US2243182A - All wave radio receiving system - Google Patents

Description

y 9 Ejv. AMY ETAL 2,243,132

ALL WAVE RADIO RECEIVING SYSTEM Filed Dec. 19, 1954 2 Sheets-Sheet 1 INVENTORS flea/57 M AMY BY JUL/U5 6. lab-v56 May 27, 1941. E. v. AMY ET AL ALL WAVE RADIO RECEIVING SYSTEM 2 Sheets-Sheet 2 Filed Dec. 19, 1934 INVENTOR5 ERA/57" M AMY BY adj/4125 G. fizz-v5.5

ATTORNEY.

RECEIVER Patented May 27, 1941 ALL WAVE RABIG RECEIVENG SYSTEM York Application December 19, 1934, Serial No. 758,234

22 Claims.

This invention relates to radio receiving apparatus and more particularly to antenna systems and arrangements for supplying a radio receiver with actuating or signal voltage, maintaining the highest ratio of signal voltage to interference or noise voltage.

It is an object of our invention to provide a simplified antenna system which may be utilized with so-called all Wave receivers to provide a maximum of signal voltage for the desired signal, which may be any frequency of a Wide band of frequencies, whether that be such as the socalled broadcast or so-called short waves or both, with a minimum of interference.

It is a further object of our invention to proide an antenna system in which the antenna may operate as a simple T antenna (as hereafter defined) or as a doublet or di-pole antenna, without requiring the use of switching apparatus, or may operate as an antenna having characteristic in between the characteristics of a T antenna and a doublet, and in which either characteristic may be caused to predominate as desired.

It is a further object of our invention to provide an antenna system of the class described in which interference, and particularly manmade static, may be easily and quickly balanced out, without substantially affecting the signal voltage supplied to the receiver.

It is a further object of our invention to provide a doublet antenna system, the effective length of which is automatically varied without adjustment in accordance with the incoming signal.

Still other objects and advantages of our invention will be apparent from the specification. The features of novelty which we believe to be characteristic of our invention are set forth with particularity in the appended claims. Our invention itself, however, both as to its fundamental principles, and as to its particular embodiments, will best be understood by reference to the specification and accompanying drawings, in which Fig. l is a schematic circuit diagram illustra ing the fundamental principles of our invention;

Fig. 2 shows a modified form thereof;

Figs. 3 and 4 still further modifications thereof;

Fig. 5 a simple and for some purposes preferred embodiment;

Fig. 6 represents a still further modification of our system; and

Fig. 7 is a circuit diagram of one form of doublet in accordance with our invention having different effective lengths for different frequencies.

In accordance with one aspect of our invention we utilize an antenna system which is preferably in the form of an unsymmetrical doublet or a di-pole antenna connected to the radio receiver through a double conductor lead-in directly connected across the gap in the doublet and through a special balancing transformer to the radio receiver and to ground. The windings of the transformer are preferably of the same number of turns and coupled with a very close coupling and one winding is connected in series with each conductor of the lead-in and the two windings are connected together and through a path, which may contain resistance, to ground, or the ground terminal of the receiver.

Signals which cause the antenna to resonate as a doublet will produce circulating currents; that is to say, currents flowing down in one of the twisted pair down-leads and one of the transformer windings and up in the other at the same instant, as indicated by the full line arrows of Fig. 1. If the antenna and ground terminal of the receiver be connected across one of the windings of the transformer or to a third winding coupled thereto, such circulating currents will produce a maximum voltage across the input of the receiver for true doublet action. However, any disturbances which affect both halves of the antenna or down-leads alike and in phase, such for instance as local interference, will not produce circulating currents flowing in the opposite direction at the same instant in the down-leads, but will produce currents flowing in the same direction at the same instant, as indicated by the dotted arrows in Fig. l, and these currents, by reason of the tight coupling be tween the two transformer windings, will substantialiy neutralize the resultant magnetic field from the two halves of the winding and produce no induced noise voltage in the radio receiver.

If resistance be introduced between the common point of the transformer windings and the connection to the ground terminal of radio receiver, it will be apparent that the greater the resistance, the more nearly the antenna system approaches in performance an exposed capacity connected to the antenna terminal of the receiver, for convenience called a T antenna, and the less it resembles true doublet action. It should be noted also that the doublet is selective as to frequency, and responds as a doublet at a maximum when its length is one-half the wave length of the incoming signal, although the frequency response is not sharp or critical.

Thus it will be seen that by varying the magnitude of the resistance from maximum to minimum or zero, the antenna system can be caused to function first as a substantially pure T antenna, or as a substantially pure doublet, permitting advantage to be taken of the doublet characteristic when the desired frequency is such as to produce strong doublet response, and of the T response for frequencies where doublet action is not required; or by selecting intermediate values of the resistance, it is possible to obtain characteristics of both, it being understood that the lower the resistance the more nearly the antenna will function as a true doublet (providing the signal frequency lies within the doublet response range), and the higher the resistance the more nearly it will function as a T antenna or simple capacity exposure.

Our invention also comprehends the balancing or neutralization of interference picked up by the antenna against that picked up by the lead-in. For instance, we may utilize in the connection to the receiver various means for controlling the phase and magnitude of the interference voltage picked up by the lead-in so that it may be balanced against that picked up by the antenna to cancel or minimize the total interference alfecting the receiver, in addition to providin the means hereinbefore provided for converting the antenna from doublet to T action.

Referring now more particularly to Fig. 1, l and 2 designate the two halves of a doublet, the inner ends 3 and 4 of which (separated by a small gap either electrically or physically) are connected to the upper terminals of a double lead-in made up of a pair of electrically symmetrical conductors. number of forms; for instance, it may be an ordinary twisted pair lead-in made up of conductors 5 and 6 insulated from each other but twisted This lead-in may take a together throughout their length. It may also be a pair of conductors intimately associated although untwisted, as for instance, an ordinary lamp cord, or it may be separate conductors spaced apart a predetermined distance and periodically transposed; but for convenience we have referred to it throughout as a twisted pair lead-in. The lower terminals of the twisted pair are connected respectively to the terminals of coils 1 and 8 of a transformer having a common point B.

If desired, there may be associated with the windings I and 8 a third winding 9 acting as the secondary of a transformer and preferably having a larger number of turns than coil 1 or 8 to provide an effective step-up to coil 9. One terminal of the winding 9 may be connected to the common point 0, the other terminal to the input terminal M of a radio receiver, and condenser Hl may be connected between the upper terminal of coils 8 and 9. The point ii is preferably connected to the ground terminal of the receiver and there may be interposed in the said connection a variable inductancell variable resistance 12 and variable condenser I3. The ground terminal of the receiver I 5 may or may not be connected directly to ground, as may be found to operate best by trial. Inany event, in the case of a receiver operated from the house lighting circuit, the receiver is usually effectively grounded through the house lighting circuit, either directly or through a capacity.

The operation of the system indicated in Fig. 1 is as follows. It will be assumed that the desired signals produce circulating currents in the coils l and 8. In the simplest case these circulating currents may be assumed to be due to the pure doublet action and may be assumed at a given instant to produce currents flowing down through conductor 6 and up through conductor 5. These circulating currents, however, may be produced in other ways, as at frequencies to which the doublet response is small or zero, as for instance by the use of a special transformer having one winding reversed with respect to the other Where the antenna length is small in comparison with the wave length, as set forth in our patent Re. 19,854, issued February 18, 1936, or they may be produced by the use of asymmetrical antenna branches in which the difference in effective length of the two branches will produce a differential current in the transmission line and thereby effectively produce circulating currents.

These circulating currents are indicated by the full line arrows and it will be understood that they are intended to represent only the current picked up by the antenna and which comprises the desired signal and a certain amount of interference, which may also be picked up by the antenna, and the magnitude of which may vary considerably.

The passage of the circulating currents through the coils l and 8, as will be understood, induces in the secondary coil 9. a voltage representing both signal and interference (assuming that some interference has been picked up by the antenna).

When the lead-in is unshielded, it also will pick up interference, and this interference may be considerably greater in magnitude than that picked up by the antenna, but in any event, at any given instant the currents due to such interference picked up by the lead-in will be in the same direction as indicated by the dotted arrows and, since the windings 1 and 8 are balanced and tightly coupled, the voltage induced in coil 9 due to such interference currents will be substantially zero. These interference currents may be considered as traveling to point 0 where they combine and pass through inductance ll, resistance I2 and capacity l3 to ground terminal l5, producing voltage drops across coil H, resistance l2 and condenser I3.

The voltage effective across the input circuit of the receiver will be the vectorial sum of the voltage produced in coil 9 due to circulating currents of both signal and interference, and that produced in coil H, resistance l2 and condenser l3.

By adjustment of the values of inductance H, resistance 12 and condenser l3, it will be apparent that both the magnitude and the phase of the interference voltage can be adjusted so as to oppose and substantially cancel out the interference voltage developed in coil 9 due to the action of the antenna itself.

It will be clear that if the signal and the interference come from the same direction and from a reasonably long distance from the antenna or under other conditions where there will be substantially the same field distribution of in terference and signal in the surrounding medium of both the antenna and the downleads, the cancellation of the interference by the method above described would also entail cancellation of the signal. For interference developed in the immediate neighborhood, however, the ratio of interference picked up by the lead-in to that picked up by the antenna is very much smaller than the corresponding :ratio for signals, and therefore the signal voltages will be out of balance while the interference voltage may be substantially completely cancelled, producing a considerable increase in signal to interference ratio, with only a slight loss of signal strength.

In most cases the amount of interference which the antenna itself picks up is small compared to that which is picked up by the lead-in, and hence the loss of signal strength due to the method just described is small wherever the antenna is located in a field which is strong in signal energy and weak in interference energy.

The advantages of this method are considerable, particularly when the antenna is somewhat directional and consequently further discrimination'in favor of the signal against interference is secured. The almost complete exclusion of the interference, even at the expense of a slight loss in signal strength, will permit the use of the full gain of the receiver which would otherwise be limited or prevented by the amplification of interference.

A second method of balancing the interference picked up by the antenna against that picked up by the lead-in is illustrated in Fig. 2, where, instead of changing the phase of the balancing voltage by means of an impedance containing inductance, resistance and capacity, the effective length of the transmission line or lead-in is varied so that the phase of the voltage across the secondary winding is adjusted with respect to the phase of the drop across the resistance. In this instance, we have indicated an asymmetrical doublet consisting of portions 20 and 21 of different lengths and, as before, the twisted pair lead-in comprises conductors 5 .and 6 connected at points 3 and 4.

In this instance, the lower terminals of the lead-in are connected to wave coils 22 and 23 which are connected together through a resistance 24 equal to the surge impedance of the line, including the wave coils 22 and 23.

Coils I and 8 are provided as before, connected together at point 0, and the opposite terminal of each coil is connected to a suitable point on wave coils 22 and 23. The secondary 9 is connected to point .0 and through resistance 12 to the ground terminal of the receiver. In this instance, by adjusting the effective length of the transmission line, that is, by adjusting the taps on coils 22 and 23, it is possible to make the transmission line ofan effective length such that phase opposition may take place in several frequencies close to those channels which are most commonly received, in which case a commercially satisfactory balance may be obtained merely by varying the magnitude of resistance l2. In other cases, it will be found that a partial balance is satisfactory and experience has shown that resistance alone can reduce interference to an appreciable degree, even in frequencies widely separated from each other, as for example at 6 and i8 megacycles.

Under certain circumstances the secondary winding 9 of the transformer may be omitted; for example, in Fig. 3 the antenna terminal of the receiver may be connected directly to one end of the coils 'l or 8 and the cormnon point to the ground terminal l of the receiver through variable inductance l l capacity 13 and resistance 12.

Referring now more particularly to Fig. 4, which is generally similar to Fig.2, we have indicated the omission of the secondary 9, in this instance the antenna terminal of the receiver being connected to one end of coil I and the common point 0 being connected through resistance 1 2 to the ground terminal I 5, and the outside terminals of coils 'I' and 8 being connected to sliders on conductors 5 and 6. This arrangement is particularly well adapted for so-called ultra short waves in which the inductance of leads 5 and 6 may be substantial in effect. 7

Asymmetry and circulating currents for frequencies which do not produce true doublet response may be obtained not only by unequal lengths of the branches of the doublet antenna, but also by electrically shortening one of the branches by means of resonant circuits or by inductance or capacity inserted in series in either branch. For instance, in Fig. 6 we have shown 7 the insertion of inductance 30 and condenser 3| forming either a parallel tuned circuit or a series tuned circuit (not shown )in series in the branch 2! of an asymmetrical doublet, the effect of which is to make one of the branches quite dissimilar to the other one for a narrow band of frequencies. It will be understood that a number of such circuits tuned to desired frequencies may be introduced into either one or both branches at difierent geographical points in such a manner as to obtain maximum signal strength for the favorite channel or channels.

Under certain conditions and particularly for locations in which interference is relatively low and signals strong, it may be desired to eliminate the feature of balancing interference picked up by the antenna against that picked up by. the leadin. For this purpose we prefer to utilize the arrangement shown in Fig. 5, which is the simplest and most economical. In this instance we have shown an asymmetrical doublet antenna comprising portions l and 2 connected to lead-in conductors 5 and 6, the lower terminals of which are connected to coils l and 8; the common point 83 is connected through variable resistance l2 to the ground terminal E5; the antenna terminal being connected to the upper terminal of coil 8.

Coils l and 8 are always reversed with respect to each other in any suitable manner to be hereafter described.

When resistance I2 is entirely out out by adjustment, substantially pure double-t action is obtained at or over a considerable frequency band, as already described. For instance, with an asymmetrical doublet having one branch 5 feet and the other feet long, satisfactory doublet reception is obtained from meters to 5 meters. Interference picked up on the lead-in only, produces equal and opposite currents in windings 7 and 8 with substantial neutralization thereof, the neutralization being dependent, among other things, on the degree of coupling between the coils I and 8, loosening the coupling decreasing the efficiency of neutralization.

If it be found that there is little or no interference it will be desired to utilize the antenna as a T antenna to obtain all the signal voltage possible. In order to do this the resistance [2 is set at its maximum value, as a result of which the entire antenna and lead-in system then acts as a T antenna or capacity exposure, and the voltage developed across the receiver input terminals is increased by the voltage through resistance !2.

In operating the system shown in Fig.5 in different levels of interference at diiferent times, it will be found that by adjusting the resistance l2 to the proper point it will be possible to find an adjustment providing the best signal to in terference ratio. In general, the greater the interference the lower value of resistance will be utilized in the circuit and the less the interfer- 5 ence the more resistance. We have found that a resistance which may be continuously increased from zero to a maximum of about 1000 ohms is very satisfactory for the purpose and enables a quick and accurate adjustment for maximum signal to interference ratio, and little benefit is obtained by increasing the resistance above this value.

In general, coils 1 and 8 may be formed in a number of ways, the direction of winding and pcling being so chosen that currents in the same direction in the down-lead tend to neutralize or cancel each other, as in a plain helical coil tapped at its midpoint to form point 0, and having its opposite terminals connected to the lower ends of leads 5 and 6. Such a coil, however, in general, will not have suflicient coupling between its halves, and the coupling is preferably .increased in any of the known ways, as by winding the two coils I and 8 as a bifilar winding, or the like, or with several wires in hand, and then connecting in the proper direction, since the neutralization of interference is, in general, improved as the coupling approaches unity, and in practice, the coupling should be made as near unity as possible.

It is diflicult to lay down invariable rules. for adjustment of the apparatus because much depends upon the particular conditions in which the receiver is operating and the station which it is desired to receive. For instance, ordinarily with relatively nearby stations when little interference is being picked up, an increase in signal strength without a corresponding increase in interference may be generally obtained by increasing the resistance l2 above zero. Yet we have found that under certain conditions just the reverse action obtains and the resistance should' be kept at or close to zero. For instance, in testing We have found that at approximately the same time in receiving a far distant station the best signal-to-static ratio was obtained by reducing the resistance to zero, thereby eliminating the lead-in pick-up, while on a closely adjacent frequency receiving from a relatively near 0 by station for best results it was necessary to introduce some resistance and utilize the lead-in pick-up to some extent.

While we do not wish to be bound to any particular theory of operation, we believe that in the case of the distant station there was 'substantially no ground wave and that the reception was due practically entirely to sky waves being reflected downward from the Heaviside layer at a very sharp angle, under which conditions only the fiat portion of the antenna would be affected. Under such conditions the lead-in picks up substantially no signal and its only pickup can be interference. Best results under these conditions are obtained by keeping the resistance at a minimum. On the other hand, in the case of a relatively nearby station where a substantial ground wave is being received and where there is no high angle reflection from the Heaviside layer, there is a substantial pick-up by the lead-in which may be utilized to advantage and this requires that a certain amount of resistance be introduced.

At any rate, whatever the explanation may be 70 we wish to note the fact that the circuit in Fig. 5 has proved to be extremely effective under many conditions and that no matter what the conditions may be, it is always possible by adjustment of the resistance to obtain optimum reception. As previously stated, substantially no benefit is obtained by increasing the maximum value of the resistance above -1000 ohms. It is desirable that this resistance be continuously variable in ad justment; that is, it should vary in smooth and imperceptible amounts rather than in definite steps, for the reasons that one never knows at what particular value of resistance the balance will be found, this being dependent upon many variable factors, as already explained. It is also desirable that the resistance be arranged to produce a logarithmic or exponential variation rather than a linear variation for equal movements of the adjustment knob. For instance, if the knob has a motion of 180, the resistance may vary from 0 to 10 ohms in the first 60, 10 to in the next 60", and 100 to 1000 in the last 60.

Since adjustable resistances so arranged are obtainable upon the open market and since the detailed construction by which such an adjustment is obtained forms per se no part of our invention, the same has not been shown or described in detail.

Referring now more particularly to Fig. 7, We have shown a form of doublet which is, so to speak, automatically tuned for the particular frequency to be received, 1. e., is so arranged that the incoming signal of predetermined frequency excites the particular length of the doublet which is most effective for that frequency. In this instance l and 2, as before, represent the two branches of the doublet. Assuming that it is desired to receive on this antenna signals in the 5 meter channel and 10 meter channel, at a point four feet out from the gap, the antenna is cut and the coil 32 interposed. This coil has its constants so chosen as to act as a choke for 5 meter waves. It will therefore be understood that only the first four feet of the antenna out from the gap will respond to signals of 5 meters and this length is the proper length for such signals.

To enable a greater length of the antenna to respond to lower frequencies, condenser 33 may be interposed, which is so chosen as to substantially neutralize the effect of coil 32 at the next desired frequency, for example, the 10 meter channel. We may proceed, in likemanner, for a greater number of frequencies, by electrically limiting the length of each branch of the doublet to the most effective value for the reception of each narrow band of favorite frequencies or wave lengths. This may be accomplished by the insertion of parallel tuned rejectors, such as the one shown in Fig. 6. All frequencies except those in the narrow :band for which the rejector has a high impedance, will pass without substantial change in amplitude, but those within the band will be substantially blocked, thereby limiting electrically the effective length of the doublet for optimum signal pick-up.

It will be understood that in the case of a symmetrical doublet the same will be done to both branches of the doublet as indicated by the inclusion of coil 39 and condenser 40 at 10 meters.

It will be noted that in this arrangement the doublet is symmetrical for 5 meters and also 10 meters, since the same lengths are effective in each branch. i

In this connection it is usually desirable to mount the associated coil and condenser within a conducting container at which, however, is insulated from the antenna and from the enclosed coil and condenser.

If desired the coils and condensers may be interposed in only one branch of the doublet, thus rendering it completely asymmetrical and it will be undertsood that this antenna system may be used with any of the systems already shown and described.

It will be understood that the foregoing systems are not limited to the operation of a single radio receiver from an antenna, but the same may be used where more than one receiver is cperated from :a single antenna.

Subject matter not claimed in this application is embodied and being claimed in one or more copending applications for patent.

While we have shown and described certain preferred embodiments of our invention it will be understood that modifications and changes may be made without departing from the spirit and scope thereof, as will be understood by those skilled in the art.

We claim:

1. In a radio receiving system, in combination, a doublet antenna, a pair of tightly coupled interference neutralizing coils having a common terminal, a pair of electrically symmetrical conductors hating their upper ends connected across the gap in said doublet and having their lower ends connected to the terminals of said pair of neutralizing coils, a connection from one of said coils to the antenna terminal of a radio receiver, and a connection from the said common terminal to ground, said connection including a series condenser.

2. The combination claimed in claim 1 in which said last mentioned condenser is replaced by a resistance.

3. The combination claimed in claim 1 in which said last mentioned condenser is replaced by a resistance variable between zero and 1080 ohms.

4. In a radio receiving system, in combination, a doublet antenna, a pair of tightly coupled interference neutralizing coils having a common terminal, a pair of electrically symmetrical conductors having their upper ends connected across the gap in said doublet and having their lower ends connected to the terminals of said pair of tightly coupled neutralizing coils, a radio receiver, means for producing a potential difference across the input terminals of said radio receiver due to circulating currents, a connection between said common terminal and the ground post of said radio receiver, and adjustable means for impressing upon the input of said receiver any desired amount of incoming signal picked up by said lead-in conductors.

5. The combination claimed in claim i, in which said last mentioned means comprises apparatus for adjusting the phase and magnitude of the signal energy picked up by said lead-in conductors.

6. The combination claimed in claim 1 in which the last mentioned connection includes another impedance means.

7. In a radio receiving system for the reception of long and short waves, in combination, a doublet antenna, a pair of conductors having their upper ends connected to the portions of said doublet, a transformer having a primary winding connected to the lower ends of said conductors and a secondary winding, a connection from said secondary to the input circuit of a radio receiver, and a connection from said secondary to ground, the latter connection including adjustable interference neutralizing means in series circuit between said secondary winding and the ground terminal of said receiver.

8. In a radio receiving system for the reception of long and short waves, in combination, a doublet antenna, a pair of conductors having their upper ends connected to the portions of said doublet, energy transfer means connected to the lower ends of said conductors, a connection from said energy transfer means to the input circuit of a radio receiver, and a connection from said means to ground, the latter connection including means for adjusting the phase or magnitude of an undesired portion of the energy picked up by said antenna and conductors.

9. In a radio receiving system, in combination, a doublet antenna, a pair of conductors having their upper ends connected to the portions of said doublet, energy transfer means connected to the lower ends of said conductors, a connection from said energy transfer means to the input circuit of a radio receiver, and a connection from said means to ground, the latter connection including a capacity and "an inductance which are adjustable to choose a portion of the energy picked up by said conductors and vary the phase and. magnitude thereof to balance out undesired energy picked up by said iconductors.

10. In a radio receiving system, in combination, a'doublet antenna, a pair of conductors having their upper ends connected to the portions of said doublet, adjustable wave changing means in circuit with said conductors, energy transfer means connected to the lower ends of said conductors, a connection from said energy transfer means to the antenna terminal of a ductors having their upper ends connected to the portions of said doublet, means for causing said doublet and said lead-in conductors to act also as a capacity exposure, energy transfer means connected to the lower ends of saidconductors, a connection from said energy transfer means to the antenna terminal of a radio receiver, and a connection from said energy transfer means to the ground terminal of the radio receiver, the latter connection including interference neutralizing means.

12. In a radio receiving system, in combination, a doublet antenna, a pair of conductors having their upper ends connected to the portions of said doublet, energy transfer means connected to the lower ends of said conductors, a connection from said energy transfer means to the input circuit of a radio receiver, and adjustable means for causing said doublet and said lead-in conductors to act as a capacity exposure and for intermediately adjusting the degree to which the doublet operates as a capacity exposure.

13. In a radio receiving system, in combination, a doublet antenna, a pair of conductors having their upper ends connected to the portions of said doublet, energy transfer means connected to the lower ends of said conductors, a connection from said energy transfer means to the antenna terminal of a radio receiver, means for converting the antenna system from action as a doublet to act as a capacity exposure, and a connection from said energy transfer means to the ground terminal of the radio receiver, the latter connection including a capacity and an inductance which are adapted to choose a portion of the energy picked up by said conductors and vary the phase and magnitude thereof.

14. In a radio receving system, in combination, an antenna having at least a pair of spaced arms, a pair of conductors having their upper ends connected to said arms, a primary winding of a transformer connected to said conductors, a connection therefrom to the ground post of a radio receiver, said connection including an inductance, means connected between said primary and the antenna post of said radio receiver, and a step-up transformer secondary connected to both of said antenna and ground connections.

15. In a radio receiving system, in combination, a doublet antenna, a pair of conductors having their upper ends connected to said doublet, a step-up transformer comprising a primary having a pair of coils connected to said conductors and a secondary connected to the primary and to the antenna post of a radio receiver, and a connection from said coils to the ground post of said radio receiver, said connection including a condenser.

16. In a radio receiving system, in combination, a doublet antenna, a pair of conductors having their upper ends connected to said doublet, a step-up transformer comprising a primary having a pair of coils connected to said conductors and a secondary connected to the input circuit of a radio receiver, a condenser connected between a conductor and the receiver input, and a connection from said coils to the ground post of the radio receiver, said connection including an inductance and a condenser.

1'7. In a radio receiving system, in combination, a doublet antenna, a pair of conductors having their upper ends connected to said doublet, a step-up transformer comprising a primary having a pair of coils connected to said conductors and a secondary connected to the input circuit of a radio receiver, a condenser connected between a conductor and the receiver input, and a connection from said coils to the ground post of the radio receiver, said connection including impedance means.

18. A radio receiving system for the reception of long and short wave signals by a radio receiver having provision for antenna and ground terminals, said system comprising an antenna having at least two portions; a pair of conductors connected to said portions, a transformer adjacent the receiver and having a primary winding connected to said conductors and a secondary winding connected to the input circuit of said radio receiver; a connection form said secondary to said ground terminal; a conductive connection from the primary to the input circuit for the passage of signals, and impedance means permanently connected in said circuit between the primary and the receiver input circuit for the passage of short wave signals.

19. In a radio receiving system, in combination, an antenna having at least a pair of spaced arms, a pair of conductors hving their upper ends connected to said arms, means responsive to the impressed signal from the antenna and arranged to pass long and short wave signals to a radio receiver and comprising inductive connections between said conductors and the input circuit of the radio receiver, a conductive connection including a condenser between said conductors and the same receiver input, and a connection from said means to ground.

20. A radio receiving system adapted for the reception of long and short wave signals by a radio receiver having provision for antenna and ground connections, said system comprising an antenna having at least two portions; a pair of down-lead conductors having their upper ends connected to said portions; a transformer having a primary winding connected to the lower ends of said conductors and a secondary winding connected to the antenna and ground connections of said radio receiver; and impedance means connected in circuit between said conductors and to said antenna connection, the system acting automatically so that both the signal voltage between the portions of the antenna and that bewteen the antenna, its down-leads and ground are supplied simultaneously to the antenna connection of the receiver where either or both voltages may be selected in accordance with the short, intermediate or long wave operation of the receiver.

21. In a radio receiving system, in combination, an antenna of the dipole type having at least a pair of spaced arms, means connecting said arms comprising a. pair of down-lead conductors joined to said arms respectively and a transformer primary winding connected between said conductors, a radio receiver having antenna and ground terminals, a connection from an intermediate point on said primary winding to said ground terminal, said connection containing an inductance and a condenser, a connection from said antenna terminal to said ground terminal, saidconnection containing a secondary winding for said transformer and said inductance and condenser.

22. In a radio receiving system, in combination, an antenna having at least a pair of spaced arms, a pair of conductors having their upper ends connected to said arms, a step-up transformer connected to said conductors and to a radio receiver having an antenna post, the circuit including said transformer being arranged to pass signals of long wave length to the receiver, and a fixed conductive circuit between the transformer and the antenna post of the radio receiver including a capacitance and being arranged. to pass short wave signals to the same receiver.

ERNEST V. AMY. JULIUS G. ACEVES

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