US2061736A - Radio receiver - Google Patents

Description

Nov. 24, 1936. I M, A. MCLENNAN 2,061,736,

RADIO RECEIVER Filed June 25, 1932 INVENTOR Miles .l lcLennan HIS ATTORNEI Patented Nov. 24, 1936 UNITED STATES PATENT OFFIE 7 Claims.

My invention relates to radio receivers and, more particularly, to receivers of the so-called remote control type.

It is an object of my invention to provide a light, portable tuning or station selecting unit capable of being moved from place to place in a living room, or a similar location, in order that accurate tuning of a radio receiver may be accomplished from any desired point therein.

Another object of my invention is to provide a remote control radio receiver so constructed that the portions thereof not involved in the tuning operation may be disposed at a distance from the tuning unit proper Without militating against the efficiency of the system considered as a Whole.

A still further and more specific object of my invention is to provide, in a radio receiver of the type preferred to, a single manually operable element that shall function both as a volume control and as an on-oif switch.

In brief, a receiving system embodying my invention preferably comprises three separate units, namely, (1), a tuning-control unit including a signal receptor, such as a loop antenna, an oscillator, a first detector, (2) a main amplifier and 7 power supply device, and (3) a loudspeaker. The tuning unit preferably is enclosed in a small box about 10"x5"x6", and the tuning condensers therein are interconnected for uni-control. The pickup loop is mounted inside the tuning control cabinet and, for ordinary signal reception, need not be over 5" square.

It is, of course, feasible to dispose the tuningcontrol unit adjacent to a lead-in from an outside antenna, if desirable, but I have found that very satisfactory reception may be had using only the loop in the control unit.

The main amplifier I, preferably, dispose in the basement of the house wherein the installation is made and I connect it to the tuning unit through a five-wire cable, which cable not only supplies power for the operation of the three tubes in the tuning unit but also conveys the intermediate frequency signal from the tuning unit to the amplifier.

The constants of the cable are so chosen, i. e., the inductance and distributed capacity thereof, that, together with an input coil disposed in the main amplifier, the said cable provides maximum transmission efiiciency for the intermediate frequency.

The intermediate frequency portion of the main amplifier is a completely shielded unit, preferably utilizing thermionic tubes of the scree grid type, such as those commercially known as UX222, and operates at a frequency of about 160 kilocycles. The audio frequency amplifier portion and the power unit are orthodox in substantially all respects, as is also the dynamic itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best be understood from the accompanying drawing, the single figure of which is a diagrammatic view of a complete radio receiving system constructed and arranged according to my invention.

Referring to the drawing, a radio receiving system constructed according to a preferred embodiment of my invention comprises a portable tuning control unit indicated by a dotted line I, a'portable loudspeaker 3 disposed within soundrange of the said unit, and a remotely situated amplifier and power supply device indicated by a dotted rectangle 5. In the drawing, the remote location of the amplifier and power supply unit as, for example, in the basement of a dwelling house or the like wherein the system is installed, is indicated by a partition or fioor l, and by the fact that portions of the conductors interconnecting the several elements are shown in dotted lines.

The portable tuning control unit includes a frequency converting tube, or first detector, 9, an oscillator tube ll, an intermediate amplifier tube l3, and a signal receptor such as a small loop IS. The tuning condensers l1 and I9, respectively, associated with the first detector and the oscillator, are preferably of the straight line frequency type and are interconnected for simultaneous actuation.

The several thermionic tubes 9, H, and I3 may be inter-connected for signal transfer purposes in any manner well known to those skilled in the art, although I have found by experience that the connections shown in the drawing offer certain advantages. For example, it will be noted that the locally generated oscillations are impressed on the plate circuit of the frequency converting tube through a conductor 2| leading to the low potential end of a beat-frequency output circuit constituted by a choke coil 23 and a condenser 25, this particular mode of connection being somewhat advantageous in that it, to some extent, minimizes the deleterious effect upon the tuning of the radio frequency stage occasioned by the tuning of the oscillator, and also tends to minimize radiation of the locally generated oscillations.

A choke coil 26 is preferably interposed in the plate potential supply connection to the first detector tube 9, the constants of this coil being so chosen that it offers a high impedance to the 10- cally generated oscillations from the oscillator tube H.

The tubes in the tuning control unit are supplied with cathode heating potentials over a plurality of common conductors 27 and 29, of which the conductor 29 extends to the positive pole of a battery 3| disposed in the amplifier unit 5, the connection including the winding of a relay 33, While the other conductor, 21, extends from the cathodes to a fixed contact 35 of a switching de vice 3'1, mounted in the remote control unit. The switching device includes a resilient contact arm 39 from which a conductor 49 extends to the negative pole of the battery.

The switching device, it will be noted, in addition to the contacts included in the cathode heating circuit, also comprises a potentiometer constituted by a resistor 4! and a movable contact 43. The upper end of the resistor is connected to the plate of the first detector [3 through a condenser 45. When the movable contact 43 is in the position shown in the drawing, the oathode heating circuit of the several tubes in the system is broken and, at the same time, since the movable contact is connected conductively to the cathode of the first detector, the potentials impressed upon the input circuit of the beat frequency amplifying portion of the main amplifier are minimum.

The main amplifier includes a plurality of beat frequency amplifier tubes 47, 49, and 5i, a second detector tube 53, and a plurality of audio frequency amplifier tubes 55 and 57, the tube 51 being of the power type, and the tubes 4'! and 49, as well as 49 and 5!, being connected through similar tuned impedance networks 59. The first or input tube of the beat frequency amplifier is coupled to the output circuit of the tube l3 over the common conductor 21 and a conductor 6|, the latter extending between the plate of amplifier tube l3 and the high potential end of an impedance device 63. The constants of the cable including the several conductors thus far enumerated and the impedance device are so chosen that attenuation of the beat frequency is minimum.

The detector tube 53 may be coupled in any desired manner to the third beat frequency amplifier tube 55, and the audio frequency amplifier tubes 55 and 51 may be connected by a transformer 65, the first of these tubes being coupled to the output circuit of the detector in any desired manner, as by a network El. The specific coupling network 67 shown in the drawing, and which I have found quite satisfactory, includes a series resonant circuit 59 tuned to the beat frequency, a coupling resistor H, a blocking condenser 13, and an audio frequency choke coil l5. This increases the efficiency of rectification and, at the same time, does not attenuate the high audio frequencies such as does a simple by-pass capacitor as heretofore known.

Grid bias potential for the second detector 53 and the first audio frequency amplifier 55 may be provided by a small biasing battery 11, the positive terminal of which is adjustably connected to a resistor 19 disposed across the cathode heating current supply leads 2'! and 29. The manner in which bias potential is applied to the grid of the power amplifier tube will be hereinafter referred to in more detail.

In order that the battery 3| supplying cathode heating potentials to all of the tubes in the system with the exception of the power amplifier may be kept charged I, preferably, provide a full wave rectifier 9i and float the battery across the output terminals thereof. The rectifier is supplied with high potential alternating current from a power transformer 83, one terminal of the primary winding of which is directly connected to a power line, and the other terminal of which, over an adjustable resistor 81, may be connected to the remaining power supply line over a circuit including a plurality of contacts 89 and 9i, carried by the armature of the relay 33 interposed in the cathode heating circuit.

Plate potentials for all of the tubes in the system are supplied from a rectifier 93 energized from a power transformer 95, the primary winding of which is connected in parallel with the primary winding of the transformer which feeds the battery charging rectifier. The rectifier 93 has an output circuit serially including a choke coil 81, the field winding 99 of the loudspeaker 3, and an output resistor IOI, one end of which is connected to the negative terminal of the rectifier 93 and, preferably, is provided with a ground connection.

The power transformer includes an additional secondary winding I03 for the purpose of supplying cathode potential to the power amplifier 57, a resistor I05 being connected across this winding, and having a mid tap from which a connection l0! extends to the negative terminal of the rectifier output resistor I01 over a biassupply resistor I09.

Upon reference to the drawing, it will be noted that the space current flowing in the power amplifier tube 51 returns to the negative end of the rectifier output resistor over a path including the resistor Q05 connected across the cathode heating winding )3 and the resistor I09 connected between the said winding and. the negative end of the rectifier output resistor IDI. It will also be noted that the grid of the power amplifier tube is connected to the grounded negative end of the rectifier output resistor l9! over a circuit including the conductors 21, and 40, and, therefore, is maintained at a potential negative with respect to the cathode by reason of the drop across the resistor I99.

In order that the operation of my improved receiving system may be clearly understood, let it be assumed that the on-off switch 3"! in the tuning control unit is in the position shown in the drawing. Such being the case, the cathode heating circuits of all of the tubes except the power amplifier are interrupted and the relay 33 is not energized. If, now, the movable contact device 43 is adjusted away from the position shown in the drawing in the direction indicated by the arrow, the contacts 35 and 39 of the switch are permitted to close. The closing of these contacts supplies potential to the oathodes of the tubes over the conductors 2'! and 40 and, simultaneously therewith, the relay 33 is energized, causing the contacts 89 and 9| to close. The closing of the relay contacts completes a circuit through which the primary windings of the several power transformers 83 and 95 75 are connected to the power supply lines and the rectifiers 93 and BI deliver, respectively, plate current to the tubes in the system and charging current for the cathode heating battery 3|.

Obviously, the secondary winding IE3 of the transformer 95, at the same time, supplies cathode potential to the power amplifier tube 5'! and the entire system is in condition for the reception of signals.

During signal reception, the tuning control unit i may be moved from place to place without militating against signal reception, the range of movement of the device being circumscribed only by the length of the cable interposed between it and the point at which the said cable enters the room wherein the unit is disposed.

The loudspeaker 3 also may be moved to any convenient location determined by the length of the cable connecting it to the output circuit of the main amplifier.

For volume control purposes, the movable element 43 of the on-off switch 31 is moved further and further toward the free end of the resistor 4| associated therewith, such movement serving to increase the volume and movement in the reverse direction serving to reduce the volume.

It will, accordingly, be appreciated from a consideration of the foregoing description of a preferred embodiment of my invention that a system constructed in accordance therewith offers many advantages. For example, my improved system lends itself admirably to installation in dwelling houses where the living room is too small to accommodate a radio receiver of the usual console type. Furthermore, by reason of the mobility of the tuning control unit, it may be placed in any convenient location in the said living room such, for example, as adjacent to the favorite armchair of the householder and, from that position, the control of signal reception may be had with minimum effort. Many other advantages will be apparent to those skilled in the art to which my invention pertains.

Although I have chosen a preferred embodiment of my invention for purposes of illustration, it is to be clearly understood that I am not restricted thereto, my invention being limited only by the extent of the prior art and by the spirit of the appended claims.

I claim as my invention:

1. A radio receiver of the superheterodyne type comprising a portable tuning unit including means for converting an incoming signal into an amplified intermediate frequency signal, a remotely disposed second detector for converting the intermediate frequency signal to an audio frequency signal, means including a cable for transferring said intermediate frequency signal from said portable unit to said remotely disposed second detector, and means for utilizing said audio frequency signal.

2. The invention set forth in claim 1 characterized in that the portable unit includes an oscillator, a first detector and at least one stage of a beat frequency amplifier.

3. The invention set forth in claim 1 characterized in that the portable unit includes at least one stage of a beat frequency amplifier in addition to said signal converting means, and that said cable has suitable constants for minimizing the attenuation of intermediate frequency signals transferred thereover.

4. A radio receiver of the superheterodyne type, comprising a portable tuning unit including means for converting an incoming signal into an intermediate frequency signal and amplifying said last named signal, a remotely disposed intermediate frequency amplifier, second detector,

audio frequency amplifier and power supply device, a multi-conductor cable having suitable constants for minimizing the attenuation of intermediate frequency signalling currents conductively connecting said unit and said second detector, and a loudspeaker connected to said amplifier and power supply device to receive energizing potentials therefrom.

5. In a radio receiving system of the superheterodyne type, a radio frequency amplifier, oscillator and first detector comprised within a portable housing, an intermediate frequency amplifier, second detector, audio frequency amplifier and power supply device comprised within a remote housing, a sound reproducing unit connected to said audio frequency amplifier and power supply device, and means including conductive connections between said portable housing and said remote housing for minimizing the attenuation of intermediate frequency currents which are transferred from said first detector to said intermediate frequency amplifier.

6. In a superheterodyne receiving system, a portable unit containing a tuning unit, frequency converter and intermediate frequency amplifier, a remotely situated unit containing a further intermediate frequency amplifier, second detector, audio frequency amplifier, and power supply device; a multi-conductor transmission cable conductively connecting said portable unit with said remotely situated unit; and a sound reproducer connected to said audio frequency amplifier; the electrical constants of the conductors in said transmission cable being such as to minimize the attenuation of intermediate frequency currents traversing a certain pairof said conductors there in, and the tuning unit and frequency converter being adapted to effect suitable interaction between a desired incoming signal and local oscillations for producing signalling currents of a given intermediate frequency band, whereby said currents may be transmitted to said remotely situated unit for deriving audio frequency currents to be impressed upon said sound reproducer.

7. A remote control superheterodyne receiver comprising, in combination, a unitary control device including frequency converting and amplifying elements, an amplifier for the conversion frequency, further means for amplifying said conversion frequency remotely located with respect to said control device, means for transmitting amplified conversion frequency signals from said device to said last named means, a signal detector connected with said further amplifying means to derive the modulation signal therefrom, a modulation signal amplifier and sound output device for reproducing the output from said signal detector, power supply means for said receiver connected with said control device, said amplifiers and said sound producing device to energize the same, and means in said control device for operating said power supply means to energize said receiver.

MILES A. MoLENNAN.

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