function of preventing objectionable interference with the received signals by atmosphericor static strays. The difficulty of successfully overcoming or preventing the disturbances due to atmospheric .or static strays arises not only'from the great intensity of such disturbances, but particularly from the fact that they are not simple harmonic oscillations, but are usually. strongly damped or aperiodic. Such damped impulses are capable of exciting oscillations in a tuned resonant circuit, irrespective of .its frequency, and therefore .they cannot beeliminated'by ordinary methods of tunin In my said Patent No. 1,407,103, of which the present application is a division, I have described a receiving system including a baffle circuit .or circuits in combination with intensity selectors which is highly effective in eliminating the effects .of stray impulses on the receiving system. In that patent I described, but did not specifically claim, means for preventing the setting up and transmission of detrimental shock oscillations in the receiving system. The invention claimed herein has for its particular .object the prevention of such shock oscillations and their detrimental effect on thereceiver.

In order that .the invention may be better understood, attention is directed to'the ac companying drawing forming apart of .this specification.

Figure 1 shows an arrangement including a symmetrical baffle circuit and Figure 2 shows a similar arrangement including an asymmetrical 'bafile circuit.

As I have explained in the above mentioned patent, the difficulty in eliminating the effects of atmospheric strays on the recei ver is due largely to the fact that they are usually strongly damped or aperiodic impulses. When such an impulse is im- Serial No. 530,816.

pressed on a tuned circuit it tends to excite oscillations in this circuit, irrespective of the frequency to which it is tuned, and such shock oscillations produce a disturbing effect on the receiver. The purpose of the present invention is to prevent the production of such shock oscillations and the transmission of disturbing impulses to the receiving system. This is preferably accomplished by making at least a part xof the receiving s stem with sufficient damping .to prevent t e setting up of free oscillations (therein, and, it may be, also by coupling such part of the receiving system to the remainder of the system by a coupling sufficiently loose to prevent the .transmission of such strongly damped currents asmaybe excited'bypowerful aperiodic or strongly damped strays.

In Figure 1 of the drawing, which shows a simple embodiment of the invention, A is a. collecting element which is here shown as an ordinary .antenna, B isa loading-or tuning coil, and E is a receiver circuit inductively connected to thecollecting circuit by a transformer p The receiver circuit E includes a detector D, which is shown as an electrostatic telephone serving also in :a tuning capacity. The electrostaticdetector D is excited .by a sustained oscillation, of slightly different frequency from the sustained signal oscillation, produced by a local oscillator or generator G coupled to the receiver circuit by a transformer p The connection between. the receiver circuit E and the antenna A includes baflie elements T, T T T T T, ,'T, T each comprising an inductance .L and capacity C, and each tuned to the signal frequency, A plurality of electrolytic cells or other intensity selective devices 8,, S and S, are shunted across the baffle element-sat a, 6,, a, b, and a, 7J3, thesepoints being points of small potential difference for the signal impu'lsesbut relatively large potential difference for strays or foreign impulses. An oscillation transformer p 8 couples the baffle circuit to the receiver circuit E. Each cell 8,, etc., is so designed and constructed as to offer free passage to impulses beyond a given intensity applied .to its terminals, while excluding weaker impulses. Powerful strays picked up by the antenna are thus shunted through the cell S to the ground, and the residue shunted by the other selectors S and S While the weaker signal impulses are excluded from the by-pass and find free passage through the baffle elements T T,, etc, to the receiver circuit E, where they are superimposed on the local oscillations of slightly difierent frequency produced by the generator G, thus producing beats which are detected by the amplifying detector D.

The baffle elements T, T,, etc, greatly increase the effectiveness of the intensity selective devices S,, etc., because of their frequency selective property. Being tuned to the signal frequency their reactance to the signal impulses is zero, but their reactance to any other frequency is high. The points a, 1),, etc., therefore will be points of small potential difference at the signal frequency, but of relatively large potential difference for any other frequency, or for aperiodic impulses, which thus tend more strongly to escape through the by-pass. By this combination of an intensity selective device S,, etc, with a frequency selective device T, T,, etc, the effectiveness of the intensity selective device is greatly increased. It thus acts preferentially to divert from the receiver circuit not only strays that are stronger than the signal impulses but may even divert strays that are much weaker than the signal impulses since such strays are impressed upon it with proportionately greater intensity than the signal impulses.

The electrolytic cells or other intensity selectors S,, S S, are made progressively sensitive. The first selector S, is made rugged so that it will not be injured by the most powerful atmosphere disturbances. This will divert in large measure the most powerful strays. The residue which is not diverted but succeeds in passing the baffle elements T, T, then encounters the baflie elements T T, and is diverted by the more sensitive selector 5,, and this process may be repeated until the strays are practically eliminated.

While the use of the baffle circuit or frequency selective device is thus highly de sirable in connection with the intensity selective device, it is not essential and the apparatus will be effective even though the cell shunts strong signal impulses to the same extent that it shunts strays. In such case weaker'signal impulses, or the remnant of strong signal impulses which is not diverted, will be amplified by the receiver so that they will produce a stronger signal than such remnant of the strays as may escape the bypass and enter the receiving system. The baflie element is desirable, however, not only to increase the effectiveness of the intensity selector, but also for an additional reason which I will explain.

When the local exciting current of a beats system is large with respect to the signal current, oscillations of considerable intensity may escape through the transformer 79, 5. These oscillations, if applied to the cells S,, S etc, in full force, might be so powerful as to impair their effectiveness in diverting strays. By the use of the baifie elements T, T,', etc., their effect on the intensity selectors may be reduced to any desired value, since the points a, 6,, etc, will then be points of small potential difference to the local oscillations as well as to the signal impulses, the difference of frequency being small.

Preferably I employ the intensity selective device in connection with a receiving system having a baffie circuit offering but little impedance to the signal impulses but great impedance to the strays, as I described in Letters Patent No. 1,315,584, dated September 9, 1919. It is also desirable, though not of coursenecessary, to utilize with the system a receiver operating on the beats principle owing to its inherent stray-reducing power.

The invention is not limited to use with an amplifying detector, nor with the beats system of receiving, but it is also applicable to other receiving systems, including receivers of damped oscillations from an ordinary spark oscillator. lVith such a sysstem it is usually desirable to employ a plurality of intensity selectors, together with a plurality of baffle elements. Two examples of this type are shown in Figures 1 and 2. In the former I have illustrated a beats receiver; in the latter an ordinary receiver of damped oscillations, though either type of receiver might be used in either arrangement.

Inasmuch as a powerful aperiodic or strongly damped stray may excite oscillations in a resonant circuit, irrespective of its frequency, at least a part of the receiving system should be made with sufiicient damping to prevent the setting up of free oscillations therein. Preferably the first baffle unit, which, in the arrangement shown, is the one directly associated with the collector, should be so strongly damped as to be aperiodic and incapable of sustaining and transmitting free oscillations to the receiver circuit. Thus in Figure 1 that portion of the baffle system which comprises the baffle elements T, and T, is so constructed that it cannot sustain prolonged free oscillations and it is coupled to the remainder of the system by a transformer 10, 8, whose coupling is sufiiciently loose to prevent the transmission of such strongly damped currents as may escape the intensity selector S,. r The requisite damping may be introduced by suitably proportioning the resistance and other energy consuming elements of the circuit with respect to the reactive elements, or by other equivalent damping means. The damping of the circuit T, T, and the loose coupling of the transformer 10, 8, should not however be sufficient to obstruct the passage of the relatively small self-induction and large c2 pacity. The succeeding battle elements T T etc., should be more heavily loaded in progressive sequence. An adjustable resist-- ance R,-or its equivalent, may be included in the baflie circuit T T, if desired to control its damping.

While I prefer to arrange the baflie elements symmetrically on opposite sides of the receiving circuit, this is not necessary. The lower series of bafiie elements may be omitted and each by-pass directly ground as indicated in Figure 2. Preferably, however, at least one bafiie element T,, Figure 2, is retained between the receiver circuit and ground, to eliminate any disturbances that might result if the ground connection had a. considerable impedance. The receiver circuit shown in this figure comprises a detector D and the usual tuning elements C, s.

The invention is not limited to the use of any particular form of intensity selective device, nor to the particular arrangement of apparatus shown, but is applicable to a great variety of systems including equivalent means for preventing the production and transmission to the receiver of shock oscillations by the action of strays. The particular arrangement shown in the drawing is the same as that shown and fully described in my said Patent No. 1,407,103 and its specific features, not forming an essential part of the invention sought to be covered in the present application, need not be described in detail.

Having now described my invention and what I claim is new therein, what I desire to secure by Letters Patent is as follows:

1. In a receiving system for radiant energy, the combination with an antenna or collecting element, of a receiving apparatus and a tuned damping circuit, transmitting signal impulses freely to the receiving apparatus and including damping means for preventing excitation and transmission of free oscillations excited by strays, and an intensity selective device associated with the tuned damping circuit, substantially as set forth.

2. In a receiving system for radiant energy, the combination of a collecting element, a receiving apparatus associated therewith, means for preventing the excitation of shock oscillations in the collecting element, a bafile element affording free pas sage to the signal impulses but obstructing the flow of foreign impulses and strays, means acting preferentially to divert the energy of shock impulses from the baflle element, and means for transmitting signal oscillations from the collecting element'to the receiving apparatus, substantially as set forth.

3. In a. receiving system for radiant en ergy, the combination of a collecting ele ment, a receiving apparatus associated therewith, means for preventing theexcitation of shock oscillations in the collecting element, frequency selective means for. transmitting signal oscillations from the collecting element to the receiving apparatus, and intensity selective means cooperating with the frequency selective means to divert preferen tially the energy of shock impulses, substantially as set forth.

4. In a receiving system for radiant energy, the combination of a collectin ele ment, a receiving apparatus, a baffle element tuned to signal frequency associated with the collecting element and the receiving apparatus, means for preventing the excitation of shock oscillations in the collecting element, means associated with the baflie element at points of small potential differences at signal frequency for diverting the energy of shock impulses, and means for transmitting signal oscillations from the collecting element to the receiving apparatus, sub stantially as set forth.

5. In a receiving system for radiant energy, the combination of an aperiodic circuit with associated collecting means, a baflle ele. ment tuned to signal frequency transmitting signal energy therefrom, means cooperating with the battle element to preferentially divert and dissipate the energy of shock impulses, and means for receiving the energy of signal frequency.

6. In a receiving system for radiant energy, the combination of an aperiodic circuit with associated collecting means, a baflie element tuned to signal frequency transmitting signal energy therefrom, intensity selective means cooperating with the baffle element to preferentially divert and dissipate the energy of shock impulses, and means for re ceiving the energy of signal frequency.

7 In a receiving system for radiant energy, a collecting system incapable of sustaining and transmitting free shock oscillations, a baffle element, including balanced reactances, receiving signal energy therefrom, a by-pass shunting said bafiie element containing means for dissipating stray energy, and means for receiving signal energy from the collecting system.

8. In a receiving system for radiant energy, a collecting system incapable of shock oscillations of signal frequency, an aperiodic bafiie element, including balanced reactances and damping means, receiving signal energy therefrom, a by-pass shunting said bafiie element containing means for dissipating stray energy, and means for receiving signal energy from the collecting system.

9. In a receiving system for radiant energy, a collector, a baflle element, including balanced reactances and damping means for preventing the excitation of shock oscillations therein, transmitting signal energy from the collector, energy dissipating means by-passing the bafile element, and means for receiving signal energy transmitted by the baflle element.

10. In a receiving system for radiant en ergy, a collector, a branched circuit receiving energy therefrom, one branch, comprising balanced reactances and damping means,

transmitting signal energy, the other branch comprising means for dissipating stray energy, and signal receiving apparatus operated by signal energy transmitted by the balanced reactances. I

11. In a receiving system for radiant energy, an aperiodic collector, a branched circuit receiving energy therefrom, one branch, comprising balanced reactances and damping means, transmittingvsignal energy, the other branch comprising means cooperating with the balanced reactances to operate preferentially'on abrupt non-signal impulses, and signal receiving apparatus operated by signal energy transmitted by the balanced reactances. a a a This specification signed this 19th day of January, A. D. 1922.

FREDERICK K. VREELAND.

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