445,968

PATENT SPECIFICATION

Application Date: Aug. 17, 1934. No. 23793/34.

Complete Specification Left: April 18, 1935.

Complete Specification Accepted: April 17, 1936.

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PROVISIONAL SPECIFICATION

Improvements in or relating to Aerial Systems

We, EDWARD CECIL CORK, a British Subject, of 50A, Kenilworth Road, Ealing, London, W.5, ALAN DOWER BLUMLEIN, a British Subject, of 7, Courtfield Gardens, Ealing, London, W.13, and ERIC LAWRENCE CASLING WHITE, a British Subject, of 32, The Rise, Hillingdon, Middlesex, do hereby declare the nature of this invention to be as follows:-

The present invention relates to aerial systems.

In short wave reception an aerial is often connected to a receiver by means of a feeder which may comprise one insulated conductor and one conductor earthed at one or More points along its length. The feeder often comprises a conductor arranged centrally of and insulated from an earthed sheath.

In many cases it is required to receiver short and long wave signals simultaneously. For example, it may be desired to receive television signals on a short wavelength and the accompanying sound on a medium or long wavelength. Hitherto it has been necessary to employ two aerials for this purpose.

It is an object of the present invention to enable long or medium wave signals to be received simultaneously with short wave signals, without the provision of a separate aerial.

According to the present invention an aerial system comprises a feeder having two conductors, for example a conductor surrounded by a sheath, the feeder being associated at one end with a short wave aerial and at the other end having one conductor, for example the sheath, connected to earth or to the earth point of receiving apparatus through a series tuned circuit tunable to a short wavelength, whereby this conductor is effectively earthed at a short wavelength and effectively insulated from earth at a longer wavelength.

The invention further provides a short wave receiving aerial coupled to a feeder consisting of at least two conductors which are arranged to transmit the short wave signals to the receiver in phase opposition on the two conductors, the conductors being insulated from earth and being adapted to operate in parallel and in like phase as aerial and lead in for medium or long waves be connection to a suitable receiver.

According to a feature of the present invention a wireless receiver adapted, when associated with a short wave aerial connected to a feeder having two conductors, such as a conductor surrounded by a sheath, for simultaneous reception of relatively short and relatively long wave signals, comprises two tuned circuits one tunable to each carrier frequency to be received and each circuit being coupled to apparatus responsive to the signals to which the circuit is tuned, means for coupling the feeder to the receiver in such a manner that one conductor, for example the central conductor, is associated as aerial with the circuit tunable to the shorter wavelengths and the other conductor, for example the sheath, is associated as aerial with the circuit tunable to the longer wavelengths and means whereby the second mentioned conductor is effectively earthed at the shorter wavelengths and effectively insulated from earth at the longer wavelengths.

In order that the invention may be more readily understood, an application thereof to the reception of television signals on a short wavelength, simultaneously with the accompanying sound signals on a medium wavelength, will be described by way of example.

The first valve of a short wave wireless receiver has a parallel tuned circuit, tunable to a short wavelength and comprising an inductance in parallel with a variable condenser, connected between its control grid and the earthed metal chassis of the receiver. The cathode of the valve is connected to the chassis through a bias resistance shunted by a decoupling condenser.

The first valve of a medium wave receiver is mounted on the same chassis and has a parallel tuned circuit, tunable to a medium wavelength and comprising an inductance in parallel with a variable condenser, connected between its grid and the chassis. The cathode of this valve is also connected to the chassis through a bias resistance shunted by a decoupling condenser.

A feeder comprising a conductor arranged centrally within a cylindrical sheath is associated at one end with a short wave aerial. The other end of the feeder projects through an aperture in the receiver chassis. The central conductor is connected through a coupling condenser of small capacity to a tapping on the inductance in the short wave parallel tuned circuit.

The sheath of the feeder is connected to a tapping on the inductance in the longer wave parallel tuned circuit and is also connected to the chassis through a series tuned circuit, tunable to a short wavelength and comprising an inductance in series with a variable condenser. No direct connection exists between the sheath and either the chassis or earth.

Both the series and the parallel short wave circuits are tuned to the frequency of the carrier of television signals to be received. The series tuned circuit has a low impedance at its resonant frequency and the coupling condenser between the central conductor and the tapping on the inductance in the short wave parallel tuned circuit has a low impedance to signals at short wavelengths. At the short wavelength to which the circuits are tuned the sheath is therefore effectively earthed through the series tuned circuit and the central conductor is connected through a connection of low impedance to the tapping on the inductance in the short wave parallel tuned circuit and therefore signals of this wavelength appearing across the receiver end of the feeder are passed, with little attenuation, to the parallel tuned circuit and thence to the first valve of the short wave section of the receiver.

At frequencies corresponding to medium or long wavelengths the impedance of the series tuned circuit approximates to that of the condenser in this circuit and is high because this condenser is of low capacity. The sheath is therefore effectively insulated from earth for these waves. The sheath thus acts as an aerial and signals appearing between the lower end of the sheath and earth are applied across a part of the inductance of the medium wave tuned circuit, which circuit is tuned to the frequency of the carrier of the sound signals. The required signals therefore appear across the tune circuit and are applied to the first valve of the medium wave section of the receiver.

The two valves are either themselves arranged to detect the incoming signals or are associated with suitable detectors in known manner and the modulations, after suitable amplification, are fed to suitable signal responsive devices. Thus the television signals may be fed to a picture reproducer, such as a cathode ray tube, and the sound signals may be fed to a loudspeaker.

The coupling condenser is inserted in the lead between the central conductor and the tapping on the inductance in the short wave parallel tuned circuit in order to increase the impedance between the central conductor and earth at the lower carrier frequency. Were this condenser omitted the capacity between the two elements of the feeder would effectively earth the outer conductor at the lower frequency, since the impedance between the tapping point on the short wave inductance and earth is small at this frequency.

Although a particular arrangement of the invention has been described in its field of application to television reception the invention is limited neither to this arrangement nor to this field of application. Many other arrangements and applications of the invention will be apparent to those versed in the art. For example, the condenser coupling between the feeder and the short wave section of the receiver may be replaced by transformer coupling. In this case the inductance in the short wave parallel tuned circuit may act as the secondary winding of a transformer the primary of which is a coil connected between the two members of the feeder.

The invention is also applicable to short wave aerials not using a concentric feeder. For example, it is sometimes arranged that the short wave aerial is connected to one of a pair of wires acting as a feeder. The other wire (not connected to the aerial), is usually earthed and acts as a "counterpoise" to prevent signals being picked up by the feeder. Such a system may be used according to this invention by insulating and connection the counterpoise in the manner suggested for the sheath of the concentric feeder.

Similarly, the invention may be applied to a balanced short wave feeder. Such a feeder may consist of two wires connected in symmetrical fashion to a short wave aerial and running adjacently to a receiver where they are connected to the primary of a short wave transformer feeding the signals to the receiver. With such an arrangement according to this invention, the centre point of the transformer primary, instead of being connected to earth of chassis, may be connected to a medium or long wave receiver. For medium or long waves the two conductors then operate in parallel as an aerial. If desired, the centre point of the transformer primary may be held at earth potential for short waves by means of a series tuned circuit.

Dated this 15th day of August, 1934.

REDDIE & GROSE,

Agents for the Applicants,

6, Breamís Buildings, London, E.C.4.

COMPLETE SPECIFICATION

Improvements in or relating to Aerial Systems

We, EDWARD CECIL CORK, a British Subject, of 50A, Kenilworth Road, Ealing, London, W.5, ALAN DOWER BLUMLEIN, a British Subject, of 7, Courtfield Gardens, Ealing, London, W.13, and ERIC LAWRENCE CASLING WHITE, a British Subject of 32, The Rise, Hillingdon, Middlesex, do hereby declare the nature of this invention and in what manner the same is to be performed, to be particularly described and ascertained in and by the following statement:-

The present invention relates to aerial systems.

In short wave reception an aerial is often connected to a receiver by means of a feeder which may comprise one insulated conductor and one conductor earthed at one or more points along its length. The feeder often comprises a conductor arranged centrally of and insulated from an earthed sheath.

In many cases it is required to receive short and long wave signals simultaneously. For example, it may be desired to receive television signals on a short wavelength and the accompanying sound on a medium or long wavelength. Hitherto it has been necessary to employ two aerials for this purpose.

It is an object of the present invention to enable long or medium wave signals to be received simultaneously with short wave signals, without the provision of a separate aerial.

In Patent Specification No. 424,239 which was not published at the date of the present application but bears an earlier date, there is described and claimed a radio receiving system for short wave and long wave signals, comprising signal pick up means, a pair of downlead conductors, means for causing a rise or fall in potential in said pick up means due to long wave signals to produce a potential rise in one downlead conductor and a simultaneous potential fall in the other downlead conductor, and means for transferring to said downleads potential differences between electrically spaced points in said pick up means due to short wave signals, whereby circulating longwave signal currents and circulating short wave signal currents are produced in said downleads. In this system no part of the short wave feeder operates as a long wave aerial.

According to the present invention there is provided a wireless receiving system comprising a short wave aerial and a feeder having a conductor surrounded by a conductive sheath, the feeder being associated, at one end, with the short wave aerial and, at the other end, with two receiving circuits, one for operation at relatively short wavelengths and the other for operation at longer wavelengths, the system being characterised in that the sheath is connected at the latter end with a circuit whereby the sheath is effectively earthed at said short wavelengths and effectively insulated from earth at said longer wavelengths, the arrangement being such that, in operation, the feeder serves to feed signals from the short wave aerial to the short wave receiving circuit and, simultaneously, the sheath acts as an aerial for signals of said longer wavelengths which are fed to the longer wave receiving circuit.

According to a feature of the present invention there is provided a wireless receiving system comprising a short wave aerial and a feeder having two conductors, the feeder being associated, at one end, with the short wave aerial and, at the other end, with two receiving circuits, one for operation at relatively short wavelengths and the other for operation at longer wavelengths, the system being characterised in that the two conductors are connected to the two ends of the short wave receiving circuit and in that the centre point of the receiving circuit is connected with a circuit whereby said centre point is effectively earthed at the short wave lengths and effectively insulated from earth at the longer wavelengths, the arrangement being such that short wave signals are transferred to the short wave receiving circuit substantially in phase opposition along the two conductors and that simultaneously the feeder, or a part thereof, serves as an aerial for longer wavelength signals which are fed thereby to the longer wave receiving circuit.

The invention will be described by way of example with reference to the accompanying diagrammatic drawings, wherein

Fig. 1 shows an arrangement according to the present invention,

Fig. 2 shows a modification of Fig. 1,

Fig. 3 shows a further arrangement according to the invention,

Fig. 4 shows a modification of Fig. 3 and

Figs. 5 and 6 show modifications of parts of Fig. 4.

Referring to Fig. 1 of the drawing, the first valve 1 of a short wave wireless receiver has a parallel tuned circuit, tunable to a short wavelength and comprising an inductance 2 in parallel with a variable condenser 3, connected between its control grid 4 and the earthed metal chassis 5 of the receiver. The cathode 6 of valve 1 is connected to the chassis 5 through a bias resistance 7 shunted by a decoupling condenser 8.

The first valve 9 of a medium wave receiver is mounted on the same chassis 5 and has a parallel tuned circuit, tunable to a medium wavelength and comprising an inductance 10 in parallel with a variable condenser 11, connected between its grid 12 and the chassis 5. The cathode 13 of valve 9 is also connected to the chassis through a bias resistance 14 shunted by decoupling condenser 15.

A feeder 16 comprising a conductor 17 arranged centrally within a cylindrical sheath 18 is associated at one end with a short wave aerial (not shown). The other end of the feeder projects through and aperture 19 in the receiver chassis 5. The central conductor 17 is connected through a coupling condenser 20 of small capacity to a tapping point 21 on the inductance 2 in the short wave parallel tuned circuit 2, 3.

The sheath 18 of feeder 16 is connected to a tapping point 22 on the inductance 10 in the longer wave parallel tuned circuit 10, 11 and is also connected to the chassis 5 through a series tuned circuit, tunable to a short wavelength and comprising an inductance 23 in series with a variable condenser 24. No direct connection exists between the sheath 18 and either the chassis 5 or earth.

Both the series shortwave circuit 23, 24 and the parallel short wave circuit 2, 3 are tuned to the frequency of the carrier of television signals to be received. The series tuned circuit 23, 24 has a low impedance at its resonant frequency and the coupling condenser 20 between the central conductor 17 and the tapping point 21 on the inductance 2 in the short wave parallel tuned circuit 2, 3 has a low impedance to signals at short wavelengths. At the short wavelength to which the circuits 2, 3 and 23, 24 are tuned the sheath 18 is therefore effectively earthed through the series tuned circuit 2, 3, and the central conductor is connected through a connection of low impedance to the tapping point 21 on the inductance 2 in the short wave parallel tuned circuit 2, 3 and therefore signals of this wavelength appearing across the receiver end of the feeder are passed, with little attenuation, to the parallel tuned short wave receiving circuit 2, 3 and thence to the first valve 1 of the short wave section of the receiver.

At frequencies corresponding to medium or long wavelengths the impedance of the series tuned circuit 23, 24 approximates to that of the condenser 24 in this circuit and is high because this condenser is of low capacity. The sheath 18 is therefore effectively insulate from earth for this wave. The sheath 18 thus acts as an aerial and signals appearing between the lower end of the sheath and earth are applied across a part of the inductance 10 of the medium wave receiving circuit 10, 11 which circuit is tuned to the frequency of the carrier of the sound signals. The required signals therefore appear across the tuned circuit 10, 11 and are applied to the grid 12 of the first valve 9 of the medium wave section of the receiver.

The two valves 1, 9 are either themselves arranged to detect the incoming signals or are associated with suitable detectors (not shown) in known manner and the modulations, after suitable amplification, are fed to suitable signal responsive devices. Thus the television signals may be fed to a picture reproducer, such as a cathode ray tube, and the sound signals may be fed to a loudspeaker.

The coupling condenser 20 is inserted in the lead between the central conductor 17 and the tapping point 21 on the inductance 2 in the short wave parallel tuned circuit 2, 3 in order to increase the impedance between the central conductor 17 and earth at the lower carrier frequency. Were condenser 20 omitted that capacity between the two elements 17, 18 of the feeder 16 would effectively earth the outer conductor 18 at the lower frequency, since the impedance between the tapping point 21 on the short wave inductance 2 and earth is small at this frequency.

In Fig. 2, transformer coupling is employed between the feeder 16 and the short wave parallel tuned receiving circuit 2, 3 of the short wave section of the receiver. Condenser 20 of Fig. 1 is omitted and a coil 25 is connected between the ends of the conductors 17, 18 of feeder 16. Coil 25 is arranged to constitute the primary winding of a transformer 26 of which inductance 20 constitutes the secondary winding. In other respects Fig. 2 is similar to Fig. 1, like references being used to denote like parts.

In some cases it may be inconvenient for the medium or long wave aerial to terminate at the receiver. For example, the receiver may be situated at a point subject to electrical interference from neighbouring electrical apparatus. In such a case an aerial terminating at the receiver is liable to pick up interference which will mar reception. It is then desirable to arrange that the aerial is located at a point which is remote from the receiver and which is not subject to electrical interference, the aerial being connected to the receiver by a screened feeder.

One arrangement whereby this result can be obtained is illustrated in Fig. 3. A short wave aerial 27 is connected to one end of a concentric feeder 28 comprising a central conductor 29 and a sheath 30. The other end of feeder 28 terminates within a coupling device arranged within an earthed metal box 31. This sheath 30 is insulated from the box 31 but is effectively connected thereto at the short wavelength to be received by means of a series resonant circuit 32, 33 tuned to this wavelength. A transformer 34 serves to coupled feeder 28 to another concentric feeder 35, the sheath 3 of which is earthed and the central conductor 37 being connected at one end to transformer 34 and at the other end to tapping point 21 to inductance 2 f the short wave receiver. The primary windings 38, 39 of two step-down transformer 40, 41 are connected at one end to earth and at the other end through condensers 42, 43 to the sheath 30 of feeder 28. The secondary winding 44, 45 of transformers 40, 41 are connected in series, their common point being connected to earth through a condenser 46. The free ends of secondary windings 44, 45 are connected to two conductors 47, 48 of a further feeder 49 which is provided with an earthed sheath 50. Feeder 49 is coupled at its other end to the input of the medium or long wave receiver, conductors 47 and 48 being connected to the primary windings 51, 52 (arranged in series) of two step-up input transformers 53, 54. The common point of the primary windings 51, 52 is earthed through a condenser 55 and the secondary windings 56, 57 of transformers 53, 54 are connected in series and between earth and tapping point 22 on inductance 10.

In this arrangement short wave signals are picked up by aerial 27, fed through feeder 28, the sheath of which is effectively earthed at these high frequencies by the series resonant circuit 32, 33, transferred by transformer 34 to feeder 35 and thereby passed on to the input circuit of the short wave receiver. Sheath 30 of feeder 28 is effectively insulated from earth for medium and long wavelengths and therefore sheath 30 and aerial 27 together form a medium or long wavelength aerial. Signals picked up by this aerial are passed by one of the transformers 40, 41 to feeder 49, and thence through one of transformers 53, 54 to the input circuit of the longer wave receiver. It is preferably arranged that one transformer of each of the pairs of transformers 40, 41 and 53, 54 to the input circuit of the longer wave receiver. It is preferably arranged that one transformer of each of the pairs of transformers 40, 41 and 53, 54 is operative over one wave band (e.g. 250 to 600 metres) the other two transformers being operative over another wave band (e.g. 1000 to 2000 metres). If it is only desired to operate over one of these wave bands one transformer at each end of feeder 49 may be removed. In this case only a single core is required in feeder 49.

It will be seen that, by suitably locating the box 31 and by providing suitable lengths of feeders 35 and 49 to connect it to the receiver, both the short wave aerial 27 and the long wave aerial 27, 30 may be remote from the receiver and may therefore be arranged so that they avoid local electrical interference.

Fig. 4 shows a modification of Fig. 3. In the case of Fig. 4 only a single concentric feeder is used to connect the box 31 to the two receivers. Transformers 40, 41, 53, 54, the associated condensers 42, 43, 46, 55, and feeder 49 of Fig. 3 are not employed in the arrangement of Fig. 4. In this case neither end of the secondary winding of transformer 34 is directly connected to box 31 but one end is effectively earthed at the operating short wavelength through a series tuned circuit 58, 59. The common point of this tuned circuit and the secondary winding of transformer 34 is connected to the tapping point 60 of a step-down auto-transformer 61 connected between sheath 30 and earth.

In the receiver, the primary winding 62 of a short wave transformer, of which inductance 2 forms the secondary winding, and a further short wave series tuned circuit 63, 64 are connected in series between conductor 37 and earth. The common point of series circuit 63, 64 and winding 62 is connected to tapping point 22 on inductance 10 of the medium or long wave receiver.

It will be seen that with this arrangement the two sets of signals are fed in series to feeder 35, and at the receiver end of this feeder the signals excite their respective receiving circuits.

In a modification shown in Fig. 5 of the box 31 of Fig. 4, transformer 34 and series circuit 58, 59 are replaced by a condenser 65 coupling conductor 29 to conductor 37 and a short wave parallel tuned circuit 66, 67 connected between conductor 37 and tapping point 60 of auto-transformer 61. In this case the two sets of signals are fed in parallel to feeder 35, the high impedance of the parallel tuned circuit 66, 67 at the operating short wavelength serving to prevent transfer of currents of this frequency between conductor 37 and auto-transformer 61. At the longer wavelength the impedance of this circuit is low and it serves to feed current from auto-transformer 61 to conductor 37.

An arrangement similar to that of Fig. 5 may be employed for separating the signals at the receiver, this arrangement being shown in Fig. 6 in which conductor 37 is connected through a condenser 68 to tapping point 21 on inductance 2 of the short wave receiving circuit, and also, through a parallel circuit 69, 70 tuned to the operating short wavelength, to tapping point 22 on inductance 10 of the long wave receiving circuit.

Although particular arrangements of the invention have been described with reference to television reception the invention is limited neither to these arrangements nor to television reception. Many other arrangements and applications of the invention will be apparent to those versed in the art.

The invention may also be applied to a balance short wave feeder. Such a feeder may consist of two wires connected in symmetrical fashion to a short wave aerial and running alongside of one another to a receiver where they are connected to the primary of a short wave transformer acting as short wave receiving circuit feeding the signals to the short wave receiver. With such an arrangement according to this invention, the centre point of the transformer primary, instead of being directly connected to earth, may be connected to a physical earth or the chassis, which is equivalent, through a circuit such as a series resonant circuit tuned to the short wave length. The centre point of the transformer primary is also connected to a medium or long wave receiving circuit. For medium or long waves the two conductors then operate in parallel as an aerial.

Having now particularly described and ascertained the nature of our said invention and in what manner the same is to be performed, we declare that what we claim is:-

  1. A wireless receiving system comprising a short wave aerial and a feeder having a conductor surrounded by a conductive sheath, the feeder being associated, at one end, with the short wave aerial and, at the other end, with two receiving circuits, one for operation at relatively short wavelengths and the other for operation at longer wavelengths, the system being characterised in that the sheath is connected at the latter end with a circuit whereby the sheath is effectively earthed at said short wavelengths and effectively insulated from earth at said longer wavelengths, the arrangement being such that, in operation, the feeder serves to feed signals from the short wave aerial to the short wave receiving circuit and, simultaneously, the sheath acts as an aerial for signals of said longer wavelengths which are fed to the longer wave receiving circuit.
  2. A wireless receiving system according to claim 1, wherein said circuit whereby the sheath is effectively earthed at said short wavelength comprises a series resonant circuit tuned to said short wavelength.
  3. A wireless receiving system according to claim 1 or 2, wherein the whole of said feeder is located remote from said receiving circuits and wherein there are provided means including one or more further feeders for coupling the first named feeder to said receiving circuits.
  4. A wireless receiving system according to claim 3 in which only one further feeder is employed, wherein there are provided means for causing said further feeder to operate as a feeder for both the short and the longer wave signals.
  5. A wireless receiving system comprising a short wave aerial and a feeder having two conductors, the feeder being associated, at one end, with the short wave aerial and, at the other end, with two receiving circuits, one for operation at relatively short wavelengths and the other for operation at longer wavelengths, the system being characterised in that the two conductors are connected to the two ends of the short wave receiving circuit and in that the centre point of the receiving circuit is connected with a circuit whereby said centre point is effectively earthed at the short wave-lengths and effectively insulated from earth at the longer wavelengths, the arrangement being such that the short wave signals are transferred to the short wave receiving circuit substantially in phase opposition along the two conductors and that simultaneously the feeder, or a part thereof, serves as an aerial for longer wavelength signals which are fed thereby to the longer wave receiving circuit.
  6. A wireless receiving system substantially as described with reference to Figs. 1 of 5 of the accompanying drawing.

Dated this 18th day of April, 1935.

REDDIE & GROSE,

Agents for the Applicants,

6, Breamís Buildings, London, E.C.4.

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Leamington Spa: Printed for His Majestyís Stationery Office, by the Courier Press. Ė 1936.