US1869894A - Radio beceiving system - Google Patents

Description

Aug.2, 1932. A. HAZELTINE RADIO RECEIVING SYSTEM Original Filed Feb. 27, 1925 INVENTOR ATTORNEYS Patented Aug, 2, 1932 UNITED STATES PATENT OFFICE LOUIS A. HAZELTINE, OF KOBOKEN, NEW JERSEY, ASSIGNOB 1'0 HAZELTINE CORPORATION, .A CORPORATION OF DELAWARE RADIO RECEIVING SYSTEM Original application filed February 27, 1926, Serial No. 12,000, new Patent No. 1,648,808, dated November 8, 1927. Divided and this application filed October 24, 1925. Serial No. 84,538.

This invention relates to wave signaling systems, particularly to regenerative or heterodyne radio receiving systems, and has for its object the prevention of radiation of lo- (,1 cally generated oscillations especially from the antenna of such receiving systems.

Oscillating or regenerative receiving systems, with consequent radiation therefrom, have been the cause of serious interference with satisfactory reception by other receivers in the neighborhood. This type of interference has become so acute in certain densely populated portions of the United States as to render satisfactory broadcast reception impossible.

The invention described in the present application, which is a division of my copen ing application Serial No. 12,000, filed February 27, 1925, issued November 8, 1927, as Patent No. 1,648,808, provides extremely simple but adequate means for preventing undesirable radiation of locally produced oscillations, and at the same time provides a radiofrequency amplifier which increases the sensitivity and selectivity of the receiving system in which it is incorporated.

These results are accomplished by interposition between the antenna system and the local radio-frequency oscillatory source, of a tuned radio-frequency vacuum tube amplifier, in one or more stages, with complete elimination of coupling between anode and control grid circuits of the tubes, except through the mutual conductance thereof on which the amplifier action depends.

The effective elimination of coupling between the anode circuits and the grid circuits is accomplished by the cooperation of three steps: First, the arrangement of the amplifier transformers so that there is no magnetic coupling between any two of them; second, the avoidance in the wiring of any substantial impedance common to two or more tuned circuits; and third, the neutralization of the natural capacity coupling inherent between the tuned circuits, including particularly that due to the capacity between the grid and the anode of the vacuum tube.

The elimination of undesirable coupling between anode and grid circuits of the vacuum tube, results in prevention of retroaction or regenerative feedback within the amplifier, and also serves effectively to localize oscillations of the source in the output portion of the amplifier, and to prevent their being communicated to the antenna system to be radiated therefrom.

The single figure of the drawing illustrates diagrammatically an extremely simple embodiment of the present invention as applied to radio receiving systems.

The receiver shown comprises two vacuum tubes, A and D, the first of which functions in a neutralized tuned radio-frequency amplifying stage, and the second comprises the customary detector or rectifying tube, which is here made regenerative or continuously oscillating by tuning the anode circuit with a variable inductance L. Such an arrangement is particularly suitable for radio reception of unmodulated continuous-wave signals by the heterodyne method, and, as outlined above, has the advantage over the usual regenerative receiver that the oscillations pro duced by the detector tube are not communicated to the antenna, Where they would cause objectionable radiation. Another useful application of this device is in the reception of damped or modulated waves, wherein, by causing the detector to oscillate, the carrier waves of an unknown station ma be picked up by the well-known beat met od.

Referring to the drawing, the radio-frequency signaling system comprises a current collecting device or antenna A and ground G tapped to a coil Ta having in shunt thereto a variable condenser Ca for adjusting the system selectively to receive signals throughout a range in frequency. Vacuum tube A operating as an amplifier, is arranged with control grid Gr and filament or cathode K connected to the tuned input portion Ta-Ca for transferring signals therefrom through the cathode K and an anode or output electrode 0 of tube A, to the succeeding or output system.

The output system includes av transformer T tunable as a unit to the selected frequency by variable condenser C in shunt to the secondary winding L of the transformer. In

this manner the signals are impressed between cathode K, and control grid G, of tube D which functions as a detector due to the interposition of a grid-condenser and leak-resistance M in series with the control Additionally tube D becomes a radio-frequency oscillatory source! providing optionally regenerative or heterodyne detection by virtue of the cooperant action of variable inductance L, included in circuit between cathode K and anode of the tube, and the inherent capacity C, existin between anode 0' and control grid G whic cause the output portion of the tube to react in aiding phase upon its input portion thereby producin or tending to produce oscillation.

he received signals are rendered audible by headphones H so arranged in the output portion of tube D as to be traversed by the rectified signals, the hi h-frequency components being by-passed y condenser C The usual potential supply sources B and B; are connected to energize the cathode and anode circuits of the tubes A and D in common. The cathode or filament current is controlled by interposed rheostat R. With the single stage of radio-frequency amplification shown, sufiicient negative bias for the control grid G of the amplifier tube A is obtained by merely connecting it to the negative side of the cathode as shown in the amplifier tubes as disclosed more particularly in my mentioned patent, especially in Figs.

gin and 6 thereof and accompanying descrip- The localization of the oscillations in the detector tube is accomplished by elimination of undesirable couplings between the grid and plate circuits of vacuum tube A largel(y through the use of neutralizing condenser in combination with a portion L of secondary coil L closely coupled to the rimary winding L of transformer T oupling between the anode and grid circuits of tube A, due to the natural capacity C between the anode and grid electrodes, together with apparatus associated therewith, is neutralized by the neutralizing ca acity (3,, connected between the control grid and the portion L of the secondary winding L of transformer T This auxiliary coil L or neutralizing winding, is, in this example, that ortion of the secondary winding of transormer T which is included between the tap 1 and the low-potential end 2 of the secondary winding.

As explained in my U. S. Letters Patent Nos. 1,489,228 and 1,533,858, neutralization of the undesirable capacity coupling will be effected when the primary winding L of transformer T and the neutralizing winding L, thereof, are closely coupled electromagnetically, and so arranged with relation to each other that the corresponding terminals (as 1 and 1', or 2 and 2') of the respective windings are of opposite clarity, the ratio of the number of turns of t e neutralizing winding L to the number of turns of the primary windin L, being equal to the ratio of the value of t e undeslrable coupling capacify C to that of the neutralizing capacity With the capacitive coupling between control grid and anode thus neutralized, any residual couplings occurring between input and output portions of the amplifier ma be eliminated to any required degree of refinement by employment of one or more of the various expedients disclosed in my parent application, now Patent N 0. 1,648,808. For example, magnetic couplin between any two transformers such as T an T may be eliminated by mounting them with their axes parallel and at an angle of substantially degrees with the line of centers, as more fully described in my Patent No. 1,577,421 issued March 16, 1926. Residual capacitive as well as magnetic couplings may be eliminated by use of suitable shielding. By-pass condensers may be utilized to provide lowimpedance return paths for the radio-freuency grid and anodewcircuits directly to t eir respective cathodes, thus eliminating couplings due to the use of common potential-supply sources and the like. As stated in my mentioned Patent No. 1,648,808, the requisite refinements in elimination of couplings increase with the number of amplifier stages employed.

In order to simplify the disclosure, the embodiment of the present invention as described is shown as including but one neutralized tuned radio-frequency amplification stage. It is obvious, however, that the fundamental arrangement illustrated herein may with great success be enlarged to include two or more stages of tuned radio-frequency amplification, the vacuum-tube coupling capacity in eachstage being neutralized according to the method herein described. Again, any of the vacuum tubes utilized for radiofrequency amplification, except the tube coupled directly to the antenna, may be arranged to be regenerative, instead of, or in addition to, the detector tube.

A articularly effective radio receiver for broa cast reception may include two stages of neutralized tuned radio-frequency amplification, a regenerative detector, and two stages of audio-frequency amplification. If the tuned radio-frequency amplifier be designed for maximum radio-frequency amplification, no great increase in amplification or selectivity will be noted through the employment of regenerative action in the detector. However, it is at times convenient to use a regenerative detector so that unknown transmitting stations may be tuned in by means of the well-known heterodyne or beat reception method. The radio receiver herein provided may thus include a regenerative detector, or other source of oscillation, and at the same time be incapable of radiating energy which is likely to interfere with other radio reception in the vicinity.

It is to be noted that, while the means illustrated for causing the detector to become regenerative, or oscillating, comprises a variable tuning inductance L inserted in the plate or anode circuit of vacuum tube D, whereby energy in the anode circuit will be fed back into the grid circuit through the inherent grid-anode electrostatic capacity of the tube, other well-known methods for facilitating and controlling the transfer of energy from the output circuit to the input circuit of a vacuum tube may likewise be employed. For example, the inductance L could be electromagnetically coupled to the secondar winding of transformer T and thereby unction as an electromagnetic feed-back or tickler coil. Other known methods which may likewise be used to obtain regenerative reactions may comprise coupling the output circuit to the input circuit of the vacuum tube by means of added capacity, self-inductance, or resistance, common to those circuits.

It will be obvious that the present invention may be applied with merit to any receiving system wherein it is desired to prevent oscillations from being radiated from the antenna, regardless of whether such oscillations are continuously generated, as in the super-heterodyne receiving system, or whether they be only occasionally produced, as in the usual regenerative detector.

I claim:

1. In a radio receiver adapted to be connected to an antenna system, a radio-frequency amplifier including at least one vacuum tube having grid and plate electrodes, said grid being included in an input circuit of said amplifier tube and said plate in an output circuit thereof, capacity between said circuits including the natural capacity inherent between sad grid and plate electrodes, said circuits being traversed by currents of such high frequency as to make appreciable the capacity coupling between said circuits due to the said capacity and through which coupling high-frequency energy may be transferred to said antenna and radiated therefrom, an additional vacuum tube having an input circuit and an output circuit, said input circuit thereof being linked with said output circuit of said additional tube to facilitate the transfer of energy from said output circuit to said input circuit thereof for producing oscillations, and means associated with said radio-frequency amplifier tube for neutralizing the undesirable capacity coupling between the input and output circuits thereof, whereby said oscillations are in effect localized in said additional vacuum tube and thereby substantially prevented from being communicated to said antenna system.

2. In a radio receiver adapted to be connected to an antenna system, a radio-frequency amplifier including at least one vacuum tube having grid, plate and filament electrodes, said gr.d being included in an input circuit of said tube, and said plate in an output circuit thereof, capacity between said circuits including the natural capacity inherent between said grid and plate electrodes, said circuits being traversed by currents of such high frequency as to make appreciable the capacity coupling between said circuits due to the said capacity and through which coupling high-frequency energy may be transferred to said antenna and radiated therefrom, a vacuum tube detector having an input circuit and an output circuit, means for coupling the input circuit of said detector to the output circuit of a tube of said radiofrequency amplifier, means in the output circuit of said detector to facilitate the transfer of energy from the output circuit of said detector to the input circuit thereof whereby oscillations may be produced, and means including a capacity and a coil connected in series between the grid and the filament system of a tube of said radio-frequency amplifier for neutralizing the undesirable capacity coupling between the input and output circuits thereof, whereby said radio-frequency amplifier tube is rendered incapable of generating oscillations and whereby oscillations produced by said detector are in effect localized in said detector and thereby substantially prevented from being communicated to said antenna system.

3. In a radio receiver adapted to be connected to an antenna, a radio-frequency amplifier including a vacuum tube having grid and plate electrodes, an input circuit and an output circuit, inherent capacity including grid-plate capacity effectively connected between said circuits, said circuits being traversed by currents of such high frequency as to make appreciable the capacity coupling normally existing between said circuits due to said inherent capacity, and through which coupling high-frequency energy may be transferred to said antenna and radiated therefrom, a second vacuum tube having an input circuit and an output circuit, the input circuit of said second vacuum tube being coupled to an output circuit of said amplifier, means connected with said second vacuum tube to facilitate the transfer of energy from the output circuit to the input circuit thereof for producing oscillations, and means asso ciated with said radio-frequency amplifier for neutralizing said capacity coupling whereby said oscillations are in effect localized in said second vacuum tube and are thereby substantially prevented from being communicated to said antenna.

4. In a radio receiver adapted to be connected to an antenna system, a radio-frequency amplifier including a vacuum tube having an input circuit including a grid electrode and an output circuit including a plate electrode, inherent capacity including grid-plate capacity effectively connected between said circuits, said circuits being traversed by currents of such high frequency as to make appreciable the capacity coupling normally existing between said circuits due* to said inherent capacity, through which coupling high-frequency energy may be transferred to said antenna system and radiated therefrom and whereby said energy may cause voltage fluctuations to be impressed upon said grid electrode with the generation of resultant undesired oscillations by said radio-frequency amplifier tube, a second vacuum tube having an input circuit and an output circuit, the input circuit of said second vacuum tube being coupled to an output circuit of said amplifier, means connected with said second vacuum tube to facilitate the transfer of energy from the output circuit to the input circuit thereof whereby oscillations are produced, and means associated with said radio-frequency amplifier for neutralizing said capacity couplin whereby said amplifier is rendered incapa le of generating oscillations and whereby the oscillations generated b'y'said second vacuum tube are in effect localized in said second tube and. are thereby substantially prevented from being communicated to said antenna system.

5. In a radio signaling system including a vacuum tube capable of being placed alternatively in an oscillating and in a non-oscillating condition, a radio-frequency amplifier having an input circuit, an output circuit, and at least one vacuum tube coupled to said first-mentioned vacuum tube and adapted to relay radio-frequency signals thereto, inherent capacity between said input and output circuits, said circuits being traversed by currents of such high frequency as to make appreciable the capacity coupling normally ex isting between said circuits due to said inherent capacity, through which coupling high-frequency oscillations generated by said first-mentioned vacuum tube may be returned in a direction opposite to that in which said signals are relayed, and means associated with said radio-frequency amplifier for neutralizing said capacity coupling whereby said amplifier is adapted to transfer high-frequency energy substantially in one direction only, and consequently whereby said oscillations are in effect localized in said first-mentioned vacuum tube.

6. In a radio signaling system adapted to be connected to an antenna system, a detecting means alternatively operable as a nonoscillating detector and as a heterodyning detector, a radio-frequency vacuum tube amplifier having an input circuit including a grid electrode, and an out ut circuit including a late electrode, sai amplifier being couple between said antenna system and said detecting means, inherent capacity including grid-plate capacity between said input circuit and said output circuit, said cit"- cuits being traversed by currents of such high-frequency as to make appreciable the capacity coupling normally existing between said circuits due to said inherent capacity, through which coupling hi h-frefluency oscillations generated b said eteroyning detector may be trans erred to said antenna system and radiated therefrom, and means associated with said radio-frequency amplifying tube for neutralizing said capacity coupling, whereby said oscillations are in effect localized in said detecting means and are thereby substantially prevented from being communicated to said antenna system.

7. The combination in a radio-frequency signaling system of a vacuum tube arranged with a control grid and a cathode connected to an input portion for transferring signals through said cathode and an output electrode of said tube to an output system which includes a radio-frequency oscillatory source, of means preventing potential variations occurring between said output electrode and cathode from reacting upon said input portion, whereby oscillations of said source are in effect localized in said output system and thereby prevented from being communicated to said input portion.

8. The combination in a radio-frequency signaling system of a vacuum tube arranged with a control grid and a cathode connected to an input portion for transferring signals through said cathode and an output electrode of said tube to an output system which includes a radio-frequency oscillatory source, of means diverting from said input portion retroactive currents originating in succeeding portions of said system, whereby oscillation current of said source is effectively localized in said output system and prevented from being communicated to said input portion.

9. The combination in a radio-frequency signaling system adjustable selectively to receive signals throughout a range in frequency and including an input portion adapted for connection to an antenna, a vacuum tube having control grid and a cathode connected to said input portion, and an output electrode and said cathode connected to an output system which includes a radio-frequency oscillatory source, of means preventing potential variations occurring between said output electrode and cathode from reacting upon said input portion, whereby oscillations of said source are in efl'ect localized in said output system and thereby prevented from being communicated to said antenna.

10. The combination in a radio-frequency signaling system adjustable selectively to receive signals throughout a range in frequency and including an input portion adapted for connection to an antenna, a Vacuum tube having control grid and a cathode connected to said input portion, and an output electrode and said cathode connected to an output system which includes a radio-frequency oscillatory source, of means diverting from said input portion retroactive currents originating in succeeding portions of said system, whereby such portions are prevented from reacting upon said input portion, thereby to localize in said output system oscillations of said source and to prevent their being communicated to said antenna. 7

11. In a radio-frequency signal receiver, the combination of a vacuum tube having a control grid and an anode, an'input circuit connected to said grid and adapted to be connected with an antenna, an output system including a radio 4 frequency oscillation current source coupled to said anode and causing undesirable capacity currents to flow from said anode to other parts within said tube, and means substantially independent of frequency causing said capacity currents to flow back to said output circuit without traversing said input circuit, whereby oscillation current of said source is effectively localized in said output circuit and thereby prevented from being communicated to said antenna. 1

12. In a radio-frequency signal receiver, the combination of a vacuum tube'having a control grid and an anode, an in ut circuit connected to said grid and adapts to be connected with an antenna,'an out ut circuit including a radio-frequency oscil ation current source coupled to said anode and causing undesirable capacity currents to flow from said anode to other parts within said tube, and means independent of frequency diverting said capacity currents away from said input circuit, wherebyoscillation current of said source is efiectively localized in said output circuit and thereby prevented from being communicated to said antenna.

13. In a radio receiver, the combination with an antenna and a radio-frequency oscillato source, of a unidirectional repeater locate between said antenna and said oscillatory source for transferrin signals from said antenna thereto, said uniirectional repeat 3 er comprising the combination of a vacuum tube with means for preventing efiects upon the in ut circuit terminals of variations in potential across the output circuit terminals due to coupling otherwise present within said tube, and means for reducing incidental coupling between elements in the inputand output circuits of said tube.

14. In a radio receiver, the combination with an antenna and a radio-frequency oscillatory source, of a unidirectional amplifier stage com rising a vacuum tube having a control grid, cathode and anode, circuit elements providing an input and an output circuit for said stage, means coupling said input circuit to said antenna, means for tuning one of said circuits to resonance at a desired frequency, means preventing the varying potential of said output circuit from acting through coupling otherwise present within said tube from establishing variations of potential across said input circuit, and means for shielding the elements of said input and output circuits to prevent incidental couplings to and between the same. 4

15. The combination in a radio-frequencyv signaling system adjustable selectively to receive signals throughout a range in frequency and including an input portion adapted for connection to an antenna, a vacuum tube having a control grid and a cathode connected to said input portion, and an output electrode and said cathode connected to an output system which includes a radio-frequency oscillatory source, of means eliminating retroactive coupling between said output system and said antenna, whereby oscillations of .said source are efi'ectivel localized in said output system and there y prevented from being communicated to said antenna.

16. The combination in a radio-frequency signaling system of a vacuum tube arranged with a control grid and a cathode connected to an input circuit for transferring signals through said cathode and an anode of said tube to an output circuit which includes a radio-frequency oscillatory source, inherent capacity including grid-anode capacity effectively connected between said circuits, of'

means associated with said tube for neutralizing said capacity coupling, whereby oscillations of said source are effectively localized in said output circuit and thereby prevented from being communicated to said input circuit.

In testimony whereof I afiix my signature. LOU S A. HAZELTINE.

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