US2166674A - Indicating device - Google Patents

Indicating device Download PDF

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Publication number
US2166674A
US2166674A US646074A US64607432A US2166674A US 2166674 A US2166674 A US 2166674A US 646074 A US646074 A US 646074A US 64607432 A US64607432 A US 64607432A US 2166674 A US2166674 A US 2166674A
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United States
Prior art keywords
tuning
potential
resistor
signal
transformer
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Expired - Lifetime
Application number
US646074A
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English (en)
Inventor
Loy E Barton
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RCA Corp
Original Assignee
RCA Corp
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Filing date
Publication date
Priority to NL39161D priority Critical patent/NL39161C/xx
Application filed by RCA Corp filed Critical RCA Corp
Priority to US646074A priority patent/US2166674A/en
Priority to DER89370D priority patent/DE704870C/de
Application granted granted Critical
Publication of US2166674A publication Critical patent/US2166674A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03J—TUNING RESONANT CIRCUITS; SELECTING RESONANT CIRCUITS
    • H03J1/00—Details of adjusting, driving, indicating, or mechanical control arrangements for resonant circuits in general
    • H03J1/02—Indicating arrangements
    • H03J1/04—Indicating arrangements with optical indicating means
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03J—TUNING RESONANT CIRCUITS; SELECTING RESONANT CIRCUITS
    • H03J3/00—Continuous tuning
    • H03J3/02—Details
    • H03J3/12—Electrically-operated arrangements for indicating correct tuning
    • H03J3/14—Visual indication, e.g. magic eye

Definitions

  • My invention relates to indicating devices and, more particularly, to tuning indicators, dials, etc., adapted for use in radio receivers.
  • Tuning meters are relatively expensive. Also, they are of necessity fragile and do not stand up Well in service or during shipment of a receiver from the factory to its ultimate destination.
  • an object of my invention to provide an inexpensive tuning indicator particularly adapted for use in receivers of the automatic gain-control type.
  • Another object of my invention is to provide a combined tuning indication and dial-lighting system.
  • Another object of my invention is to provide a system of the type referred to that shall also be capable of giving an indication of the adjustment of a background noise control device.
  • the power-transformer which supplies energizing potentials to the various thermionic devices, the loudspeaker, etc.
  • the secondary of the transformer is connected to the plate and cathode of a control tube, the impedance of which is proportional to the potential applied to the grid thereof.
  • the grid potential is obtained from a point in the receiver circuit, the potential of which varies according to the amplitude, or inversely as the amplitude in some instances, of an incoming signal. Accordingly, the impedance of the control tube and its elfectiveness as a load on the step-up transformer is a function of the signal amplitude, and the pilot lamp uctuates in brilliancy as the impedance changes.
  • I also so connect another pilot lamp of somewhat higher voltage across the primary of the step-up transformer that its intensity decreases as the intensity of the series lamp increases, and vice versa.
  • a lamp of the same voltage as the seriesconnected lamp may, of course, be used but, in
  • the several lamps may be differently colored, they may both be utilized for dial-illumination, or they may be disposed in any suitable position on the radio-receiver cabinet Where they are visible to the operator.
  • Translucent color filters may be utilized instead of colored lights, as well as various combinations of screens, mirrors, or lenses, without departing from the spirit of the invention.
  • Fig. 2 is a fragmentary diagrammatic View of an alternative embodiment of my invention
  • Fig. 3 is a front elevational view of a tuning dial showing the appearance thereof when the receiver is in the tuned in condition
  • Fig. 4 is a fragmentary sectional View of the receiver dial, taken along a line corresponding to the line 4-4 in Fig. 3.
  • the primary object of my invention is to provide a tuning indicator which will enable a receiving system of the automatic gain control type to be accurately brought into syntony with a desired incoming signal without reliance necessarily being placed upon the volume of sound output therefrom.
  • radio receivers of the automatic gain control type utilize a direct current, proportional to the amplitude of an incoming carrier wave, for the purpose of controlling the bias applied to the input circuits of one or more amplifying tubes.
  • my invention may be applied to a radio receiver equipped with a volume control system of substantially any wellknown type, I find it quite expedient to combine it with an improved automatic volume control system Which I also have invented.
  • the second detector includes a thermionic cathode 3, two diode electrodes 5 and 1, a control grid 9, and an output anode II.
  • One of the diode electrodes, 5, is connected back to the cathode through the secondary winding of an intermediate frequency transformer I3 and a resistor I5. From a point on the resistor furthest away from the cathode, a connection extends to the control grid, the connection, preferably, including a resistor I9 which impedes the flow of grid intermediate frequency current.
  • the cathode is connected to the negative terminal 2
  • a bleeder resistor 21 and the eld winding 29 of a loudspeaker are connected in shunt to the terminals of the high potential source, and a point 3
  • the resistor 22 in the cathode circuit is of such magnitude that the voltage drop thereacross occasioned by plate current in the detector tube I during the no signal condition is greater than the drop across the loudspeaker field winding 29. The reason for this difference in potentials will be hereinafter apparent.
  • the intermediate frequency is impressed upon the diode plate 5 through the intermediate frequency transformer I3, it is rectified and direct current, varying at audio frequency, due to modulation, flows in the resistor I5 included in the input circuit.
  • the current is in such direction that the control grid 9 is negatively biased with respect to the cathode of the tube and, as a result, the current in the resistor 22 connected to the cathode decreases as a signal is tuned in, and the potential drop thereacross also decreases.
  • the second diode plate 1 is connected over a resistor 35 to ground and the said plate is, therefore, at a negative potential, normally, with respect to the cathode 3.
  • the diode plate and the cathode approach the same potential and, eventually, if the signal-carrier is of sufficient amplitude, the cathode will become negative with respect to the diode plate.
  • current then flows in the resistor 35 connected between the diode plate and ground, which creates a potential drop thereacross.
  • the potential drop developed along the resistor may be utilized to apply bias more negative than normal to an amplifier tube 31, or to a plurality of tubes (not shown) which bias becomes more and more negative as the signal carrier amplitude increases, and vice versa.
  • the primary function of the automatic volume control network is to correlate the gain in the system to the amplitude of an incoming signal, which varies because of fading and because of the distance Vand strength of the transmitting station. If it is assumed, however, that the signal is relatively constant in amplitude, the diminution of current in the resistor 22, as well as the increase in current in the resistor 35, are indicative of the accuracy of tuning of the receiver, exact tuning being accompanied, as is obvious, by respective minima and maxima.
  • I nd it expedient to utilize the change in potential across the said resistor to control the impedance of a thermionic tube which, in turn, serves as a load upon a circuit supplying energy, differentially, to a plurality of light sources.
  • I provide a secondary winding 39 on the main power transformer 4I which supplies energizing potentials to the receiver, and connect the primary winding of a step-up transformer 43 and a plurality of light sources 45 and 41 in series therewith.
  • the primary winding is also tapped at an intermediate point 49, and an additional light source 5I, or light sources, are connected across the tapped portion.
  • the potential developed by the Winding on the power transformer which supplied the light source is 7.5 volts and each of the lamps is rated at 2.5 volts.
  • the secondary winding of the transformer 43 is connected between the anode 53 and cathode 55 of a therminoic tube 51 of the screen grid pentode type,hereinafter called the control tube, having, in addition to the said anode and cathode, a suppressor grid 6 I, a control grid 63, and a screen grid 65.
  • a connection 61 including a current limiting resistor 69 extends from the control grid to the cathode of the second detector I and a con-- nection 1I extends from the cathode of the control tube to groimd.
  • the screen grid may be connected by a conductor 13 to an appropriate point on the bleeder resistor 21, in order that they said grid may be maintained at the proper positive potential.
  • a control tube of the screen grid type is preferable if the changes in potential available from the resistor 22 are of small magnitude. It is not to be inferred, however, that my invention is limited to such tubes, since tubes of many other types may be substituted therefor, and, in the specific circuit illustrated, a three-element control tube may be used, if desired.
  • the cathode of the second detector When no signal is being received, the cathode of the second detector is positive with respect to ground, which results in a slight grid current to the grid of the control tube through the current limiting resistor 69.
  • the resistance of the said resistor is large as compared to the resistance of the resistor 22 in the cathode circuit of the second detector, and also' with respect to the resistance of the grid of the control tube when it is positive. Accordingly, the grid voltage on the control tube is essentially zero when no signal is being received and the plate resistance of the tube is minimum, which resistance is reected to the primary of the transformer.
  • the low resistance reflected to the primary permits the series-connected lamps, and ⁇ 41, to be supplied with energy, and to be lighted to approximately their full brilliancy, whereas the voltage across the tapped portion of the primary is suiiiciently low that the tube 5i is substantially deenergized.
  • thecathode of the second detector tube becomes less and less positive, until it reaches ground potential with practically no chang-e in illumination of the series connected lamps because of the practically constant zero biasing potential still being applied on the control tube.
  • the series-connected lamps will have minimum brilliancy while the shunt-- connected lamp will be giving off its maximum light for the particular signal strength and sensitivity setting of the receiver.
  • the light sources 45 and 41 remain substantially fully brilliant until the cathode of the detector tube, by reason of decreased current in the resistor 22, becomes slightly negative with respect to the diode electrode l.
  • the receiver may be made so insensitive as to fail to supply sufficient signal to the detector tube to operate the automatic volume control and to control the light sources.
  • the signal from the loudspeaker may be of any value from zero to its value at the threshhold of the automatic volume control system or to the point at which the automatic volume control is delayed.
  • the fading of the signal cannot be compensated, nor will the volume from the loudspeaker be constant.
  • the tuning lights will not respond, which fact indicates to the operator that the adjustment of the noise suppressor is such that a constant volume of audio signal cannot be received. If the noise control is then adjusted so that the automatic volume control can function, the tuning lights respond, which indicates that the noise suppressor adjustment is such that the signal is substantially unaffected.
  • the shunt-connected lamp may be of a higher voltage type and may be connected directly across the primary winding of the transformer, instead of across only a portion thereof. In the specific case under discussion, if the lamp is connected across the entire primary, its rated voltage should be approximately 6 volts.
  • a saturating reactor l5 the direct current winding of which is included in the plate circuit of one of the radio or intermediate frequency amplifier tubes, or in any other circuit in which the direct current is a function of the amplitude of the receiver signal.
  • a light source 'l'l maybe connected in series with the secondary winding of the power transformer, While another source 19, requiring higher voltage, may be connected in shunt thereto.
  • the principle of operation of the modified circuit is essentially the same as explained in connection with Fig.
  • the lamp 'i9 being equivalent to the lamp 5I, while the lamp 11 functions in a manner analogous to the operation of the lamps 45 and 41.
  • the saturating reactor 15 will not permit as sharp an indication of the tuning as the system previously described and in general the system is not as iiexible in its application.
  • the winding of the saturating reactor 15 may be tapped and a light source 80 be connected thereacross, as indicated by dotted lines in the drawing.
  • the positions of the tuning indicator lamps are, of course, optional with the manufacturer of a radio receiver. I have found it desirable, however, to so dispose both of the lamps that they serve alternately to illuminate a tuning dial, one of the lamps, through any desired arrangement of color screens, or the like, being utilized to indicate that the set is exactly tuned in, while the other lamp provides light to assist in the tuning operation.
  • carrying frequency indicia, or the like I prefer to dispose the light 5
  • the several light sources may be arranged in any other desired manner, they may be colored, or
  • a receiver comprising my improved tuning indicator that it offers many advantages not heretofore obtainable. For example, it is quite easy to visually tune in any desired station, even though the loudspeaker is not audible, which is desirable in the event that the incoming signal is being reproduced in a situation distant from the point at which the receiver itself is located.
  • the visual tuning indication is also much more exact than the indication of tuning given by the quality and amplitude of the sounds reproduced, since the automatic volume control device tends to maintain the volume constant, even though, by reason of inaccurate tuning, the amplitude of the signal impressed upon the second detector is less than it should be.
  • a radio receiver In a radio receiver, a plurality of light sources, means for supplying alternating potentials thereto and means controllable by an incoming signal for varying the intensity of illumination from one of said light sources in inverse ratio to that from another of said light sources.
  • a radio receiver a plurality of light sources, means capable of supplying alternating potentials to said sources, means including a transformer responsive to the condition of sensitivity of said receiver for determining which of said sources receives potential from said energy supply.
  • a radio receiver means for correlating the sensitivity thereof to the amplitude of an incoming signal, a plurality of light sources, means for supplying alternating potentials thereto and means including a variable impedance in series with one of said light sources and in shunt with another of said light sources, said means being responsive to the condition of sensitivity of the receiver for determining which of said sources gives off the greater light.
  • a radio receiver a light source, alternating potential supply means for energizing said source when the receiver is in syntony with signals from a desired transmitter, a second light source, and alternating potential supply means for energizing said second source when the receiver is not in syntony with signals from the desired transmitter, whereby, through observation of the condition of illumination of said sources, the exactness of tuning of the receiver may be judged.
  • a light source In an amplifier, a light source, an alternating current supply circuit connected to said source, a step-down transformer, the primary winding of which is included in said circuit, a. thermionic device, the space current path in Which is in series With the secondary Winding of said transformer, and signal-responsive means for varying the impedance of said thermionic device.
  • a radio receiver a plurality of light sources, means for supplying alternating potentials thereto, .a turning indication device adapted to be illuminated by said light sources, means for screening certain portions of said tuning indication device from illumination by respectively different ones of said light sources, and means controlled by an incoming signal for varying the intensity of illumination from one of said light sources in inverse ratio to that from another of said light sources.
  • a radio receiver a receiving network, a source of automatic volume control potential therefor, a transformer having a primary Winding and a secondary winding, a tube having an anode circuit connected with said secondary winding whereby said tube is a load upon said transformer, a tuning indicator, a source of light associated therewith, an energizing circuit including at least a portion of said primary winding for supplying alternating current to said light source, means for applying the potential from said .automatic volume control source to said tube to control the effectiveness of the load upon said transformer, and means for adjusting the impedance of said tube whereby signal variations cause the load upon said transformer to vary between limits adapted to cause an indicating change in the illumination of said light source.
  • a radio receiver a receiving network, a source of .automatic volume control potential therefor, a saturatable reactor, a tube having an anode circuit, said reactor being connected with said anode circuit to receive saturating current therefrom, a tuning indicator, a lamp associated therewith, a lamp energizing circuit including at least a portion of said reactor for supplying a1- ternating current to said lamp, means for applying said potential from said automatic volume control source to said tube to control the flow of saturation current whereby to cause an indicating change in the illumination of said lamp.
  • Radio receiving apparatus comprising, in combination, signal-selecting means tunable to receive any signal of specified frequency in a band of frequencies, signal-amplifying means for amplifying the signals thus received, incandescent indicating means connected to said amplifying means for producing variations in light in accordance with the average current flowing through said amplifying means, .and light-diffusing means for rendering readily perceptible small variations in the light produced by said indicating means, indicative of small variations in the tuning of said selecting means.

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US646074A 1932-12-07 1932-12-07 Indicating device Expired - Lifetime US2166674A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
NL39161D NL39161C (enrdf_load_stackoverflow) 1932-12-07
US646074A US2166674A (en) 1932-12-07 1932-12-07 Indicating device
DER89370D DE704870C (de) 1932-12-07 1933-12-06 Schaltungsanordnung fuer optische Abstimmanzeiger von Empfaengern

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US646074A US2166674A (en) 1932-12-07 1932-12-07 Indicating device

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US2166674A true US2166674A (en) 1939-07-18

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US646074A Expired - Lifetime US2166674A (en) 1932-12-07 1932-12-07 Indicating device

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US (1) US2166674A (enrdf_load_stackoverflow)
DE (1) DE704870C (enrdf_load_stackoverflow)
NL (1) NL39161C (enrdf_load_stackoverflow)

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NL39161C (enrdf_load_stackoverflow)
DE704870C (de) 1941-04-09

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