US2483409A - Tuning arrangement for thermionic valve circuits - Google Patents

Tuning arrangement for thermionic valve circuits Download PDF

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Publication number
US2483409A
US2483409A US509211A US50921143A US2483409A US 2483409 A US2483409 A US 2483409A US 509211 A US509211 A US 509211A US 50921143 A US50921143 A US 50921143A US 2483409 A US2483409 A US 2483409A
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United States
Prior art keywords
tuning
current
circuit
valve
grid
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Expired - Lifetime
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US509211A
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English (en)
Inventor
Gold William Alexander
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International Standard Electric Corp
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International Standard Electric Corp
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03J—TUNING RESONANT CIRCUITS; SELECTING RESONANT CIRCUITS
    • H03J7/00—Automatic frequency control; Automatic scanning over a band of frequencies
    • H03J7/02—Automatic frequency control
    • H03J7/16—Automatic frequency control where the frequency control is accomplished by mechanical means, e.g. by a motor
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G5/00—Tone control or bandwidth control in amplifiers
    • H03G5/16—Automatic control
    • H03G5/24—Automatic control in frequency-selective amplifiers
    • H03G5/26—Automatic control in frequency-selective amplifiers having discharge tubes

Definitions

  • the present-invention relatesto tuning ar rangements for electrical signal transmissionfsystems,and concerns-particularly the tuning of any number-.of stagesvin such a-system..to..a signal wave of a particular frequency.
  • a radio transmitter for-example, :it is usually necessary to tune one or more thermionic valve stages to the frequency. of the-masteroscillator; and furthermore, ⁇ the aerial circuitvmay ⁇ need to be similarly tuned. While 'the invention will' be l' described in its application to a radio transmitter it is. applicable to-any transmission system having stages which need tuningf toa signal' frequency, and the ultimate load isnot necessarily anaerial.
  • the invention is concernedwith automaticV means for performing the tuning,l and mayv comprise two operations, in the first of which some or all -of the amplifying stages-.are ⁇ given a-simul taneous rough tuninl-, ⁇ and in the second each stage is separately givenl a .nal accurate tuning.
  • the tuning arrangements are controlled by the variations of a rectied current lin avvalve or rectiiier which passes through a maximum Orminimurn-asthe tuning is varied through theresonance point.
  • lan arrangement for adjusting a tunable circuit to resonate at the frequencyof an applied'signal wave which comprises an electromagnetic device adapted to vary a reactance forming Vpart of the tunable circuit under theV controll of-a current derived from a thermionic valve or rectier, which current is adapted to vary according to the instantaneous resonance frequency of the tunable circuit and to attain a maximum ora minimum valuewhen the tunable circuit -is in'V resonance with the signal frequency.
  • Fig. 2a shows the application of the diode control of Fig. 3 to the'circuitlof Fig. -2.
  • Fig. 4 shows a control amplifier Which-may be used with any of the circuits shown in Figs. l, 2 or 3;
  • Fig. 5 shows a diagram of a switching arrangement for facilitating the tuning of a number o amplifying stages
  • Fig. 6 shows a relay circuit which may be employedl for preliminary tuning adjustments.
  • Fig.'1v showswtwo stages of a thermionic valve amplier forming .part of. afwave v.transmission system, for example, a power amplier ⁇ ina radio transmitter.
  • .It will be assumed that ⁇ the valve V2 ati least is operated under class ⁇ C conditions, that-is,-r the control grid is negatively biassed well beyond thecut-01T point :and the amplitude of the signal applied to the control grid is such that it iis rdriven positiyeybyl the -positive half waves.
  • the resulting grid current will therefore increase asthe amplitude' of theapplied signal increases, and vice-Versa.
  • the two valves V1 andV2 are provided withk conventional auxiliary arrangements comprising appropriate impedances Zg for connecting the control grids to suitable biassing ⁇ sources represented by batteries GB.
  • the condensers K are coupling condensers of suitable. capacity.
  • The-anode current ofthe ValvewV 1 is supplied from; the high-tension; source I-IT-ithrough a parallel tuned circuit comprisingv an adjustable condenser C and an inductance L which may also bev adjustable as indicated.
  • the valve V2 may be supplied-,by a similar.l arrangement shown but not designated.
  • the 'idevice M is therefore effectively controlledbythe grid current.
  • Thisffdevice may be of any suitable type; it may, for example, be similar in principle to one of the well 1. known types of direct-current indicatingr meters, the moving coil or armature being adapted to. rotate a movable vane or vanes or the condenser ⁇ C, or otherwise to vary its capacity.
  • the device should in addition be provided with means for locking the movement in any position, preferably.electro-magnetically controlled.
  • the function of the device M is to tune the circuit L, C accurately to resonance at the frequency of the wavesrapplied to the control gridcf the valve ⁇ V1 at the terminal IN.
  • a preliminary rough tuning is vfirst carried out manually or automatically by ad'justingin'ductance L and the condenser C, but leaving the circuit slightly mistuned onone ⁇ side-or the other of thesignal frequency according to the manner in which the device M varies the frequency of the circuit L, -C as will be presently explained.
  • the control-ofthe tuning depends on the varia-Y tion of the grid-currentpfthe valveVz. Having given arconstant signalinput atl the terminalgIfN,
  • the grid current will increase to a maximum as the resonance frequency of the circuit L, C approaches the signal frequency from either side.
  • the grid current of valve V2 will increase until the signal frequency is reached and will thereafter decrease. It will, therefore, be arranged so that when the grid current increases it will operate device M in the direction to decrease the capacity of the condenser C so that the frequency change brought about by the movement of device M will tend to drive it in the direction to increase the change.
  • the maximum of the grid current is reached the device M will come to rest and will leave the circuit L, C tuned accurately to the frequency of the incoming signals. It is then locked in the rest position. 1
  • the preliminary rough adjustment must tune the circuit L, C sufficiently near the signal frequency so that the grid current has begun to flow in the valve V2 in order that device M may be able to control the final :i
  • device M must be arranged to control inductance L or condenser C so that the effect of the grid current is to move device M in the direction to improve the tuning.
  • Fig. 2 shows an alternative arrangement wheref by the device M is controlled by the anode current of the valve V1 instead ⁇ of by the grid current of valve V2 (which is not shown in Fig. 2). Assuming that a signal of constant amplitude is applied to the control grid, then the anode current passes through a local minimum value ⁇ as the tuning of the parallel resonant circuit L, C is varied through the resonance point.
  • the anode current passes through the resistance R1 connected in series with the cathode 0f the valve V1 and shunted by the by-pass condenser K.
  • the potential drop across resistance R1 is applied between the control grid and cathode of a reversing valve V3 so that the local minimum may be transformed into a maximum for operating the device M.
  • the resistance r is connected in series with the anode of the valve V3 and operates the device M through the control amplier CA as already desired.
  • the valve V3 does not need to be a power valve and should preferably be operated under class A conditions, suitable biassing arrangements (not shown) being provided by Well known methods.
  • Fig. 3 shows an arrangement in similar principles adapted for adjustment of the aerial matching coils in a radio transmitting system, which includes automatic means for carrying out the preliminary as well as the nal adjustment.
  • the aerial A is connected to earth through an inductance coil L1 adapted for the preliminary adjustment, a second inductance coil L2 adapted for the final adjustment, and also through the secondary winding of an output transformer T the primary winding of which is connected to the last y stage of the power amplifier of the radio transmitter, (not shown).
  • the coil L1 is adjusted by an electric motor D which controls a movable contact d on L1 (or which may change the inductance in any other convenient way).
  • the motor D is driven from a power supply connected to the terminals DS, through a starting switch SS.
  • the aerial A is connected to earth through a diode Vv connected in series with a resistance r3 shunted by a by-pass condenser K1.
  • a blocking condenser K2 may be included if necessary.
  • the control amplifier is connected as before across resistance T3, and operates the device M in series with a relay RY. M controls the adjustment of L2 in the manner previously described, and is short-circuited by the normally closed contacts fyi of the relay RY; and the motor D is connected to the power supply through the normally closed contacts Tg2 of the same relay.
  • the adjustments of the coils L1 and L2 are to be made, it is first arranged so that coil L2 is set at one end-or the other of its range, and the starting switch SS is closed to connect the power to the motor D. Since the aerial A is initially out of tune, the signals derived from the transformer T will produce only a small rectified current in the circuit of the diode V1. The motor, however, will be adjusting coil L1 in the direction to improve the tuning, and the rectified current will increase until the maximum is reached when the aerial is tuned to the signal frequency. It is arranged so that just about this time, or perhaps a little earlier, the rectified current reaches a value suilicient to operate the relay RY which opens both the contacts fyi and ryZ.
  • inductance L1 is set at the minimum value before the adjustment begins, then the motor adjusts it too high and inductance L2 should therefore be at the maximum setting when device M is short circuited, so that device M may be able to make the necessary reduction in the total inductance.
  • coil L1 is initially at the maximum, then coil Lgrmust be initially at the minimum. It will be obvious that the total range of coil L2 must be such as to cover with sufficient margin the amount of overshoot produced before the motor stops.
  • the control amplier comprises two amplify.
  • the same control 'amplier may an appropriateswitch as shown@ ina Figure 5 which qmally 'open,2andscontrolled by theabove-men-v4 .tioned switch, is iconnected iacross the con-
  • the resistanceRz should have' a high nvalue (for #example .megohms) anduthe capacity of the :condenser v'C1f shoul'dmbe large, (for example ⁇ 1 i znicrcfarad) scthatthe Atime constant'of this ⁇ circuit is suiciently large.
  • ⁇ Impedance of -the vdiode inthe conducting direction is low-sothat thetimeconflstant'of theicoupling network issuiiicientlysmall, 115 ⁇ tlie2anodefpote. ial increases-Will -be almost'im preparatelyAappliedthrough the diode 'V5 to the flcondenser CLIM/hose -potentiaL-.Which is also that .fofitheccntrolfgridI-of -valve Vs, will rise accord- I'lcausilng-the anode current,which operates -ridevicev M1;- toincreasein the same-way.
  • a reversalloi Vthe#grid currentchangelin Valve V2 may also be produced if the signal Waves are 1 modulated orare-'subject to l interruption or in- -lter-ference.
  • the tuning will be arrested-every f timeithis Loccurs, ⁇ but Swillf be resumed directly as lthe gridcurrent increases again, luntil the Y tuning gg-is completed.
  • V4 The'.slowdiscliarge ofthecendenserCi through the resistance R2 will onlyresult in a veryfslight imistuning fwn-ich '-loeing equivalent to affdecrease ofuthegridcurrent of valve V2 will-not'berpassed on through 4the' 'ampliiierso-that it will not initiate fa; complete lmistuning.
  • diode .V2 in Fig. 3 may be replaced -by-s ⁇ ome other-kind of rectier.
  • the preliminary tuning arrangement described with reference to Fig. 3 may be applied with slight modification to the preliminary tuning of all the stages of the system.
  • the system will be assumed to be a radio transmitter but the arrangement will be equally applicable to other systems, which may have some other final load than an aerial.
  • the preliminary tuning elements of all the stages are coupled mechanically to their respective adjustable tuning means such as coil L1 so that they will be simultaneously adjusted by the motor D. It will, of course, be necessary to arrange so that the separate elements are adjusted at appropriate rates so that they will reach the tuning point at approximately the same time, and further, since the same transmitter may be used with a number of diierent aerials, it may be necessary to provide interchangeable units for coil L1 so that a suitable adjustable coil can be selected ior the aerial to be used.
  • the rough and nal tuning can be carried out by the methods explained, by the help of a switching arrangement such as that shown in Fig. 5.
  • a pair of coupled rotary switches is shown having iour positions and an oi position.
  • the switch may, of course, have as many positions as there are stages to tune.
  • the right hand portion of the switch is adapted for connecting the input of the amplifier across the resistance r of the various stages in turn, and L the left hand position is used for connecting the output to the corresponding device M (or to a relay RY1) Position l is used for the rough tuning.
  • the right hand part of the switch connects the input of the amplider CA to the resistance r3 of Fig. 3 and the output to a relay RY1 which controls the contacts T212 of Fig. 3. This relay therefore takes the place ci the relay RY and the device M shown in Fig. 3, the latter being not required for the rough tuning.
  • the right hand portion of the switch carries a third brush B1 which makes contact with a stud F in position l only.
  • Brush B1 and stud F are connected to the points Q1 and Q2 respectively in Fig. 3 and represent the switch SS.
  • the switch is moved to position l, the motor D is started and the rough adjustment is carried out as already explained, the relay RY1 operating and opening the contacts 'r1/2 as soon as the maximum current through the resistance 1'3 is reached.
  • the left-hand portion of the switch also carries a third ⁇ brush Bz which is adapted to make a temporary contact with any of the studs F1, F2, F3 etc. while the switch is passing between the successive positions.
  • the switch may be moved to position 2, by which the control amplifier is connected between the resistance r1 and device M1 of the first stage.
  • the nal tuning then takes place as described. All the other stages may beA tuned in turn by moving the switch one step each time.
  • the position d is allotted to the ne tuning of the aerial A (Fig. 3) and so the studs of the positions i and l on the right-hand side of the switch are multipled together so that the resistance r3 is again used.
  • the left-hand studs are, however, connected to the measuring device M which controls inductance Lz.
  • rihe switch shown in Fig. 5 is only diagrammatic and may be constructed in any desired form; some or all of the switching may be performed indirectly in known manner.
  • the switch can be manually or power driven, and may be provided with appropriate timing arrangements so that sufficient time is allowed on each step for the tuning operations to be completed.
  • the switch may also be provided with contacts (not shown) for energising the locking arrangements oi the devices M.
  • Diode Va is connected with its Ianode to terminal l, and with its cathode connected through the resistance R7 and condenser Cz in parallel to terminal 2.
  • a relay RY2 having a suitable self locking arrangement (not shown) may be connected across resistance Rs and may be adapted to control the contacts r'yZ and ry! (if used) in Fig. 3.
  • a suitable resistance Re may he connected as shown across the terminals l ⁇ and 2 to provide a conducting connection at all times.
  • a class C Vamplifier having a first tube caseros 9 with :a tuned-anode ⁇ circuit, -ian--efutput' tube, and at least one grid in said output tube, the ,output tube being-grid f edfrom the tuned anode circuit of the precedingitubepa motion-and tuning means in'said tuned' anode -circuitsthe-method of :automatically tuning said lanode Ycircuit .to secure maXim-um-inputto said grid, ⁇ which includes the steps of measuring the current tosaid gridcaucing said current to operate said motor irl-proportion to the current, and :operating said-tuning lmeans fromjsaid motorpto' vary the tuning ofsaid anode circ-uit while said grid current incref-ises, ⁇ in a direction tcause still furtherinerease thereof, andi to cease varying'fs'aid tuning -at thecpoint of
  • a motor, aid tuning means in said tuned anode circuit the method of ⁇ automatically tuning said anode circuit to secure maximum input to said grid, which includes the steps of measuring the current iiowing in said anode circuit, obtaining therefrom a secondary current exhibiting la maximum when said anode -current reaches a minimum, causing said secondary current to operate said motor in proportion to the current, and operating lsaid tuning means from said motor to vary the tuning of said anode circuit while said secondary current increases, in a direction to cause still further increase thereof, and to cease varying said tuning at the point of maximum secondary current.
  • an electrical signal transmission :system including a variable reactance and a valve having a tunable anode circuit, said varia-ble reactance comprising part of said tunable anode circuit, means electrically associated with said tunable circuit yfor producing a control current proportionally varying according to the instantaneous resonance frequency oi' said tunable circuit and attaining a critical value at the point of resonance of said tunable circuit with a signal frequency, s-aid control current producing means including a series resistor in said anode circuit and a polarity reversing valve having its grid and cathode connected respectively to the lower and higher potential ends of :said series resistor whereby said control current reaches a maximum when the current through said resistor reaches -a minimum, electromagnetic means responsive to said last mentioned l eans, coupling means between said electromagnetic means and said variable reactance for varying said reactance under control of said electromagnetic means.
  • va switching arrangement for facilitating the Vpreliminary and final tuning of .
  • va switching arrangement for facilitating the Vpreliminary and final tuning of .
  • said relay circuit includes two rectifying devices connected in opposition :and a relay arranged between the anode of the iirst rectifying device and the cathode of the second rectifying device and shunted by a resistor.
  • said control amplifier includes two valve amplifying stages and an interstage network including therein a rectifying device, said coupling network comprising :a condenser connected to be charged through said rectifying device when the anode potential of the rst amplifying stage becomes increasingly posi- 1'1 tive, the rectier preventing 1the condenser from discharging when the said anode potential ⁇ decreases, whereby change of direction of said controlling current c auses said control amplifier to cease to yield an output.
  • said relay circuit includes two rectifying devices connected in opposition and a relay shunted by a resistor arranged between the positive terminal of the first rectifying device and the negative terminal of the second rectifying device.

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  • Measurement Of Resistance Or Impedance (AREA)
US509211A 1942-12-08 1943-11-06 Tuning arrangement for thermionic valve circuits Expired - Lifetime US2483409A (en)

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Application Number Priority Date Filing Date Title
GB17428/42A GB561977A (en) 1942-12-08 1942-12-08 Improvements in or relating to tuning arrangements for thermionic valve circuits

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US2483409A true US2483409A (en) 1949-10-04

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BE (1) BE467464A (is")
FR (1) FR934785A (is")
GB (1) GB561977A (is")

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2653243A (en) * 1948-08-17 1953-09-22 Westinghouse Electric Corp Automatic tuning of resonant circuits

Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1626724A (en) * 1923-12-31 1927-05-03 American Telephone & Telegraph Frequency-controlling system
US1645850A (en) * 1927-10-18 Regulator
US1907965A (en) * 1927-11-01 1933-05-09 Rca Corp Automatic tuning
GB441691A (en) * 1934-07-20 1936-01-20 Cole E K Ltd Improvements in or relating to the tuning of radio receivers
US2182377A (en) * 1937-05-01 1939-12-05 Radio Patents Corp Method and means for tuning electric oscillatory circuits
US2231996A (en) * 1936-03-26 1941-02-18 Radio Patents Corp Frequency variation response circuit
US2266065A (en) * 1936-07-01 1941-12-16 Muller Egon Nicolas Automatic tuning device for radio receivers
US2270917A (en) * 1939-02-08 1942-01-27 Rca Corp Electrical remote control system
US2358454A (en) * 1942-04-29 1944-09-19 Rca Corp Automatic circuit tuning
US2376667A (en) * 1943-03-29 1945-05-22 Rca Corp Automatic tuning of transmitters

Patent Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1645850A (en) * 1927-10-18 Regulator
US1626724A (en) * 1923-12-31 1927-05-03 American Telephone & Telegraph Frequency-controlling system
US1907965A (en) * 1927-11-01 1933-05-09 Rca Corp Automatic tuning
GB441691A (en) * 1934-07-20 1936-01-20 Cole E K Ltd Improvements in or relating to the tuning of radio receivers
US2231996A (en) * 1936-03-26 1941-02-18 Radio Patents Corp Frequency variation response circuit
US2266065A (en) * 1936-07-01 1941-12-16 Muller Egon Nicolas Automatic tuning device for radio receivers
US2182377A (en) * 1937-05-01 1939-12-05 Radio Patents Corp Method and means for tuning electric oscillatory circuits
US2270917A (en) * 1939-02-08 1942-01-27 Rca Corp Electrical remote control system
US2358454A (en) * 1942-04-29 1944-09-19 Rca Corp Automatic circuit tuning
US2376667A (en) * 1943-03-29 1945-05-22 Rca Corp Automatic tuning of transmitters

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2653243A (en) * 1948-08-17 1953-09-22 Westinghouse Electric Corp Automatic tuning of resonant circuits

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FR934785A (fr) 1948-06-01
BE467464A (is")
GB561977A (en) 1944-06-13

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