Патент USA US2136665код для вставки
Nov. 15, 1938. A. w. BARBER- _ 2,136,665 , RADIO TUNING INDICATION Filed Feb. 118, 1956 Q2 FESRESELECTOR " ' AND RADIO FREQ. ” ‘ AUDIO DETECTOR AMPLIFIER. ' L AMPLIFIER _ Ii 7 I. 59.1. _ SPEAKER SPECIAL ‘ ‘ ‘ DETECTOR DIRECT“ CURRENT? AMPLIFIER - LAMP 11v VENTOR ' 2,136,665 Patented Nov. 15, 1938 ‘ UNITED STATES PATENT ()FFICE ‘ ‘ ' 2,136,665 ’ ' _ ' i ‘ RADIO TUNING INDICATION Alfred W. Barber, Flushing, N. Y. Application February 18, 1936, Serial No. 64,517 4' Claims. ‘ (oi. 250--4o) operation the long time constant diode load This present invention of mine concerns im provements in tuning indicator methods and charges up as the receiver is tuned thru a signal means, adapted for use in radio receivers and to a maximum voltage point the value of which ‘ the like. depends on the signal strength. Since the time ‘ One object of my invention is to provide a tuning indicator which operates to indicate cor rect tuning in radio receivers and the like. An. other object is to provide such an indicator which constant is large, the circuit holds this voltage. 5 as the receiver is tuned beyond the signal. On the other hand, the short time constant circuit gives‘a sharp indication regardless of the strength 10 of the signal being tuned in. Still another ob ject as the signal is tuned out again. Thus one volt age indicates the maximum signal strength and the other indicates the instantaneous'signal or tuning point. If an indicator is attached which operates when both voltages are equal, the indi cator will show exact tuning as exact tuning exists only when both diode voltages are equal at max 15 is to provide a tuning indicator‘ which operates by means of a lamp which lights when a signal is correctly tuned in and operates by automatic electrical means. In continuously tunable radio receivers em ploying automatic volume control, the point of exact tuning is _‘difficult to locate by ear, due to the fact that in passing thru a signal the auto matic 'volume control system follows the signal 2 O variations tending to keep the loud speaker out put constant. In order to make accurate tuning possible a number of different indicators have been devised. The most Widely used indicators are meters or lamps actuated by plate current 25 changes in the ampli?er tubes controlled by the . automatic volume control. Correct tuning is in dicated by a minimum ampli?er ‘tube plate cur rent or maximum plate voltage due to the action of the automatic volume control voltage. These systems operate much better on strong signals than on weak ones and may even ceaseto operate on signals below a certain level. The apparent sharpness of the indication also varies with signal strength, since moving say 5 kilocycles on a strong station may actuate an indicator much further than 5 kilocycles change on a, Weaker station. charges up with the signal but discharges again imum response. The appended claims set forth, in particular, the novelfeatures to be found in this invention. The following description, however, when taken in . connection with the drawing, will serve to set forth the theory and mode ofroperation of my invention. _ In the drawing- , ' Fig. 1‘ shows 'a'block diagram of the general form of my invention. _ 25 vFig. 2 ‘shows a circuit of an indicating system embodying my invention. ‘ Fig. 3 shows a circuit equivalent to one mode of operation of the circuit of Fig. 2. Fig. 4 shows a circuit equivalent to another 30 mode of operation of the circuit of Fig. 2. Fig. 5 shows a circuit of another form of my in vention.‘ V Fig. 6 shows curves of voltages generated by various forms of my invention. a 35 The block diagram shown in Fig. ‘1 indicates the general form of my tuning indicator system. A conventional automatic volume control receiver In my copending application for Letters Patent entitled “Recti?er circuits” ?led January 30, 1 936, and bearing Serial No. 61,457 I have shown a - system is indicated including a “pre-selector and 40 recti?er circuit having some unique properties. radio frequency ampli?er”, a “detector”, an This recti?er circuit is used in my present tun “audio ampli?er” and a “loud speaker”. At the ing indicator system. output of the “radio frequency ampli?er” and in My present system‘ of tuning indication over- ‘ comes the dif?culties pointed out above since the 45 indicator‘ flashes on at correct tuning giving a Very sharp indication and operates with equal sharpness on‘ strong ‘or weak signals. I employ two diode circuits rectifying the carrier frequency output of the radio receiver. One diode circuit parallel with the “detector” is connected‘ my “special detector” generating an indicator con trol signal. The generated control signal is am- 45 pli?ed by a “direct current ampli?er” and then actuates the “lamp” or other indicating device. While the invention is not limited by the point of connection of the “special detector” this will be 0 has a long time constant load circuit and the other the usual point as the radio or intermediate ‘frequency voltage is a maximum at this point. Fig. 2 shows a circuit diagram of one form of ful output is the difference between the voltages my tuning indicator disengaged from the rest of generated by the two diodes and it may be ampli fled by a direct current ampli?er, and used to the receiver. It embodies the double diode recti ‘diode a short time constant load circuit. The use 55 actuate a lamp or other indicating device. In ?er tube I, which may be two separate diodes as 55 2 2,136,665 well, the direct current ampli?er tube 2, and the indicating lamp 3 which may be some other type of indicator such as a meter or light shutter. The unrecti?ed voltage is introduced into the diode circuit by means of the transformer having a primary 4 and a magnetically coupled secondary 5. This transformer may be a part of the re ceiver or may be a branch circuit for the tuning indicator and capacity coupling may be used to The pri mary will in general be connected in parallel with 10 coil 5 doing away with the primary 4. the regular receiver detector as shown in Fig. 1. The alternating current voltage appearing across coil 5 is impressed on the two diodes, thru the 15 independent load circuits consisting‘of’ resistor 6 by-passed by condenser ‘I and resistor 8 by passed by condenser 9. The diodev cathodes I0’ and resistance 8 in parallel is low enough so that the voltage across condenser 9 follows the signal variations due to tuning, the net voltage across points 2| and 22 will ‘indicate the tuning condi tion. If the tuning is carried to a point where no signal is picked up, the voltage across condenser 9 drops to zero and the point 2I is positive with respect to ground by the voltage of battery 20. Now if the tuning is returned to the signal, as the signal is tuned in the voltage across condenser 9 10 builds up and the net voltage between point 2I and ground drops. When the signal is again tuned into maximum response, the voltage across condenser!) equals the voltage of battery 20 and the net voltage between point 2I and ground is ZerO. ' t r ' While not limited to these values, I have found and II are connected together and to one end of ‘ that in'ge'neral the time constant of condenser ‘I input coil 5. A common cathode may be used in parallel with resistor 6 should be greater than 20 in place of cathodes I0’ and II. The resistor 6 one second and the time constant of condenser 9 20 condenser 'I load is in series with coil ‘5 and in’para'llel with resistor 8 should be less than diode anode I2 and the resistor 8 condenser 9 one second for the best operation of my system. load is in series with. coil 5 and the other diode When the actual circuit of Fig. 2 is used, the anode I3. The diode anode I2 is connected to condenser ‘I charges upon the ?rst excursion thru ground or reference potential point G and the the signal establishing the reference voltage recti?ed output is taken off between anode I3 and ground or reference potential point G. Some of the properties and uses. of this circuit are pointed out in my previous application referred to above. The present description will be limited to its functions and characteristics-as used in my tuning indicator. . . " » The voltage difference between anode I3 and ground is impressed on grid I4 of the direct 35 coupled ampli?er tube 2 by direct connection. Tube 2 may be a multi-grid tube but is shown as a triode havingcathode .I5, grid I4 and plate I6. ,A steady'grid bias'is impressed on tube 2 by bat tery E0 connected between ‘cathode I 5 and ground 40 G; The indicator part of the circuit consists of a neon or gas ?lled glow lamp 3 parallel fed from plate I6 and alternating current source ‘I'I thru variable resistor I8. The alternating - current ‘source Il may bethesecondary of a transformer 45 with primary I9 connected to the alternating current power lines. In‘operation the ‘resistor I8 and the plate resistance'of'tube 2 act to divide the‘voltage from secondary 11. If the grid I4 is made more positive or less negative the plate re sistance of tube 2 decreases, There will be a crit 50 ical biason grid I4 such‘ that lamp 3 just lights on the peaks of the alternating current wave for particular values of resistor I8 and voltage across secondary I1. If EC is made equal to this critical 55 bias and the only voltage’ placed on grid I4 is positive with respect to ground, lamp 3 will only light when zero voltage is placed on grid I4. ~ The operation of the indicator depends on the pro duction of zero net voltage by the recti?er when 60 the receiver is exactly tuned. ‘ Fig. 3.is useful in explaining the operation of Fig. 2. "If the time constant of resistor 6 shunted by condenser ‘I is made long,,increases in input signal will build up the charge in condenser ‘I but decreases in signal will leave the charge to ‘discharge slowly thru resistor 6. If the circuit of Fig. 2 is attached to a radio receiver and the receiver vis tuned thru a signal, the voltage across condenser ‘I will build up to a maximum value equivalent to battery 20 and the voltage supplied to grid I4 from the recti?er drops to zero only when the tuning is restored to the point giving maximum response. As explained above the lamp 3 is thus caused to light when no external bias is fed to grid I4 which takes place only at exact tuning of the receiver. Fig. 6 shows curves “of the voltages produced in the recti?er circuits of Fig. 2 upon tuning thru a signal. Curve a represents the steady positive 35 reference potential established in condenser l upon'tuning thru a signal. The difference be tween curves 0 and b is the voltage across con denser 9 upon tuning back thru the signal and curve I) is the net voltage passed on to grid I4. 40 This shows that this net voltage is zero at h which point is the point of resonance for the tuning system. For the purpose of allowing reasonable tolerance in the system it may be necessary to allow lamp 3 to light whenever the external volt 45 age applied to grid l4’ falls below say 0.5 volt. These limits are indicated on Fig. 6 by line e at 0.5‘ volt or whatever arbitrary voltage is chosen. The intersection of c with b shows that under these conditions lamp 3 will light from g to 7' 50 which may for instance correspond to 1000 cycles 'either'side of exact tuning. Fig. 5 shows a circuit in which lamp 3 is con nected in series with the ampli?er tube plate. The recti?er I is inverted so that the load circuits are in the diode cathode circuits. This reverses the polarity of the recti?ed voltages with re spect to ground when cathode I0 is grounded and the output is taken off between cathode I I and ground G. If, as before, the time constant of re 60 sistor 6 and condenser ‘I in parallel is made long, a reference potential diiference c’ as shown in Fig. 6' will be established across condenser ‘I. Upon tuning thru a signal the net voltage between cathode II and ground G will follow curve (1 65 and the net voltage will be zero at exact tuning. With lamp 3 in series with the plate I6 of tube replaced by battery 20 with the negative end 2 and in parallel with resistor I8, the supply voltage EB plus the alternating current voltage ‘across transformer secondary I‘I divides between 70 resistor I8 and the internal plate resistance of tube 2. If bias E0 is made such that lamp 3 just lights with zero voltage supplied to grid I4 from the recti?er circuit, lamp 3 will be extinguished grounded. If the time constant of‘ condenser 9 as soon as the plate resistance is increased, since 75 770 proportional to the amplitude of the signal and ‘will hold this’ voltage. Fora short time there .after the recti?er circuit acts like the circuit in Fig. 3 in which the voltage across condenser ‘I is \ increasing the plate resistance lowers the voltage drop across the resistor 18 and lamp 3. The plate resistance increases in tuning over curve dexcept at exact tuning. Thus the lighting of the lamp Ci indicates exact tuning. The recti?er part of Fig. 2 can be reversed mak ing the series lamp connection possible simply by reversing the long and short time constant loads. This is shown in Fig. 4 where the battery 20 equivalent of the long time constant circuit is in series with anode i3 and the resulting voltage is negative except at exact tuning. Similarly the recti?er part of Fig. 5 may be reversed permitting the parallel fed indicating lamp with this recti?er connection. The various systems may also be set-up so that at a critical bias the lamp goes out and the bias from the recti?er keeps the lamp lighted except at exact tuning. 3 . 2,136,665 This is accomplished 20 by interchanging the series or parallel lamp con nection with the parallel or series connection. In this case the lamp extinguishes at exact tun— , mg. In general gas ?lled glow lamps which I pro pose as suited to this tuning system require a higher voltage to break down than to extinguish. For instance a lamp may not light until the voltage across it is 100 volts but upon reducing between the two said unidirectional voltages is less than a predetermined amount. 2. In a tuneable carrier wave receiver, the combination of a tuning lamp, a thermionic vacuum tube ampli?er including a grid, a cath ode and a plate and a recti?er including two rectifying circuits, means for applying carrier voltage to said recti?er, means for producing a voltage proportional to the peak unmodulated carrier voltage applied to said recti?er and means 10 for maintaining said voltage substantially con stant for a predetermined period of time greater than the normal time required to tune said re ceiver thru a desired carrier in one rectifying circuit of said recti?er, and means for produc ing a second voltage proportional to the instan taneous peak unmodulated carrier voltage ap plied to said recti?er in the other rectifying cir cuit of said recti?er, means for applying a volt age proportional to the di?erence between the 20 two said recti?ed voltages to the grid'of said ampli?er and a series circuit in the plate cir cuit of said ampli?er including said lamp and a source of alternating current whereby said lamp operates when said voltage difference is 253 less than a predetermined amount. - 3. In a carrier wave receiver, the combination of a gaseous glow lamp, receiver tuning means, a the voltage, the lamp may remain lighted until , thermionic vacuum tube ampli?er including at the drop across it falls to 80 volts. A lamp of this type in my tuning system, with direct current only on the ampli?er tube plate, will show a drag in the direction of the tuning due to this difference between ignition and extinc tion voltage. By using an alternating current Voltage in series with the lamp having an ampli tude greater than the difference between ig nition and extinction voltages the lamp is turned 40 on and o? at an invisible rate preventing any drag effect. If the tuning is carried to a point ' below the ignition condition, the alternating cur rent turns the lamp off and it does not ignite again until the tuning is returned to a favor able point. Thus the visible indication follows the ignition condition curve regardless of the lag or drag eifect in the lamp. While I have described only a few systems whereby my invention may be carried into effect and have pointed out a few possible variations, it will be apparent to one skilled in the art that many modi?cations are possible without de parting from its spirit and scope as set forth in the appended claims. What I claim is: I 1. In a carrier wave receiver, the combination of receiver tuning means, a tuning indicator and a recti?er comprising two rectifying circuits, means for applying carrier voltage to said recti ?er, means for producing a unidirectional volt 60 age proportional to the maximum amplitude of a carrier voltage applied to ‘said recti?er and means for maintaining said unidirectional volt age substantially constant for a predetermined period of time, means for producing a second 65 unidirectional voltage proportional to the in stantaneous amplitude of said carrier voltage applied to said recti?er and means for operat _ ing said tuning indicator when the difference least a grid, a cathode and a plate, and a recti 30 ?er including at least two ‘rectifying circuits, means for applying carrier voltage to said rec ti?er, means for producing a voltage propor tional to the amplitude of the carrier applied to said recti?er at receiver resonance with said 85 carrier and means for delaying the decay of this voltage so that its decay lags substantially behind the decay of carrier voltage applied to said recti?er due to tuning said receiver away from said carrier in one rectifying circuit of 40 said recti?er, means for producing a second voltage proportional to the instantaneous ampli tude of the carrier applied to said recti?er in a second rectifying circuit of said recti?er, means for applying a voltage proportional to the dif 45 ference between said two recti?ed voltages to said grid and means for operating said glow lamp from the plate of said ampli?er when the differ ence between the two said recti?ed voltages is less than a predetermined amount. 50 4. In a carrier wave receiver, the combination of a gaseous glow lamp tuning indicator, an ampli?er tube including at least a grid, a plate and a cathode and two diode recti?ers, a load circuit having a time constant greater than one second in series with one of said diodes and a load circuit having a time constant of a small fraction of a second in series with the other of said diodes, a connection between one end of each of said load circuits and a common in 60 put circuit, a connection between the remain ing end of one of said load circuits and ground and a connection between the remaining end of the other of said load circuits and the grid of said ampli?er, a connection between said 65 plate and said lamp whereby said lamp glows when said receiver is adjusted to maximum re sponse with a carrier wave. ' ALFREDW. BARBER.