USRE23651E - Radio receiver - Google Patents

Description

May 5, 1953 R. R. FLoRAc Re. 23,651

RADIO RECEIVER Original Filed July 29, 1950 I ATTORNEY Reiuued May 5,- 1953 RADIo RECEIVER f 1 Richard R. Florac, New York, N. Y., assignor, by

mesne assignments, to Aircall, Inc., New York, N. Y., a corporation ot Delaware Original No. 2,619,589, dated November 25, 1952, Serial No. 176,747, July 2 9, 1950. Application for reissue December 29, 1952, Serial No. 328,539

(ci. 25u- 20) Matter enclosed in heavy brackets I: appears in the original patent but forms no part o! 8 Claims.

This invention relates to portable radio receivers, and more particularly to high-frequency personal radio receivers of the type adapted to be carried on the personof the listener. Receivers of this general type are in increasing demand for a variety of uses. As one example, such receivers are useful in connection with telephone-answering services. In such systems the telephone of a subscriber is connected to a central station whenever the subscriber is away from'his telephone. The person telephoning then can leave a message for the subscriber with the operator `at .the central station. In earlier systems, the subscriber from time to time telephcned the central station to ascertain whether any messages for him had been .re-- ceived. In the telephone-answering system made practical by the present invention, each subscriber is assigned a code number and provided with a personal battery-operated radio receiver so small that it can be carried conveniently in a vest or coat pocket. Whenever a telephone message is received for a subscriber, his code number is recorded on a suitable medium, for example. a magnetic tape, which is reproduced repeatedly, in a cycle along with the code numbers of other subscribers also being paged, and sent out over the air through a high-frequency radio transmitter. Whenever a subscriber wishes to determine whether a message has been received for him at the central station, he switches on his portable receiver and listens through one cycle of the code numbers being broadcast. If he hears his code'number he knows there isa message for him which he can receive by going to the nearest telephone and calling the operator at the central station.

This telephone-answering radio-paging system has been described in order to illustrate the features and advantages of the present invention and not to imply any limitation of use. Radio receiversincorporating the present invention obviously have other utility, but are particularly advantageous for applications wherein the requirements are similar to those of the system outlined above.

The radio receiver described herein as illustrative of the present invention is small, light in weight, and simple in construction. Because of the simple circuit employed and the mechanical arrangement of the parts, highly stable operation is obtained, and the unique construction also makes possible high sensitivity with minimum drain on the batteries that provide the operating power.

lwhen not in use.

reissue sneciiication; matter printed in italics indicates the additions made b y reissue.

One important problem in such receivers is the provision oi a suitable receiving antenna. For example, if the receiver is designed to operate while it is in the pocket of the listener, the

body of the listener tends to shield and t0 detuneI the receiver and anantenna must be provided which extends away from the listener and which is connected to the receiver by a suitable flex Obviously such an extensive an- Moreover, if

ible lead wire. tenna arrangement is undesirable.

the receiver is to be operated while beingcarried 'Ihe present receiver is aaunitary 'device having a built-in antenna and earphone. It is adapted to be hand-held adjacent the ear -of the user when in use, and to be carried in the pocket A relatively short exible wire antenna projects from the receiver and cooperates with other components within a nonshielded portion of the receiver case to provide a. compact and ellicient antenna system. The receiver components are uniquely arranged so that the lower portion of the receiver can be hand-held adjacent the listeners ear without the electrical capacitance of his hand or head [the hand] interfering with the operation or tuning oi the receiver, even though its tuned circuits are unshielded and are positioned in such manner as to form an effective part ofthe an- .tenna' system. These advantageous effectsas well asan economy of parts, is achieved by utilizing certain of the receivercomponents not only to perform their usual functions but, in addition, to serve as an electrostatic shield.

Particular features of construction of the receiver are directed to minimizing the number oi' tubes and the power drain on the self-contained batteries. For example, the receiver requires only two single-function miniature tubes, a feature made possible by the efficient coupling and audio output circuits. 'I'he low power dissipation of the circuit is emphasized by the fact that the entire receiver requires only a single resistor element.

The complete receiver is housed in a relatively long thin case preferably of such shape that it vportion of the receiver is well isolated from the capacity effects of the hand and head of the 'listener without the necessity for-added shielding elements. Without this novel and advan- 1 tageous arrangement, it would be necessary to Figure 2 is an enlarged elevational view of the interior of the radio receiver shown in Figure 1, the connecting leads having been omit-ted to show more clearly the arrangement of the major circuit components;

Figure- 3 is a sectional view of the interior of the receiver taken along line 3-3 oi Figure 2; and

Figure 4 is a schematic diagram'of the electrical circuits of the receiver. As shown in Figure 1, the receiver is housed in a case 2, for example of polystyrene, from which projects a relatively short self-supporting antenna 4. This antenna may be rigid or flexible and may be arranged so as to be out of the way when the receiver is not in use, for example, by sliding the antenna Wire longitudinally down within the case or by exing the wire antenna down along the side of the receiver case 2 and attaching it thereto.

As shown in Figure 4, the electrical circuits may be considered as divided into three portions: an R.F. section, generally indicated at 6; an audio amplier and output portion, genof which is connected, under operating conditions, to the negative terminal of the lament supply battery'34. The end o1' primary winding 54 of the transformer 56 adjacent the radiofrequency choke coil 52 is by-passed to the common negative circuit of the receiver by a small condenser 64. The condenser 64 in combination with the choke coil 52 prevents the radio frequency energy in the antenna circuits from being coupled into the audio frequency circuits.

One end of the secondary winding 66 of the audio transformer 56 is connected to the common negative lead 32, and the opposite end is connected by a lead 68 to the control grid l2 of a miniature audio-amplifier vacuum tube 14, which may be of any suitable type.

The filament 'I6 of this amplifier tube is connected lto the lament supply leads 28 and 32,

erally indicated at 8; and a power supply portion, generally indicated at I0.

The antenna 4 is connected through an an- -tenna coil I2 to a self-quenched super-regenerative detector circuit. In this circuit the lower end of antenna winding I2 is connected by a lead I4 through a condenser I6 and a grid leak resistor [condenser] I8, in parallel with the condenser I6, to the control grid 22 of a miniature vacuum tube 24, which may be of anv suitable type and in this example is a pentode connected to operate as a triode.

The filament 26 of this tube is connected by leads 28 and 32 to a lament supply battery 34, an oiT-on switch, generally indicated at 36, being connected in series with the negative supply lead 32.

The anode 38 of the tube 24 is connected by a lead 42 'to one end of a parallel resonant circuit comprising a coil 44 connected in parallel with tuning condenser 46 'ind a fixed condenser 48. The opposite end of this tank circuit is connected tn the lead I4 in the control grid circuit of tube 24.

The quench frequency of the super-regenerative detector will depend upon the characteristics of the anode-grid feed-back circuit and in particular upon the time constant of the gridleak resistor I8 and the condenser I 6.

The audio frequency signal is coupled from the lead I4 in the grid circuit of the detector tube 24 through a radio-frequency choke coil 52 to one end of the primary winding 54 of a miniature inter-stage audio transformer 56. The opposite end of this winding 54 is connected by a lead 5,8 to the positive terminal of a plate supply battery 62. the negative terminal in parallel with the lament 26 of the detector tube 24. The anode 'I8 of this tube is connected through a miniature audio-frequency choke coil or inductance 82 to the positive supply lead 58, which is connected also to the screen grid B4 of the audio output tube 14. A crystal-type earphone, diagrammatically indicated at 86, is connected in shunt with the choke coil 82 and is positioned in the front wall of the receiver case 2, as shown in Figure 3, so that it may be placed adjacent the ear of the listener.

The physical relationship of the components described above in connection with the circuit diagram of Figure 4 will be apparent from Figures 2 and 3. As shown in the latter ngures, the coils I2 and 44 are supported on suitable low-loss forms 88 and 92, respectively, which for example may be of polystyrene molded in tubular form. The detector tube 24 is mounted, as shown, between these two coils near the back of the case 2. The adjustable tuning condenser 46 is mounted near the lfront of the case 2, directly opposite the tube 24, and the tlxed condenser 48 is mounted directly beneath the variable condenser 46. The condenser 46 rnay be .so positioned that the frequency of the tuned circuit can be adjusted by means of a tuning screw driver through a suitable opening in the case 2. However, because of the stability produced by the circuitry and arrangement of parts, it is not necessary to provide any means for adjustment of the receiver by the user for fixed-frequency applications. The antenna 4 and the antenna coil I2--are tuned to the desired xed frequency by cutting the antenna to the length that produced optimum response v characteristics.

Immediately beneath the coils I2 and 44 is a terminal strip 94 by which connections are made between the radio frequency section 6 and the audio amplifier section 8 and power supply section III. The radio frequency choke coil 52 is positioned adjacent the terminal strip 84, as shown in Figures 2 and 3. The inter-stage transformer 56 and the output inductance 82 are mounted immediately beneath the terminal strip 94. The audio amplifier tube 14, is mounted, in inverted position, adjacent the inductance 82.

The plate supply battery 62 is mounted, as shown, near the lower end of the case 2 and its terminals at either end are protected by insulating strips 96 and 88. The i'llament supply battery 34 is mounted adjacent the plate supply battery 62. The switch 36 is mounted near the bottom of the case 2 and operated by a button |02. which project through a slot in the bottom of -thisis necessary, and moves the control button |02 of the switch It into the "on" position. The user then graps the lower end of the case I in his hand as shown in Figure l, and places the earphone 8l adjacenthis ear with the upper partof the receiver case 2 and the antenna 4 extendr ing rearwardly and upwardly head of the listener. r

In actual practice, this receiver has been found away from the to provide-excellent sensitivity and to be sumciently stable and selective'as to b e entirely satisfactory for its intended use. The drain von the -supplybatteries is very low so that, with intermittent operation such as wouldbe occasioned by use in a telephone-answering system, they are certain to have anadequate life. For example,

with a receiver utilizing thev components hereinafter described operating in such service, battery life of several months has been obtained.

.With fixed tuning, as is provided in the present receiver, it is of course essential that the A electrical capacity of the hand and head of the user not affect the frequency of operation of the receiver. As explained above, this novel receiver is so arranged that the radio-frequency section i of the receiver is unshieldedso that the coils l2' and 44 operate inV conjunction with the wire antenna 4 to form a highly sensitive antenna system.

A These features are facilitated by the particular arrangement of the parts as described above; For example, the'metal parts of the terminal strip 94, the transformer 56, the inductance 82, and the tube 14, all of which parts are at substantially the same radio frequency potential, serve as an eifective barrier or shield between that portion of the case 2 which is held in the hand of the user and the radio-frequency section B that controls the frequency of operation of the receiver and determines its sensitivity. Thus, highly stable operation of a hand-held receiver is obtained while'at the same tima attaining the maximum sensitivity.

` The radio frequency section 5 although basically a conventional super-regenerative receiver in which the quench frequency is determined by the time constants of the feed-back circuit between the anode 38 and the control grid 22 of tube 24, is one of utmost sensitivity and stability.

The particular circuit connections and components of the audio section 0V are such as to provide maximum output with a minimum of tubes. Thus. additional gain is provided by the use of the step-up inter-stage transformer 5l, and by the output circuit connected to the anode 1I of amplifier tube 14. In this output circuit, the earphone 88. as mentioned above, is preferably a crystal-type, that is, it is a high impedance voltage-operated device having a capacitive reactance. This earphone is connected in shunt with the output choke 82 so that the capacitance of the earphone 88 in conjunction with the-induc-l tance 82 forms a parallelcircuit that is resonant within the audio frequency range. Thus substantial voltage is built up across the terminals of the earphone 8l which effectively increases the..

gain of the receiver, resulting in a material saving in the electronic tube amplincation required in the receiver.

The capacitance and the inductance of all parts of the receiver at the upper end thereof, including the antenna 4, antenna coil I2, coil 44, other parts of the radio frequency section or detector circuit, and even the mountings of the parts and the casing material, are fired at values at which the radio frequency section is in resonance to signais of the predeterminedfired frequency on which the receiver is to operate. Also, the receiver thus made to operate on a fixed frequency is so dimensionedvand shaped that when it is held against the ear of the operator as described, the

upper end of the receiver which contains the radio frequency section is positioned supciently away from the operator's head so that his body capacitance does not put the circuit out o! resonance to said fixed frequency. i. e., does not detune the receiver. r

In one particulaembodiment of the invention which has operated in a. complete. satisfactory manner in a radio-paging system such as that described above. the case 2, which houses the entire receiver was 5.75 inches in length, 1.75 inches in width. and 0.70 inch in depth. The total weight of the receiver was six ounces. The antenna 4 was a flexible wire between three and four inches in length, and the antenna coil i2 and the anode-grid coil 44 were each wound ony a polystyrene rod 1.75 inches in length and 0.375 inch vin diameter. Eighteen turns of No. 16 solid .copper Wire were used to form each coil, adjacent turns of each coil being spaced a micromicrofarad fixed ceramic capacitor 48 to provide a somewhat smoother tuning characteristie. The condenser Ii in the grid circuit of the tube 24 has a capacity of twenty microxnicrofarads and was shunted by a twenty-two megohm' gridleakresistor IB. The radio frequency choke. coil 52' was wound on a plastic composition form 0.70 inch in length and 0.25 inch in diameter and had forty-two turns of No. 28 solid copper enameled wire. The condenser 64 was a tubular ceramic type and had a capacity of five thousand micromicrofarads. The inter-stage coupling transformer -56 had a step-up ratio of three tonne, and the ioutput choke B2 hadan inductance of about forty millihenrys. The super-regenerative detector` tube 24 was a type vCK522AX pentode tube. connected as a triode and operating at approximately forty-three megacycles and the quench signal had a repetition frequency of approximately ten kilocycles'. The audio .output tube 'I4 was a pentode of the type CK533AX. The filaments were supplied :by the battery 34, which was an ordinary one and one-half volt smallsizeA flashlight cell, and the plate voltage was supplied by the hearing-aid-type battery 62 which delivered thirty volts. Y

It will thus be seen that the radio receiver embodying my invention is well adapted to attain the ends and objects hereinbefore set forth and to be veconomically manufactured since the separate'parts are well suited-to standard production methods.' It is `to be understood', of course, that various modifications may be made in the emb odlment of my invention in'order to best adapt the'invention' for a particular"use. It is to be understood, however, that such'modications may wellbe'withn the scope and spirit of the present 4said short antenna, an audio frequency amplifier 7 invention as denned and set forth in the following claims.

I claim:

l. A radio receiver of a size' to be grasped in the hand to be held against the ear of the operator for receiving radio frequency transmission, comprising an'elongated casing, a detector circuit including an antenna coil disposed in the upper end said detector circuit, a power supply for said detector and said amplifier, said casing including a hand-gripping portion located at the lower end o! said casing remote from said detector circuit to prevent shielding of said detector by the hand, and a speaker located in said hand-gripping por: tion and connected to said amplifier.

2. A radio receiver according to claim l in which said hand-gripping portion of said casing includes a surface portion protruding out of the plane o1 one side of said casing, and in which said speaker is located in said protruding portion whereby, as the speaker is held against the ear of the operator, the protruding portion will space the main part of the casing including the detector away from the head of the operator, thus reducing shielding.

3. A receiver according to claim l, and a ilexible self-supporting antennaconnected to said antenna coil and extending out from the top of said casing.

4. A radio receiver to be held against the ear of the operator for receiving radio frequency transmission, comprising a detector, an audio amplifier electrically coupled to said detector, a speaker connected to said amplifier, and a source of power for said circuit elements including at least one dry cell battery, a thin elongated plastic casing containing the components of said circuit, the thickness of said casing being just sutlicient to contain said dry cell battery, said detector being located in the upper end of said casing. and a hand-gripping portion at the lower end thereof and remote from said detector to prevent shielding of the detector by the hand, said speaker being located in the hand-gripping portion of said Y casing, and a flexible antenna connected to said detector and extending from the top of said casing.

5. A radio receiver of a size to be grasped in the hand and held against the ear of the operator for receiving radio signals on a predetermined fired frequency, comprising, an elongated casing, a short antenna extending from the upper end of said casing, an antenna coil disposed in the upper end of said casing, a detector circuit disposed in the upper end of said casing, said antenna being connected to said circuit through said antenna coil, at least a portion of said casing in the vicinity of said antenna coil being pervious to radio waves to provide pickup strength-with disposed in said casing and electrically coupled to said detector circuit, a power supply for said detector circuit and said amplifier, said casing including a hand-gripping portion located at the lower end of said casing remote from' said detector circuit, a speaker located in said handgripping portion and connected to said amplifier, the capacitance and inductance of all parts of said receiver at the upper end thereof, including the upper end of the casing itself, being fired at values at which the circuit is in resonance to signals of said predetermined fixed frequency.

6. A radio receiver according to claim 5 in which said hand-gripping portion of said casing includes a surface portion protruding out of the plane of one side of said casing and in which protruding pontion said speaker is located, whereby as the speaker is held against the ear'of the operator, the protruding portion will space the upper end of the casing away from the head of the operator so that the capacitance of the head of the operator does not render said circuit nonresonant to said fzed frequency.

7. A radio receiver of a size to be grasped in the hand and held against the ear of the operator for receiving radio signals on a predetermined fired frequency, comprising, an elongated casing, a short antenna extending from the upper end of said casing, an antenna coil disposed in the upper end of said casing, a super-regenerative detector circuit disposed in the upper end of said casing, said antenna being connected to said circuit through said antenna coil, the upper end of said casing adfacent to said antenna coil and said detector circuit being pervious to radio waves for maximum pickup strength with a short antenna, an audio frequency amplifier circuit disposed in said'casing vand'including a transformer, an audio inductance and an audio output tube, aterminal strip disposed in said casing between said circuits, said audio circuit being electrically coupled to said detector circuit through said terminal strip, a power supply for said detector and said amplifier circuits, said casing including a hand-gripping portion located at the lower end of said casing remote from said detector circuit, and a speaker located in said hand-gripping portion and ,connected to said amplifier circuit, said terminal strip, transformer, audio inductance and audio output tube being located in the upper part of the said hand-gripping portion immediately below said detectorcircuit so as to assist in shielding the detector circuit from the capacitance of the hand and head of the operator when the receiver is held against the ear during use.

8. A radio receiver of a size to be grasped in the hand to be held against the ear of the operator for receiving radio frequency transmission, comprising an elongated casing, a detector circuit including an antenna coil disposed in the upper end of said casing, at least a'portion of said cxzsing in the vicinity of said antenna coil being pervous to radio waves, an audio frequency amplifier disposed in said casing and electrically coupled to said detector circuit, a power supply for said detector and said amplifier, said casing including a hand-gripping portion located at the lower end of said casing remote from said detector circuit, and a speaker located in said handgrzppzng portion and connected to said amplifier.

RICHARD R. FLORAC.

References Cited in the file of this patent or the original patent

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