US2342167A - Multiple radio recorder - Google Patents

Description

Feb. 22, 1944. J. T. POTTER MULTIPLE RADIO RECORDER Filed Feb. 23, 1939 3 Sheets-Sheet 1 INVENTOR J/ua ZZPoZ-Z'er WWW ATrOR NEY Feb. 22, 1944. J. T. POTTER 2,342,167

MULTIPLE RADIO RECORDER Filed Feb. 23, 1939 3 Sheets-Sheeb 3 759- I5! 1 g I55 ig I24 122125' '34 INVENTCR John If Pofiier saw/WM ATTORNEY Patented Feb. 22, 1944 UNITED STATES PATENT OFFICE MULTIPLE RADIO RECORDER John '1. Potter, Brooklyn, N. Y.

Application February 23, 1939, Serial No. 257,984

4 Claims.

The present invention relates to recorders and in particular to methods of and means for recording the operation of a plurality of radio receivers.

One object of the present invention is to record at a central point and on a single re ord sheet the tuning and operating conditions of a plurality of radio receivers located at remote points.

Another object is to provide such recording in accordance with spaced impulses of audio or super-audible alternating current voltage wherein the time relations of the impulses indicates the information to be recorded.

A further object is to provide greater sensitivity and selectivity against noise and hence to make greater recording distances possible than hitherto available.

Still another object is to provide an impulse generator to be connected to the radio receiver which sends out an impulse of considerable power over a short interval while requiring only a small input power at any given instant.

Another object is to generate at the radio receiver an impulse of short duration and of a frequency which varies thru a narrow range in or der to make useful a high degree of frequency selectivity at the central station and yet permit some drift in average frequency of the generated impulses.

In the copending application entitled Multiple recorder, now Patent Number 2,249,324, issued July 15, 1941, is shown and described a recorder adapted to record the tuning and operation of a plurality of radio receivers on a single record sheet. At each radio receiver a commutator turns on a fixed frequency oscillatorfor a short interval which is spaced within a second and longer interval in accordance with the tuning'conditions of the receiver. The longer intervals are equal for the various receivers and are phased so that they are consecutive but do not overlap. The longer intervals for all the receivers may add up to a convenient recording time cycle as for instance one minute. At the recorder signals generated by the various radio receiver recorder oscillators are amplified by a fixed frequency amplifier and recorded on a record sheet which is conveniently in the form of a cylinder which makes one revolution per recording cycle. Thus the operation of a particular receiver is recorded in a unique column axially of the cylinder and the reception of a particular station by the receiver is recorded in a line within the column.

'I'hegeneral' system employed in the present invention is the same as given above but certain novel improvements have been made. In order to increase the sensitivity of the recorder amplifier in order to permit greater recording distances and also in order to increase the selectivity of the amplifier against noise and other interferences the amplifying is done in two distinct stages at different frequencies. The received signals are first amplified with as much gain and selectivity as is economical and practical and then the signals are heterodyned to a low frequency and again amplified with a large amount of gain and selectivity. The second frequency is chosen as low as possibl consistent with the presence of normal amounts of harmonies of the local alternating current power lines and other line noises.

At the radio receivers a substantial improve.- ment has been produced by storing energy during periods between impulses and releasing it in accordance with the information to be recorded. In addition, the frequency of the impulse is varied slightly during generation in order that the high degree of selectivity of the recorder amplifier may be useful in the presence of nominal amounts of drift in average frequency due to temperature and other frequency changing effects.

In the drawings:

Fig. 1 shows a schematic diagram of a recorder embodying the present invention.

Fig. 2 shows a radio receiver impulse generator unit embodying my present invention.

Fig. 3 shows a detail of the recorder.

Fig. 4 shows an additional recorder detail.

Fig. 5 shows a circuit detail.

Fig. 6 shows a method of phasing the receiver units.

Fig. '7 shows an auxiliary impulse generator useful in phasing operations.

Fig. 1 shows a complete central station amplifler and recorder. While other methods of transmission may be used the description will be particularly in connection with transmission of recording signal impulses over alternating current power lines common to the radio receivers and central recording unit. Lines and 2 are connected to the local power lines. Fuses 3 and 4 are provided to protect the apparatus in case of short circuits within it. Wires 5 and 6 go to primary I of a conventional power supply transformer for supplying heater current to the various amplifier tubes and direct current for the plates and grids of the tubes and for the recording magnet 99. Branch wires 8 and 9 connect transformer primary I2 to the power line thru blocking condensers I9 and H. Secondary I3 is coupled to primary i2 and is tuned to the operating frequency of the radio receiver impulse generating units shown in Fig. 2, which may conveniently be of the order of 100 kilocycles. The selected voltages appearing across secondary I3 are applied to grid I9 of pentode amplifier tube I5. The output of tube I5 appearing at its plate 22 is further selected by tuned load circuits I7 I9 and the coupled tuned circuit l9-29 all tuned to the same generated frequency. The voltage across coil I9 is applied to the second amplifier tube 2I at its grid 23. Output voltages on plate 24 are again selected by tuned circuits 2526 and 2'I--28 and applied to grid 33 of the multigrid converter tube 35. Cathode 29, control grid 39 and anode grid 3| of tube 35 function With transformer 3'I38 tuned by condenser 49 to produce heterodyning oscillations at a desired difierence frequency with said generated frequency as for instance 95 kilocycles. The 5 kilocycle diiference frequency appears at plate 34 and across plate load resistor 49. Since the 95 and 100 kilocycle voltages-"are no longer desired they are eliminated by means of the filter composed of choke 45 and'condenser 41. The 5-kilocycle voltage to be further amplified and utilized to operate the recorder is'applied to grid 49 of amplifier tube 59 by means of a tap on volume control 93 thru blocking condenser 49. The amplified 5 kilocycle signal on plate 5i is made large by loading plate 5I with inductance 53 tuned to 5 kilocycles by means of condenser'52. The signal voltage across inductance 53 is applied to grid 99 of am-' plifi'er tube 57 thru blocking condenser 59 and across grid resistor 55-. Amplifier tube 51 is a triode particularly suited to-operate a diode rectifier. The amplified signal on plate 59 loaded by resistor 99 is applied to a diode rectifier con-v sisting of plates 59 and cathode 99 of diode-triplate 98 is passed thru magnet 659 of the recorder unit and thus operates pen 92. The recorder consists in cylindrical drum covered by a record sheet I9 mounted on a shaft I5 and driven by synchronous motor 11. Motor ll is operated from the same alternating current source as the radio receiver signal generating units in order to provide synchronous operation. Magnet 69 is moved along the recorder'drumby the lead screw 8| driven from sprocket 89-by chain 78 and a sec ond sprocket I9 on motor'shaft I5. Motor ll includes suitable reducing gears to produce a speed of shaft I5 of the order of one revolution per minute. Sprockets 'I9and 99 are proportioned so that with a properly chosen pitch in lead screw BI magnet 99 is caused to traverse the drum in a suitable time as for instance 24 hours. In order to produce an equal marking intensity regardless of the strength of received signals pen 82 is operated by gravity. Plate current in tube 61 is adjusted by proper choice of bias battery 94 voltage so that magnet 69 is energized and pen 92 is kept ofi of the record sheet inthe absence of received signals. Received signals are rectified and applied to grid 95 as negative impulses causing magnet 69 to release allowing pen 82 to contact record sheet I6. Control 48 is used to set therecording level abovethe noise level.

In Fig. 2 is shown a circuit diagram of an impulse generating unit suitable for attachment to a radio receiver for generating impulses indicating the operation and tuning conditions of the receiver to be recorded at the above described central or recording station. The impulse generator comprises a thermionic vacuum tube oscillator and a motor driven contactor sweeping over a commutator connected to a multi-point switch associated with the radio receiver tuning mechanism. The oscillator circuit utilizes a vacuum tube 99 having a cathode 99, control grid and plate 97. This tube is connected to an oscillatory circuit made up of grid coil 99 tuned by condenser 92, plate coil 89 coupled to grid coil 99 and tuned by condenser SH, and grid resistor 93 Joy-passed by grid condenser 94. This constitutes a feedback oscillator with grid and plate tuning. Oscillator voltage impulses are fed to the local power line by means of coil 88 coupled to plate coil 89, blocking condensers 8'I-89 and line plug 83.

Cathode 93 is energized from the filament transformer secondary 99 the primary I99 of which is also supplied from the power line thru leads I9I, I92 and I99 and relay contact I98, so that tube 99 is operable only when relay I9II98 is closed. Plate voltage for tube 96 is supplied from condenser II2 which is charged thru resistor II9 from the high voltage direct current source I93 of the radio receiver I44 being monitored thru lead I94. Oscillator tube 99 is rendered inoperative further by plate current cut-off bias applied to heater source '99 from resistor I I I and through resistor H3. Resistors III and H3 are proportioned to keep plate current to tube 96 substantially cut-oil or at least small enough so that the tube 99 does not oscillate. Resistor H3 is shorted at intervals in a manner to be described thus removing the cut-off bias from tube 96 and causing it to oscillate strongly dissipating the charge in condenser I I2. denser II2 recharges thru resistor H9 to essentially the voltage of source I93. Since the periods of oscillation are very short compared to the periods between oscillation the average charging current. drawn from source I93 may be made small compared to the current drawn for the short oscillation intervals from condenser I I2. As an example the intervals between impulses may be 109 times the periods of the impulses and tube 99 may draw 1G0 milliamperes during the oscillation periods while drawing only 1 milliampere from source I93. This provides efficient operation and permits operation of a powerful oscillator from a small capacity power supply without disturbing the normal operation of the power.

supp y.

Radio receiver I44 is to be monitored. It is connected to antenna A and ground G or other suitable energy collecting means. While other types of tuning mechanism may be monitored, for purposes of explanation a variable tuning j condenser I29 is shown in receiver I44. 0n the electrical connection between contactor MI and.

common output lead I28. The switch also-in cludes end supports I38 and I39 and anchor wire. or string I99 forrestraining longitudinal motion of the switch. Wire or string I49 may be fe s tene d Between intervals c0n-.

to a suitable and convenient point of the chassis or cabinet of I44 so that the switch body is held in a line substantially tangent with pulley I3I. Contacts I32, I33, I34, I35 and I36 are adjusted on a particular receiver so that as condenser I29 is tuned contactor I4I makes contact with them at condenser settings corresponding to radio stations which are to be recorded.

Timed impulses are generated by means of a motor driven commutator operated in connection with the switch and oscillator described above. The commutator comprises commutator points I22, I23, I24, I25 and I26 connected to switch points I32, I33, I34, I35 and I36 respectively; motor driven commutator arm I2I; and synchronous motor II6 connected to the power line by meansof leads H4 and H and line plug 83. Arm I2I is driven at a convenient speed as for instance one revolution per minute thru reduction gear box 1. Gear box II! is mounted on a plate H8 having a semi-circular slot H9 and the said plate is clamped to motor II6 by means of screw I20. The phase relation of arm I2I with respect to the alternating current power line voltage may be adjusted by releasing screw I20, turning plate II8 to a desired position and replacing screw I20. Commutator segments I22 to I26 inclusive are equally spaced and occupy a predetermined angle as for instance six d grees. As arm I2I rotates it completes a circuit thru the receiver condenser operated switch and leads i2! and I28 corresponding to the position of contactor MI and hence condenser I29 and the time and phase relation of arm I2I shorting cut-on bias producing resistor I I3 and causing tube 96 to oscillate feeding an impulse of oscillator voltage to the power line. The additional commutator point I45 is connected to the common switch lead I28 so that at each rotation of the commutator arm I2I a signal is generated indicating that the radio receiver is turned on Whether or not one of the preselected stations is tuned in.

The operation of a system including a number of receivers will now be described. A particular receiver I44 is turned on by a listener. When the receiver has warmed up voltage appears in source I63 energizing relay coil I01 closing contact I08 and thus energizing filament or heater 98 of tube 96. At the same time condenser II2 starts to charge thru resistor IIO until it reaches the voltage of source I03. Motor II 6 is operated continuously and every minute sweeps contacts I22 to I26 inclusive with arm I2I. If receiver I44 is tuned to a station the reception of which is to be recorded one of these commutator points I22 to I26 is energized thru contact MI and one of the contacts I32 to I36 inclusive. When arm I2I contacts an energized segment, resistor H3 is shorted and an impulse of oscillator voltage is applied to the power line. This impulse-is received at the central station and recorded on the record sheet by the central station amplifier and recorder described above. While tube 96 is oscillating, it is drawing a heavy current from condenser II2 causing the voltage across it to fall. This falling voltage causes the oscillator frequency to vary slightly. For instance, a central station may be tuned accurately to 100 kilocycles while the oscillator may oscillate from 99 to 101 kilocycles. It will be seen that the mean frequency may vary plus or minus 1 kilocycle and it will still pass thru 100 kilocycles while it is being impulsed. This frequency variation permits a high degree of selectivity to be used in impulse is picked up and the central unit and a variation of the oscillator mean frequency and still proper recording of the signal will be accomplished.

With the commutator segments occupying six degrees, for instance, sixty receiver units may be operated into a single recorder without overlap by phasing the receiver impulse generating units to be complementary in time spacing. This spacing and mode of operation is more particularly described in the co-pending application cited above.

In a radio receiver recording system, such as the one herein described, it is important that further recording be prevented in case of momentary power failure since in general such failure will destroy the proper phase relations between the receiver units and the central station recorder. Fig. 5 shows a relay I45i46I4'I- I 48I50 which is interposed between the power source wires 8485 and the leads IOII02 and II4-II5 going to the oscillator tube filament transformer 93I60 and the commutator motor II6 respectively. This relay is designed to close contact I48 energizing the oscillator and motor as long as the power is uninterrupted but opens and stays open until reset in case of temporary power failure. From power supplied through the current limiting resistor I43 relay coil I46 energizes core I45, attracting armature I41 against spring I50, thus closing contact I48.

Fig. 6 shows a method of phasing the various receiver units. An impulse is transmitted once for each revolution of the commutator arms I2I, I2I, IZI etc. by apparatus as in Fig. 7. This the operator listens to it in a pair of earphones. Each receiver unit is provided with an auxiliary arm I56, I 56, I56" etc., each phased by a different angle with the main commutator arms IZI, I2I, I2I" etc. The difierence angles a, b, 0, etc., differ by the angle a subtended by the commutator contacts I22, I23, I24, etc. The auxiliary commutator arm is adapted to short a pair of contacts I54I55 in each unit completing a circuit thru leads I58 I59 and line plug I6I to a neon lamp I60. Each receiver unit is phased until the neon lamp I60 flashes in synchronism with the impulses received in the earphones. When all the units are so phased, they will operate at the relative phase angles determined by the auxiliary arms I56, I56, I56", etc., which have been predetermined to be the desired phasing angles.

Fig. 7 shows an impulse generator I66 having a single synchronously driven commutator arm I64 driven at the same rate as arms I2I, I2I', I2I etc. Arm I64 shorts contacts I62I63 and by turning on an oscillator or other suitable means, sends the phasing pulse over the power line by means of wires I 6'II 68 and line plug I66. This phasing pulse is generated while the various receiver units are being set up and phased or in case of power failure for rephasing purposes and is turned off while recordings are being made.

While one embodiment of this invention has been shown and described, it is intended to limit it only in accordance with the spirit and scope of the invention as set forth in the appended claims.

I claim:

1. In a radio receiver tuning condition and operation determining system, the combination of, a selector switch adapted for selective operation in response to the tuning condition of the radio receiver, a normally inoperative oscillator, a motor driven commutator for rendering said 'oscillator operable 'in'accordance with the position of said selector switch, and a condenser and resistor connected to said radio receiver and receiving current therefrom for storing energy at a substantially constant rate to provide power for energizing said oscillator during its periods of operation.

2. In a radio receiver tuning condition and operation determining system, the combination of, a selector switch adapted for operation in response to the operation and tuning of the radio receiver, a normally inoperative oscillator, a motor driven commutator for rendering said oscillator operable in accordance with the position of said selector switch, a condenser for continuously storing energy for energizing said oscillator during its periods of operation, a source of direct current within said radio receiver, and a resistor connected between said source and said condenser for limiting the current supplied to said condenser.

f 3. In a radio receiver tuning condition and operation .determining system, the combination of, amulti-point switch adapted for operation in response to predetermined tuning conditions of said radio receiver, a normally inoperative oscillator, means for rendering said oscillator operable at predetermined time intervals in accordance with the position of said multi-point switch, means for deriving electrical energy from the radio receiver, means for storing said energy for energizing said oscillator during the time. of inoperativeness of said oscillator, and means for releasing said stored energy during intervals of operativeness of said oscillator.

4. The system as claimed in claim 1, and means for rapidly varying the frequency of said oscillator through a selected frequency.

JOHN T. POTTER.

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