US2204398A - Tuning indicator system for radio receiving apparatus and the like - Google Patents

Tuning indicator system for radio receiving apparatus and the like Download PDF

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Publication number
US2204398A
US2204398A US156676A US15667637A US2204398A US 2204398 A US2204398 A US 2204398A US 156676 A US156676 A US 156676A US 15667637 A US15667637 A US 15667637A US 2204398 A US2204398 A US 2204398A
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Prior art keywords
frequency
signal
resistor
tuning
transformer
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Expired - Lifetime
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US156676A
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English (en)
Inventor
George L Beers
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RCA Corp
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RCA Corp
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Priority to BE429453D priority Critical patent/BE429453A/xx
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Priority to US156676A priority patent/US2204398A/en
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    • 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

  • the present invention relates to tuning or resonance indicating means for radio receiving apparatus and the like, and more particularly tuning indication means-which is adapted to provide resonance indicationin comparison with a condition of nonresonance, whereby receiving ap paratus provided with such indication means may be tuned more accurately than has heretofore been possible.
  • tuning radio receiving apparatus it is desirable to tune xactly to-reschance in order that the fidelity of 'reception'may not be impaired, and, for this purpose, as a tuning aid, accurate visual means sharply responsive to a received signal is highly desirable.
  • Substantially all radio receiving apparatus is provided with automatic volume control means.
  • automatic volume control devices tend to maintain the signal applied to the second detector and therefore the volume or audio frequency output level substantially constant over an appreciable frequency range at each side of resonance, with the result that it is di-flicult to tune by car a receiver having sucha control.
  • radio receiving systems that shall give an indication of the direction in which the tuning ele-.
  • a phase discriminating net-' work in connection withtuned coupled high frequencycircuits, is arranged to provide a control potential which is positive when the receiving system is tuned to one side of resonance, and negative when tunedto the other side, the magnitude of the potential increasing sharply as the tuningis varied from 'thej;point' of resonance.”
  • FIG. 1 Ba schematic circuit diagram 'of a tuning indication system embodying the invention
  • Figure 2 is a modification of thecircuit' of Fig. 1', arranged to provide signal detection and amplification with automatic volume control in addition to tuning indication
  • Figure 3 is a modification of the circuit of Fig. 1 arranged'to' utilize radio frequency impulse in' the control of the indicating device. 7
  • the rectangle firepresents any suitable receiving system' having tuning means represented at 6.
  • the receiving system may be considered as including a radio frequency amplifier, first detector and oscillator as indicated;
  • the signal channel' of the receiving system following the first detector comprises an intermediate frequency amplifier tube 1 connected with an intermediate frequency input transformer 8 and having an output circuit l3 coupled to the primary winding I0 of a second intermediate frequency coupling transformer 9.
  • the secondary is divided into two equal winding sections II and I2, whereby it is adapted to be connected into a phase discriminating network of the type shown, described and claimed in my copending application, Serial No. 134,105, filed March 31, 1937, for High frequency signal responsive control" system, and' assigned to the same assignee as the present application, for deriving control potentials through a diode rectifier device 23.
  • the primary winding is tuned to the intermediate frequency by a shunt adjustable tuning capacitor i5, and the secondary is similarly tuned by a shunt adjustable tuning capacitor Hi.
  • tuned primary and secondary windings provide two coupled tuned circuits I! and I8 resonant at the same frequency.
  • the windings II and I2 are arranged to form a continuous winding inductively coupled to the winding IE! and the high potential or outer terminal ends thereof are connected to the secondarytuned circuit terminals, indicated at H! and 20, and to the anode electrodes 2
  • and 22 are associated with a common cathode 24 of the device 23 which cathode is connected through a lead 25 with the tuned primary circuit ll.
  • the anode connection includes the positive anode supply lead 14.
  • the secondary winding sections are each connected with the lead l4 and a secondary center tap terminal 26 through two resistor sections 27 and 28. The latter are connected in series between the adjacent terminal ends of the secondary sections H and i2 through leads indicated at 29.
  • the resistor sections are provided with intermediate frequency bypass capacitors 30 and 3
  • the signal or carrier potential applied between the cathode M and the center tap 2% of the output resistors 2'! and 28, is derived from the primary or input circuit i'i through the connection lead 25'between the cathode, Z4 and the high potential terminal 26A.
  • the opposite side of the tuned primary winding is bypassed to the negative B supply terminal 52 and to ground 13 through the bypass capacitor M.
  • the center tap 26 is bypassed to ground through the lead M and the bypass capacitor 44.
  • Direct current control potentials are derived from the resistor output terminals 32 and 33 through output leads indicated at 34 and 35.
  • the rectified current flowing through the resistor section 27 will be equal and opposite in direction to that flowing through resistor sec tion 28 and the voltage between the terminals 32 and 33 will be Zero.
  • the rectified current flowing through, the resistor section 2? will be equal and opposite in direction to that flowing through resistor section 28 and the voltage between the terminals 32 and'3t will be zero.
  • both the primary and secondary voltages are applied to the double diode and these voltages are 90 out of phase, as will be obtained if the signal applied to the transformer has the frequency to which the transformer is resonant, then the signal voltages applied to the two anodes will still be equal and the rectified currents flowing through the two resistor sections will be equal and opposite and the voltage between terminals 32 and33 will be zero.
  • the phase relation between the primary and secondary voltages will no longer be 90 and the signal potentials applied to the two anodes will not be equal and a difference in potential will exist between the terminals 32 and 33 because the rectified currents flowing through resistor sections 2! and 28 will be unequal.
  • the voltages applied to the anode 2i by the primary of the transformer is in phase with the voltage applied to this anode by the secondary of the transformer, the voltages applied to this anode will then. add and if they are equal the anode signal potential will then be twice the value obtained when only the secondary voltage is applied to the double diode. This will cause a corresponding increase in the rectified current flowing through resistor 28.
  • the signal potentials applied to the anode 22 will be 180 out of phase and if they are equal in magnitude, the sum of the voltages on this anode will be zero. Therefore, no current will flow through resistor 2'! and consequently no drop in potential will occur across this resistor.
  • the intermediate frequency amplifier is preferable for the-reason that the latter operates at a fixed frequency and includes fixed tuned circuits at the various interstage transformers.
  • a pair of "coupled tuned circuits already existing in the signal channel of the receiver'and operating at the same frequency may be used to derive two potentials at the same frequency, having a phase relation which varies as the signalapplied thereto tends to; vary on either side of the predetermined intermediate frequency.
  • a phase discriminating network which provides a differential direct current voltage which-varies in, magnitude and'polarity as the frequencyof the received signal varies above or below resonance.
  • the cathode ray beam maybe adjusted toprovide a'figure'or"pattern' omthe screen 4
  • the .'oriance i'sbbtained,the" figure may be a circle or spot in thecenter of the tube and, for off-resonance condition, may change to an ellipse formed on ione side or the other of the tube, thereby producing one form of indication for resonance and a differing indication for off-resonanceJtunmary or anode circuit is returned to the center tap-of the resistorsx2'l and 28 and the cathode is connected therewith through the primary so that the rectifier circuit is at anode B potential.
  • This .circuitarrangement permits the deflector plates to operate at positive B potential with direct connection with the output resistors 21 and28.
  • the device 23 in which the rectifier elements are'provided is also a double diode triode tube as indicated, having a control grid 45 and an output anode 46
  • the device may be arranged to provide automatic volume control' bias by con- 'necting a resistor 41 between the control grid and lead I4 and connecting an automatic volume control lead 49 to the grid end of resistor 41, as
  • a suitable intermediate frequency bypass capacitor 50a is provided across the automatic volume control resistor 41.
  • Signal output potentials may-then be derived from -the secondary circuit between the terminal 26 and the terminal 32.
  • Audio frequencyor modulation potentials may: be derived from the resistor 41.
  • the value of the capacitor 5011 should be such that it provides an effective jb-ypass at intermediate frequencies 5 without appreciably attenuating the audio frequency potentials in the desired'range of operation.
  • FIG. 2 A circuit for deriving signal potentials and automatic volume "control potentials is also shown in Fig. 2, to which attention is now directed.
  • Fig. 2 like parts as in Fig. 1 are designated by the same reference numerals.
  • the doublediode rectifier is provided by a tube 50 which may be of the type known as an RCA 6H6 having two anode electrodes 5
  • and 52 are connected with the terminals I9 and 20 ofthe tunedsecondary circuit 18 which comprises the secondary winding sections I l and I2 and the shunt tuning capacitor Hi.
  • the resistor sections 21 and 28 are included
  • Output leads 34 and 35 are connected with output terminals 32and 33 on the resistors and the lat: ten are provided with bypass capacitors 3B and 3
  • the output anode circuit 13 of the amplifier I is connected withthe 'primarywinding Ill which is provided witha shunt variable tuning-capacitor 15 to form the tuned primary circuit I1, and the latter is coupled to thecathode 53 through a coupling capacitor '55 in conjunction with the coupling resistor 55 v
  • the operation of the circuit of Fig; 2 is similar to that of Fig. 1 and the tuning indicator device is connected with the output resistor comp-rising the sections 2'! and 28 in a similar manner to the cathode ray tube of Fig. 1.
  • the tuning indicator device is an electrical meter indicated at H having a movable pointer 12 which moves over an indicating scale is on either side of a zero position in which it is shown at 14.
  • the meter is connected to the leads 34 and 35 to receive the differential potential from the output resistor 21-23 and the indicator moves to the rightor left as the potential increases from zero in either direction depending upon the polarity of the terminals 32 and 33, one with respect to the other.
  • the derivation of the variable potential is the same as in the circuit of Fig. 1 except that the cathodes 53 are conductively connected back to the center tap 26 through the primary circuit by way of the coupling resistor 55 with which the primary is coupled in shunt relation through the coupling capacitor 56, thereby permitting grounding of the secondary circuit.
  • a choke coil may be substituted for the risistor 55 if desired.
  • ⁇ my suitable polarized indicating device may be used in connection with the leads 3t and 35 to respond to the signal variable potential.
  • the circuit has the advantage that the modulation or audio frequency component of the received signals may be applied to an output ampliflying circuit through a second detector comprising a diode rectifier 59 connected with onehalf of the secondary winding.
  • a cathode 6i! is connected with the terminal 25 of the tuned circuit l8, and the anode electrode 6
  • the output resistor is provided with a suitable by-pass capacitor 64.
  • the intermediate frequency carrier wave received in the tuned circuit I3 is applied in part to the rectifier 58 across one-half of the secondary winding l2, and the modulation and direct current component thereof appear across the output resistor 62.
  • the output resistor 62 may be connected between the control grid 65 and the cathode 66 of an audio frequency amplifier 61 to apply a biasing potential thereto and audio frequency signals simultaneously, whereby the amplifier is diode biased by the signal.
  • the audio frequency output is derivedfrom an output lead 68 in connection with the output anode 69.
  • the cathode 66 is connected with the ground lead 63, as indi. cated.
  • Automatic volume control potentials may be derived from the output resistor 62 through an output lead indicated at H1 and applied to any suitable portion of the receiving system for automatic volume control purposes, in any wellknown manner.
  • can be eliminated so that a single coil can be substituted for windings II and I2.
  • tuning indication system has been shown and described in connection with an intermediate frequency amplifier, it may be applied to other portions of the radio receiving system wherein two circuits are provided which operate at the same signal frequency and which provide signal voltages which vary in phase in response to off-resonance tuning.
  • the tuning indication system is at present preferred in connection with the intermediate frequency amplifier, since this connection permits existing apparatus to be utilized to advantage.
  • a radio signal receiving system the combination of means for tuning said system to resonance with a received signal, means providing two substantially equal signal potentials in response to a received signal, said potentials having the same frequency and a predetermined phase relation to each other when said receiving system is adjusted to resonance with said received signal, means for converting a variation in frequency of said received signal into a variation in phase between said potentials, said first and second-named means including the primary and secondary of a coupled tuned circuit intermediate frequency transformer through which said received signal is conveyed, means for converting said variation in phase into a controlling potential for said system, said controlling potential being variable in response to said phase variation in magnitude and direction of variation from a zero value, indicating means responsive to changes in the magnitude and direction of varir ation of said potential, whereby resonance and off-resonance conditions of tuning of said system are provided thereby, a signal rectifier connected with said first-named means for rectifying at least a portion of one of said signal potentials, and means for deriving the modulation component of said signal and automatic volume control potentials
  • a superheterodyne receiver the combination with tuning means therefor, of an intermediate frequency amplifier, a coupling transformer for said amplifier having a tuned primary circuit and a tuned secondary circuit resonant at the same intermediate frequency, said secondary winding having two tuning inductance sections, a resistor element having a center tap connected between said sections, a rectifier device having a cathode and two anode electrodes associated therewith, said anode electrodes being connected with the terminals of said secondary circuit and said cathode being connected through the primary circuit with said center tap on the resistor element, means for deriving difierential direct current potential from said resistor element in response to received signals, tuning indication means responsive to the magnitude and polarity of said potential connected with said resistor element,'and mans-for deriving audio frequency signal and automatic volume controlpotentials from at least one portion of said secondary circuit.
  • a radio receiving system the combination with means fortuning said system to resonance with a signal, of a signal amplifierprovided with two tuned coupled signal conveying circuits, said circuits being resonant at substantially the same signal frequency, said tuned circuits including the primary and secondary windings of a tuned transformer device, a rectifier having a cathode connected through the primary winding with acenter tap on the secondary winding and having a pair of rectifier anode electrodes connected with the terminals of the secondary windings, an output resistor for said rectifier, a cathode ray indicating device having a pair of beam deflecting electrodes connected with said output resistor, an
  • audio frequency detector connected with one of said windings, and means for deriving audio fre-f quencyand automatic volume control potentials from said last named detector.
  • a superheterodyne receiving system the combination with an intermediate frequency amplifier, of an in'terstage coupling transformer therefor having a tuned primary and a tuned secondary winding responsive to the same intermediate' frequency, apair of resistors interposed in the secondary providing a center tap therefor, a rectifier having a cathode connected through said primary winding with said center tap and having a pair of anodes connectedwith the terminals of the secondary, a cathode ray indicating tube having at least one pair of beam deflecting electrodes connected with one of said windings to receive a differential controlling potential "therefrom responsive to a variation in frequency of a signal,
  • a rectifier device connected with a portion of the secondary winding and having an output resistor, and an audio frequency amplifier connected with said resistorto receive output signals therefrom GEORGE L. BEERS.

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US156676A 1937-07-31 1937-07-31 Tuning indicator system for radio receiving apparatus and the like Expired - Lifetime US2204398A (en)

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BE429453D BE429453A (enrdf_load_stackoverflow) 1937-07-31
US156676A US2204398A (en) 1937-07-31 1937-07-31 Tuning indicator system for radio receiving apparatus and the like

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