US2233566A - Elimination of power line interference in radio receiving hookups - Google Patents

Description

March 4, 1941. BQLE 2,233,566

ELIMINATION OF POWER LINE INTERFERENCE IN RADIO RECEIVING HOOKUPS Filed Nov. 16, 1938 2 Sheets-Sheet l ZZ navy/v5 J 25 22 2 v 0 O E z l4 z 2 J5 J9 I 25 26 Q I 2 20 I iii izza 7% BY W March 4; 1941.

ELIMINATION OF POWER LINE INTERFERENCE IN RADIO RECEIVING HOOKUPS Filed Nov. 16, I938 2 Sheets-Sheet 2 k W 7 H W BK g N Y! N N I I R m |!I\ w 5 w- 4 R R w kfi E v l 2 Q \fl i...

W M) [Q m w ---v R K s) Q 17 Ki Hhh 1 Jimaniar M F. E. BOLE 2,233,566

Patented Mar. 4, 1941 UNITED STATES PATENT OFFICE ELIMINATION OF POWER LINE IN TERFER- ENCE IN RADIO RECEIVING HOOKUPS Application November 16, 1938, Serial No. 240,895

11 Claims.

This invention relates to the elimination of power line interference in radio receiving hookups.

Over a period of years numerous attempts have been made to reduce and eliminate electrical interference experienced in the operation of radio receiving sets. Very little progress has been made in this direction because of the fact that the manner in which this trouble is transmitted to the receiving apparatus has not been fully appreciated. I have found that the greater proportion of this interference is set up in the power line of the receiving apparatus, and accordingly it is necessary to provide means which will eliminate this interference from the power line.

A difiiculty which exists is the fact that while one given means may eliminate the interference set up by one cause, it does not eliminate interference simultaneously set up from other causes.

It is an object of my invention to provide means for eliminating the interference from the power line of radio receiving apparatus which is so constituted that it can be set to eliminate interference arising from various different sources at the same time.

A still further object of the invention is to provide a simple type of device for the elimination of interference which may be varied in a simple manner to remove the various types of interference from various sources by a simple process of elimination.

With these and other objects in view, the invention consists in a unit which is connected in parallel with the power line and embodies various devices employed in a combination or combinations as selected to eliminate the various types of interference experienced at a given time, the unit including a switch member which may be: 40 operated to vary the combinations employed to suit the device to the conditions obtained at a given time.

The invention will be fully appreciated by reference to the following detailed specification taken in conjunction with the accompanying drawings.

In the drawings Figure 1 discloses a wiring diagram of the unit employing a series of switches in the various lines, selectively operable to connect or disconnect devices suppressing interference waves. Figure 2 is a diagrammatic view showing the character of the waves pro-- duced by one type of interfering electrical apparatus and the manner in which they are suppressed by a combination of devices employed in the unit. Figure 3 is a partly sectional view of a master switch control which may be employed to operate the unit. Figure 4 is a wiring diagram incorporating a control switch.

Referring to the drawings, Ill indicates one side of the power line and H the opposite side. In View of the fact that in modern power systems one side of the secondary distribution system is always grounded, it has been assumed for purposes of illustration, that line H is the grounded side of the circuit as is shown in drawings, Fig. l. The unit according to the present invention consists of a circuit or circuits connected in parallel with the power line by tapping in or otherwise connecting the leads [2 and I3. These circuits are so arranged as to offer a relatively low impedance to the current at the interfering frequency while at the same time preventing any appreciable loss of energy at the power frequency. Lead l2 incorporates an inductance coil M which by means of the connecting line It), resistance l6 and condenser ll connects lead l2 with lead It. Similarly lead I3 is connected through the inductance coil I8 and lead 89 incorporating the resistance 20 and condenser. H to lead 12. In the lines I 5 and I9, switches 22 and 23 respectively are included so that, as will later be explained, the associated coils, resistances and condensers may be connected in, or taken out of the various circuits in such combinations as may prove to be necessary under existing conditions. The lines l5 and I9 may be connected to the ground 24 in a selective manner, such as by the switches 25 and 26 which connect either side of the line with the ground lead 21. In the ground lead 27 by passing lines 28 and 29 may be incorporated, line 28 employing a switch 30 and line 29 incorporating a switch 3| and a condenser 32.

By means of various switches incorporated in the various lines as above referred to, it will be realized that many circuit combinations can be achieved. By way of example let it be assumed that interference is being set up in one side ID of the power line. Assuming that all the switches are open, switch 22 is closed so that current at the interfering frequency is passed through lead l2, inductance Hi, lead l5, resistance l6, and condenser H to the opposite side of the line, during which passage the interferingwaves are greatly reduced in strength due to attenuation and, in addition, the circuit acts as a Joy-pass, preventing the greater part of the interfering current from entering the receiving set. Assume that the interference is caused by an electrically operated razor, the interfering waves set up thereby being diagrammatically illustrated at A, Figure 2. The by-pass circuit consisting of the inductance coil l4, resistance l6 and condenser H, in series, has the effect of attenuating the interfering wave and at the same time by-passing the interfering current, so that less of the inter- 32 might sufficiently reduce the interfering waves so as to render them inaudible, depending of course upon the type of interference. This operation would increase the capacity in the circuit, due to the grounding of line I I, and the increased capacity might function to further reduce the interfering current to the point where the interference would be inaudible. In the case where the interference was arising on both sides of the power line, the closing of the switch 23 in addi tion to switch 22 would have the effect of passing the waves on side I l of the power line through the inductance [8, lead 13, resistance 20 and condenser 2I, and provide for a somewhat similar effect on that side of the line to that described in the case of side I0. In this instance switch 26 might be closed to ground line 19 through switch 3| and condenser 32. It will also be observed that when switches 26 and 3| are closed, condenser 32 will be in parallel with theseries arrangement of inductance l8 andthe inductance of one side of the power circuit as mentioned above, thus forming a parallel resonance circuit instead of increasing the capacity of condenser 2|.

It is pointed out that interference originating on one side of the power circuit, might be very different from interference coming from the opposite side and this would require different combinations of inductance, resistance and capacity for the two by-pass circuits. For instance, if the circuit required for side Hi, involved the inductance coil l4, resistance l6, and condenser I! alone, which combination was sufficient to eliminate the interference from that side of the line, then the connection for the other side of the line, that is line H, might require the condenser and ground connection through switches 26 and 3|, thus connecting condenser 32 in parallel with inductance l8 and resistance 20 together with the inductance of one side of the power circuit, as already explained.

It may be found that the combination of the inductance coil l4 and resistance 16 for instance, condenser 32 and ground 24 is all that is required in one side of the line to eliminate the interference being set up therein. In such a situation, switch 22 would remain open. In case the interference was originating on the grounded side of the line, the same procedure might not necessarily be followed, on account of the fact that the grounding of line H would place condenser 32 in parallel with inductance I8 and resistance 20 when switch 26 was closed. In such a case, switch 23 would be closed in place of switch 26, in order to reproduce conditions similar to those obtaining for line I when switches 25 and 3| are closed and switch 22 left open.

It will be appreciated therefore that the unit is of such character that by closing and opening the several switches employed in each lead, a different effect may be obtained on either side of the line, or similar effects may be produced in both sides of the line. Thus, by a process of elimination through the successive operation of the various switches referred to,'interference on both sides of the line may be eliminated.

It will be appreciated that resistances l6 and 20 connected in lines l and I9 are employed for the double purpose of dissipating energy from the interfering waves and to limit the current fiow in case of a breakdown of any of the condensers in the circuit.

The several switches above referred tomay be operated from a master control switch employing a sufficient number of contacts as to provide for setting up all the various combinations individually, that is one combination for each position of the master switch. For instance, referring to Figure 3 the master switch 33 is disclosed which may be constructed to employ a series of spaced apart axially aligned'annular members 34, which are insulated from one another and held rigidly. These members are provided each with an annular recess 35, on the ledge of which are carried a plurality of stationary contacts 36. Each one of these contacts on each member is designed to provide for the closing or opening of a switch in the unit. A rotary disc 31 is provided for each annular member fitting into the recess overlying the contacts 36, the discs being rigidly secured to the rotary shaft 38. Each disc carries a contact 39 which is designed to make.

contact with any one of the contacts 36 on the annular member with which each disc is associated, so that with each turn of the shaft 38 the contact on each disc 31 is caused to contact with an axially alignedcontact 36 on each an nular member 34. Consequently, assuming there were six annular members, six contacts are made along the length of the master switch, which may effect the closing of the majority of switches in the unit, or may effect the closing of but one or more. In this connection it will be appreciated that on some of the annular members 34 certain of the contact switches will not be connected,-so that the switch in the unit to which they would ordinarily correspond would then not be operated when such a contact was made.

The operation through the master switch is more aptly illustrated in Figure 5 where a practical Wiring diagram is illustrated and connected with the master switch which is shown diagrammatically, there being five annular members 34 with cooperating rotary discs 31, for the sake of simplicity. shown in the members 34, and contact 39 on each disc 31 is shown projecting from each disc for the sake of clarity, to make contact with the contacts 36. In this figure the contacts 39 are all engaging contact 36 of the members 34. From this it will be noted that the first element of the master switch which are numbered l to 5 connects inductance l8, resistance 20 and condenser 2I across the power line through the lead l2 to the side Hi. The second switch element connects inductance l4, resistance lfiand condenser ll through lead l3 to the opposite side ll of the power line. The action in connection with these two elements is the equivalent of closing switches 22 and 23. ,The third element connects ground 24 in the circuit and therefore func: tions to close switch 25. The fourth element of However, only four contacts are the switch also cuts in the ground 24 and therefore functions to close switch 26. The fifth element cuts in condenser 32 and ground 24, so it therefore functions to close switch 3|. As a result, therefore, all the elements in the unit function for the first position of the master switch.

On the second position of the master switch only one change takes place, it being clear that in the case of the elements I, 2, 3 and the same members of the unit are kept in circuit, whereas in the case of element 4 the contact 36 is neutral so that the resistance ground is eliminated from the circuit, which amounts tothe opening of the switch 28. Thus, inductance I8 is coupled across the line through the resistance 20 and condenser 2| to side It of the line, while inductance I4 not only is coupled across the line through condenser IT to side II, but is also connected to ground 24, via the condenser 32.

In the case of the third shift, the first element of the master switch does not function since the third contact is neutral. In view of this the condenser 2I is cut out of the circuit but the remaining elements of the switch connect exactly the same members in the unit as in the first shift, since element 4 of the switch through its third contact 36 functions to maintain ground 24 in the combination again. Thus, on. the third shift switch 23 of the unit is opened and the switch 26 is again closed. In this arrangement inductance I4, resistance I6 and condenser II are connected across the line, whereas inductance I8 is not connectedacross the line, but is grounded through switch 26, switch 3| and condenser 32. At the same time inductance I4 resistance It and condenser I1 is grounded through switch 26, switch 3i and condenser 32.

In the case of the fourth shift, element I of the master switch does not function, since the fourth contact is neutral. The same condition exists in element 2. Thus, both switches 22 and 23 are left open, eliminating the condensers II and 2| from the combination. However, element 3 includes in the combination with inductance I4, the ground 24, while element 4 includes the ground 24 with inductance I8. Element 5 cuts in the condenser 32. Thus, the circuit established connects both inductances I4 and I8, resistances I 6 and 29 to ground Via the condenser 32.

According to the wiring of the unit as shown, 31 combinations may be made so that 31 contacts would occur around each element 34. Thus,

' by continuing the rotation of the master switch through the various 31 positions, and having regard to the fact that the contacts may be neutral or connected, as is clear from the above illustration, wherein the master switch was rotated through four contacts, it will be appreciated that all the combinations it is desired to set up may be set up through one complete rotation of the master switch, stopping at each contact point through the complete rotation.

If desired, the positions of the master switch may be numbered or lettered, and having regard to the position to which the master switch may be rotated the operator can readily determine what combination is being employed for the immediate setting of the switch. It is therefore a very simple matter to set into operation whatever combination is required by selecting the position at which the switch should be set. Moreover, it is a very simple matter when interference is encountered to rotate the switch through its: successive positions and by a process of elimination set up those combinations which will eliminate the trouble. It is obvious, of course, that such a construction might be employed as a testing apparatus which might determine the cause of interference, having regard to the combination used to eliminate it, and the operator of the receiving apparatus furnished with an interference eliminating device which employs those combinations alone. In other words, it would be possible to manufacture units employing only one or a few of the combinations involved in the unit described, which would be employed to eliminate certain known causes of interference. This would obviate the necessity of a more expensive unit employing all the combinations, some of which would not be necessary in instances of this character.

In the case of some proposals in the past for eliminating interference, a measure of success has been achieved in eliminating noise caused by interference, the source of which is closely adjacent to the receiving apparatus. An important advance is made in the present development by reason of the fact that the unit will operate to eliminate interference, whether the device causing the interference is close to the receiver or located at any distance away. and having any effect on the receiver.

Various modifications may be made in this invention without departing from the spirit thereof or the scope of the claims, and therefore the exact forms shown are to be taken as illustrative only and not in a limiting sense, and it is desired that only such limitations shall be placed thereon as are disclosed in the prior art or are set forth in the accompanying claims.

I claim:

1. Apparatus for eliminating the transmission of power line interference to radio receiving sets comprising, in combination, a pair of parallel paths connected across said power line, each path including an inductance element, a resistance element, and a condenser connected in series, a third condenser having a connection from one terminal thereof to ground, and switching means for connecting the ungrounded terminal of said third condenser selectively to points on said parallel paths intermediate two of the elements in each path.

2. Apparatus for eliminating the transmission of power line interference to radio receiving sets comprising, in combination, a pair of parallel paths connected across said power line, each path including an inductance element and a condenser connected in series, the condensers in said paths being connected adjacent opposite sides of said line, a third condenser having a connection from one terminal thereof to ground, and switching means for connecting the ungrounded terminal of said third condenser selectively to intermediate points on said parallel paths.

3. Apparatus for eliminating the transmission of power line interference to radio receiving sets comprising, in combination, a pair of parallel paths connected across said power line, each path including an inductance element, a resistancei element, and a condenser connected in series, the condensers in said paths being connected adjacent opposite sides of said line, a third condenser having a connection from one terminal thereof to ground, and switching means for connecting the ungrounded terminal of said third condenser selectively to points on said parallel paths, said points being intermediate the in question might be condenser and the adjacent element in either of said parallel paths.

4. Apparatus for eliminating the transmission of power line interference to radio receiving sets comprising, in combination, a pair of circuit paths connected adjacent opposite sides of said line, and switching means for selectively completing and interrupting a bridging connection from a point in one of said paths intermediate two of the elements thereof to a point in the other of said paths intermediate two of the elements thereof.

5. Apparatus according to claim 4 and including a third condenser having a connection from one terminal thereof to ground, and switching means for connecting and disconnecting the ungrounded terminal of said third condenser to said bridging connection.

6. Apparatus for eliminating the transmission of power line interference to radio receiving sets comprising, in combination, a pair of circuit paths, each including an inductance element, a resistance element, and a condenser connected in series, switching means for selectively connecting and disconnecting said paths across said power line with the condenser elements of said paths connected adjacent opposite sides of said line, a third condenser having a connection from one terminal thereof to ground, and switching means for connecting the ungrounded terminal of said condenser selectively to points on said paths intermediate two of the elements in each path.

7. Apparatus for eliminating the transmission of power line interference to radio receiving sets comprising, in combination, a condenser, a switch for connecting said condenser to one side of said line, a resistance element and an inductance element connected in series with said condenser to the opposite side of said line, a second condenser and a second switch element for connecting the second condenser to the opposite side of the line, a second resistance element and a second inductance element connected in series with said second condenser to said one side of said line, a grounded circuit path including a condenser and a third switch element connected in series, and a pair of additional switch elements connecting the free end of said grounded circuit path respectively to intermediate points on the circuit paths of said first and second condensers.

8. Apparatus for eliminating the transmission of power line interference to radio receiving sets comprising, in combination, a condenser, a switch for connecting said condenser to one side of said line, a resistance element and an inductance element connected in series with said condenser to the opposite side of said line, a second condenser and a second switch element for connecting the second condenser to the opposite side of the line, a second resistance element and a second inductance element connected in series with said second condenser to said one side of said line, a third condenser having one terminal thereof connected to ground, and two additional switch elements for connecting the ungrounded terminal of said third condenser selectively to points on the circuit paths of said first and second condensers, said points being intermediate two of the elements in each path,

v9. Apparatus according to claim 7 wherein said switch elements are formed. as rotar; switch elements, each having a plurality of positions for closing or opening the switch element, and including a common control element for simultaneously operating the rotary parts of said switch elements, whereby different circuit combinations are established in different positions.

of said common control element. v

10. Apparatus according to claim 8 wherein said switch elements are each provided with a movable part having a plurality of positions for closing or opening the switch element, and including a common control element for simultaneously operating the movable parts of said switch elements, whereby different circuit combinations are established in different positions of said control element.

11. Interference eliminating means for wireless receivers comprising a, pair of adjustable filters connected across the supply lines for said receiver, each filter consisting of an inductance, a capacity and a resistance connected in series,

the order of the elements being reversed in each filter whereby the path through the filters from each line will lead through the inductance in one filter and through the capacity in the other, switches in each of the filters between the capacity and the line, a grounded capacity, switches adapted to connect the grounded capacity in series or in parallel across each filter and a master controller for operating said switches and adapted when operated to form a succession of alternative connections varying the inductance and capacity of the filters.

FLOYD EDWIN BOLE.

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