US2038359A - Control system - Google Patents

Description

Apnl 21, 1936.. AD. E. HARNETT CONTROL SYSTEM Filed Oct. 5, 1934 2 Sheets-Sheet 1 ES NN w Y SGS.

INVENTOR an/Z- ff/anne?? ATTORNEYS April 2l, `1936. D. E. HARNETT CONTROL SYSTEM Filed Oct. 5, 1934 2 Sheets-Sheet 2 ATTORNEYS Patented Apr. 2l, 1 936 PATENT oFFlcE coNrRoL SYSTEM Daniel E. Harriett, Tuckahoe, N. Y., assignor to Hazeltine Corporation, a corporation oi' Dela- Application October 5, 1934, Serial No. 747,044

9 Claims.

'I'his invention relates to the reception and selection of modulated carrier signals.

The principal objects ofthe invention are to improve the fidelity of reception of carrier wave signals and to control the signal selection and fidelity.

In my copending application, Serial No. 728,- 437, filed May, 31, 1934, there is described a radio receiver in which fidelity of reception is improved by employing a frequency selecting system by which the selected band of frequencies may be extended in one direction or the other. This has the effect of admitting a wider range of one of the side bands. The direction in which the selected band should ordinarily be extended is that opposite from which a strong interfering signal on a nearby channel may happen to be present.

In accordance with the present invention there is provided a control arrangement suitable for '30 Y operating the system disclosed in my said application Serial No. 728,437,

The control arrangement serves to tune ythe receiver to a desired signal and also to extend the selected band of frequencies. Preferably, a single control knob operates either the tuning mechanism or the band width adjusting mechanism, independently of each other, as desired.

A feature of the arrangement is the provision of a shaft (containing the control knob) which may be moved in both an endwise and a rotary direction. The tuning means and the band Width adjusting means are preferably both controlled by rotary motion of the shaft and knob, endwise motion being used to operatively engage the shaft with either the signal selector or the band width adjuster. y

Another feature of the arrangement is the provision of a camming means which operates the `band width adjusting means to the position of a relatively narrow, or minimum, band width when the knob, or shaft, is moved into the position for tuning.

Fig. 1 is the same as Fig. 1 of my copending application Serial No. 728,437, and shows a superheterodyne receiver having a circuit adapted to be controlled by the mechanical control arrangement of this invention;

Fig. 2 is the same as Fig. 2 of my said application, Serial No.`728,437, and shows graphically how the selected'band may be extended in accordance with this invention;

` Fig. 3 shows a mechanical control arrangement in accordance with the invention, associated with the chassis of a radio receiver;

Fig. 4 is a sectional view taken along the line 4-4 of Fig. 3; and

Fig. 5 is a view of a. detail, taken along line 5-5 of Fig. 1.

The receiver of Fig. 1 is of a conventional 'superheterodyne type comprising an antenna I0 (Cl. Z50-20) and ground II; a radio-frequency amplifier I 2 a modulator tube I3, an intermediate-frequency amplifier tube I4; a detector and audio-frequency amplifier I5; and a loudspeaker I E. The radio-frequency amplifier I2 and the detector and audiofrequency amplifier I5 are shown in generalized box form since their details are well understood in the art and constitute no part of this invention. The modulator tube I3 is coupled to the radio-frequency amplifier I2 by a. radio-frequency coupling system I'I tunable by a variable condenser I 8. There is provided a local oscillator indicated generally by the box I9 having an output circuit 20 tunable by a variable condenser 2I. The output of the oscillator is coupled to a coil 22 which is located in the grid-cathode circuit of the modulator tube I3.

In accordance with well-known modulator operation, modulation of the radio-frequency signals by the local oscillations occurs at the tube I3. There consequently appears at the output of the modulator the intermediate-carrier frequency which is the difference between the signal-carrier frequency and the local oscillator frequency. The intermediate-carrier frequency has associated therewith the usual two sidebands of modulation which extend six or more kilocycles on either side of the intermediate-carrier frequency. To maintainthe intermediate-carrier frequency substantially constant, the local oscillator frequency is varied by the condenser 2I by the same amount and in the same direction, that the resonant frequency of the radio-frequency selecting circuit is varied by the condenser I8. 'I'he two condensers I8 and 2| are ordinarily operated by a single mechanical control device indicated generally by the dotted lines U.

The intermediate-carrier frequency amplifier tube AI4 is coupled to the output of the modulator tube I3 by an intermediate-frequency selecting system 23 of the double-tuned type. This selecing system comprises a primary coil 24 electromagnetically coupled to a secondary coil 25. The primary coil 24 has shunted across it a fixed condenser 26 and a variable condenser 2I. The secondary coil 25 has shunted across it a. fixed condenser 28 and a variable condenser 29. The two variable'condensers 2l and 29 are operated simultaneously by a single mechanical control device indicated generally by U. The mechanical control device is arranged so that operation thereof varies the capacities of the two condensers 21 and 29 in the same direction.

Another intermediate-frequency selecting system 30 serves to couple the tube I4 to the detector and audio amplifier I5. This latter selecting system likewise comprises a. primary coil 3| coupled "to a secondary coil 32, these coils being tuned to the intermediate-carrier frequency by condensers 33 and 34, respectively. so that a relatively narrow band centered at the intermediate carrier frequency is selected. Coupling system 30, however, is not provided with variable condensers like condensers 21 and 29 of selecting system 23.

Referring to system 423, the primary and secondary circuits are each adjusted to tune to the intermediate-carrier frequency (frequently in the neighborhood of kilocycles) when the rnechanical control device U' is in an intermediate position between the minimum and maximum limits of its range of operation. Preferably, the mid-range position of the device is chosen as that in which the system is so tuned. This position of U', then, is the neutral, or normal positionin which the system is tuned to resonance at the intermediate-carrier frequency. In this neutral position the variable condensers 21 and 29 are adjusted to have capacity values intermediate their maximum and minimum values. These ca.- pacity values, in the neutral position, should preferably besuch that the resonant frequency can be shifted from the intermediate carrier frequency in both directions by an equal amount.

The condensers 21 and 29 are so .correlated by the device U that movement of U produces equal changes of the resonant frequencies of the primary and secondary circuits of the coupling system 23. Hence, these primary and secondary circuits are always tuned to the same frequency throughout the range of operation of device U. In the convenient case where coils 24 and 25 are equal and condensers 26 and 28 are equal, condensers 21 and 29 may also be equal and made to have their capacities varied equally by movement of device U'.

In the neutral or normal condition, the bandselecting characteristic of the' selecting system 23 is the same as that of the succeeding selecting system 30, and is represented graphically by curve A in Fig. 2, which is a graph of relative output voltage cn a logarithmic scale plotted against frequency on a linear scale. The intermediate carrier frequency is taken to be 175 kilocycles. Since the systems 23 and 30 both have the characteristic A, the overall characteristic Vof the two systems is as represented by curve B, which is the square of curve A.

An inspection of curve B indicates that when the condensers 21 and 29 are in the neutral position the system is highly selective. If the selected band width be taken as that at which the relative output voltage is half the peak voltage, the band Width passed is less than .4 kilocycles wide, that is, less than 2 kilocycles on each side of the carrier.

In accordance with the usual desired tuning operation the receiver is tuned with the main tuning control device U with the control device U' set in the most selective, or neutral, position. After the desired signal is accurately tuned in, the device U' is adjusted to expand the band Width the desired amount on the side away from the strongest interference.

When the control device U' is moved to decrease the capacity of condensers 21 and 29, the resonant frequency of the selecting system 23 is shifted upward with respect to the intermediatecarrier frequency. For an upward shift of 5 kilocycles in the resonant frequency of system 23 the characteristic shifts from that of curve A to that of curve C. The overall relative voltage output characteristic now takes the form of curve D which is the product of curves A and C. An inspection of curve D shows that the overall resonance peak has shifted about 21/2 kilocycles, and that the band width at which the output voltage is half the peak voltage has increased to about 6 kilocycles. l

It is significant to note that the greatest shift has occurred at the high-frequency side of curve D, the low-frequency side having shifted upward very little. Consequently, most of the increase in band width has taken place in the region of the upper sideband. Hence, a much wider range of the upper frequency sideband is selected under the condition of curve D than under the condition of curve A, the selected portion of this sideband having increased from less than 2 kilocycles to more than 5 kilocycles. This means that the audioffrequency range has been correspondingly increased.

The Width of one sideband, and hence the audio-frequency range, may be further extended by increasing the detuning of system 23 from the intermediate carrier frequency. Curve E shows the characteristic when the system 23 is detuned by l2 kilocycles .from the intermediate carrier frequency. The double peak effect is created by tuning system 23 beyond the frequency range within which the product of the two response curves A and C is a single peaked curve. greater output at the peak near 175 kilocycles, relative to the peak near kilocycles is due to the added selectivity of the radio frequency selecting system which is effective near frequencies corresponding to 175 kilocycles. plicity of explanation the effect of the radio frequency amplifier is not shown in curves A, B, C and D.

It may often be desirable to increase the number of intermediate frequency tuned circuits. 5h

This may be done by utilizing two intermediate frequency amplifier tubes in tandem with three double tuned coupling systems like systems 23 and 30, that is six intermediate frequency tuned circuits. may be designed like system 23 of Fig. 1 and a second of the systems may be designed to detune only one of the two tunedcircuits thereof.

In such a case, it will be convenient to use a three-gang midget condenser having two like sections for the doubly adjustable system and one smaller capacity section for the coupling system having only one adjustable circuit. ASuch an arrangement would have the advantage of tending to atten out the two peaks shown in curve E of Fig. 2, since the said smaller capacity section will not shift the resonance of its tuned circuit as far as the resonance of the doubly adjustable circuits are shifted. Hence the circuit of the said smaller capacity section will be resonant between these two peaks.

As an alternative arrangement, it would be possible to use like condenser sections but different inductance values. For example, the doubly adjustable system such as 23 could be constructed to have equal inductances, whereas the second coupling system having only one of the tuned circuits adjustable could have the inductance of the adjustable circuit somewhat smaller than the other inductance of the same system.l

A similar eifect may be obtained by using six tuned circuits as before, but only one intermediate frequency amplifier tube. In such a case three tuned circuits may be used in each of the coupling systems corresponding to systems 23 and 39 of Fig. 1; or if desired, four tuned circuits might be used in one of the coupling systems and two tuned circuits in the other.

Regardless of what particular arrangement of tuned circuits is used it is highly desirable that For the simff- In the latter case, one of the systems at least three, and preferably four or more, tuned circuits be arranged in tandem in the intermediate frequency amplifier, in any manner familiar to those skilled in the art.k It may be stated as a general proposition that some. normally from one-third to three-fourths of the total number of tuned circuits, should be shifted in frequency by the device U'.-

From the foregoing it is seen that it is not essential that all of the adjustable circuits (or any two of them, for that matter) have equal rates of resonance shift. All that is required is that the resultant shift be suilicient for the'purpose herein set forth.

In a manner analogous to that described above, the lower sideband, instead of the upper sideband, could be extended, by moving the mechanical control device U in theopposite direction.

The particular `sideband which is chosen for expansion should ordinarily be that which is most free from interfering signals. For example, if a strong interfering signal is present in the vicinity of the upper sideband, the lower sideband should be chosen for expansion.

Owing to the fact that the voltage output changes with the manipulation of device U' (e. g., curves B and D of Fig. 2), a system of automatic volume control should be employed if it is desired toproduce a more uniform output. Any conventional automatic volume control system may be employed, such as that shown in H. A. Wheeler Patent 1,879,863. The automatic volume control voltage should be derived from a point in the system subsequent to the intermediate-frequency amplifier system.

The sources of direct voltage for placing the tube electrodes in an operative condition are not shown in detail, but are simply represented as B, C and Screen to indicate, respectively, the anode, the grid biasing and screen voltages, No source of cathode-heating current is indicated, since any well-known method of cathodeheating may be employed.

Figs. 3, 4 and 5 show a mechanical arrangement for tuning and for displacing and extending the sideband in the manner described above. Fig. 3 is a side view taken through a'section of a radio chassis, and Fig. 4 is a section taken along the line 4-4 of Fig. 3. The mechanical arrangement comprises a chassis pan 40 having a front vertical portion 4|. A shaft 42 extends underneath the chasis pan and through the front portion 4 I, through the brackets 43 and 44, the double brackets 45 and 46 and the single bracket 41. A knob 48 is attached tothe end of the shaft 42 at the front of the chassis.

There is set between the brackets 43 and 44, a pinion 49 provided with sleeves 56 and 5| which fit through the bearing holes of brackets 43 and 44. A pulley 52 is set within the double brackets 45 and 46 and proyided with sleeves 53 and 54 which't within the bearing holes of the bracket. Sleeves 5| and 53 are provided with teeth at their outer peripheries for the purpose of engaging with a pin 55 fastened through the shaft 42. The shaft 42 may be rotated and mayalso be moved endwise through the sleeves of pinion 49 and pulley 52 to the extent permit-ted by movement of the pin 55 between the sleeves 5| and 53.

A pulley cord 56 mechanically connectsl the pulley 52 with a pulley 51 of a condenser shaft 58. The shaft 58 has attached thereto the tuning condensers of the radio frequency amplifier and the local oscillator circuits, including condensers |8 and 2|. These tuning condensers,

which are located in the condenser housing 8|, are not shown in detail since their mechanical construction constitutes no part of the invention.

'I'he pinion 49 is meshed with a pinion 59 fastened to a shaft 60, the pinion 59 being located between the brackets 43 and 44. There is attached to the inner end of the shaft 60 a bevel gear 6| which engages with a corresponding bevel gear 62 fastened to a shaft 63. The shaft 63 has attached thereto the adjustable condensers 21 and 29 (not shown in Figs. 3 and 4), and also all other similar adjustable condensers used in the receiver.

A stud 64 is rmly fastened to the front portion 4| of the chassis by means of' locking nuts 65 and 66. There is placed on the stud 64 a sleeve 61 which is adapted to lslide endwise along the stud. Rotary movement of the sleeve 61 is prevented because of the presence of a ball 68 in a ball recess 69 provided in the sleeve and a corrtesonding spline 10 provided in the top of the s u 'I 'here is fastened to shaft 42 a collar 1| provided with a flange 12 which engages in an annular groove 13 of the sleeve 61. The lower portion of the sleeve 61 is provided with a camming frameA composed of two rods 14 and 15 bent into the form shown, so that they slant downwardly and outwardly from each other when viewed from the front of the chassis. The construction of this camming frame is more clearly shown in Fig. 5, which is a section taken along 15, for a purpose which will be disclosed hereinafter.

'I'he shaft 42 has two operating positions: (1) that in which the shaft is pushed all the way inward so that pin 55 meshes with the teeth of sleeve 53; and (2) that in which the shaft is pulled all the way outward so that pin 55 meshes with the teeth of sleeve 5|. This arrangement of pin 55 and sleeves-5| and 53, then, constitutes a clutch such that rotation of knob 48 can be made to rotate either the pulley 52 and the tuning condensers, or else the pinion 49 andthe band width adjusting condensers on shaft 63.

The function of the-cam, or camming frame, attached to sleeve 61, is as follows: It is observed that when the shaft 42 is placed'so that pin 55 is in an endwise position intermediate the' two sleeves 5| and 53, as shown, the pin 16 'protruding from shaft 60 is also in an intermediate position with respect to the extremities of the rods 14 and 15 of the camming frame. When the shaft 42 is pushed endwise a distance o: so that pin 55 engages with the teeth of sleeve 53, the sleeve 61 is likewise moved the same distance :z: in the same direction so that the pin 16 becomes located between the closely adjacent anterior portions 11 and 18 of the rods 14 and 15. Hence, in this position of the cam, shaft 60 can only be in one position:-that in which the pin 16 is vertical. In this position of the shaft 60, the adjustable condensers on shaft 63 are adjusted to provide the minimum band width.

When, on the other hand, the shaft 42 is pulled outwardly from the aforementioned intermediate position, the shaft moves a distance y until pin 55 engages with the teeth of sleeve 5|. The sleeve 61 likewise moves the same distance y in the same direction so that pin 16 now lies between the widely separated posterior portions 19 `and 80 of rods 14 and 15, respectively. In this position, then, the shaft 68 is free to rotate about 'line5--5 of Fig. 3. A pin 16 is set within the top of shaft 60 between these two rods 14 and 180 between the limits permitted by the striking of pin 18 on the portions 19 and 80 of rods 1l and 15. This 180 rotation is sufficient to permit the desired degree of band expansion. But when knob 4B is pushed inwardly again toward the tuning position, pin 16, if not already in the vertical position of minimum band width, strikes either rod 14 or 15 and is thereby cammed until it does reach the vertical position between the portions 11 and 18.

By this means, it is assured that the tuning operation is always performed under the condition of minimum, or a relatively narrow, band width. This is the condition under which tuning can be performed with the greatest facility and precision, for the least interference is incurred.

I claim:

1. In a radio receiver having a signal selector and a band width adjusting arrangement, a mechanical tuning and band width control mechanism comprising a pair of axially aligned rotary sleeves having engaging teeth, one of said sleeves being operably connected with a signal tuning device and the other of said sleeves being operably connected with a band width adjusting device, a shaft, positioned through the axis of said sleeves, having endwise and rotary movement relative to said sleeves, means attached to said shaft for engaging with the teeth of either of said sleeves, whereby when said shaft is moved endwise in one direction said means engages with the teeth of one of said sleeves, and when moved endwise in the other direction said means engages with the teeth of the other of said sleeves and means operably connecting said shaft with the sleeve of said band width adjusting device for automatically operating the latter to a position of minimum band width when said shaft is axially moved to effect engagement of the other of said sleeves and said engaging means.

2. In a radio receiver having a signal selector and a band width determining arrangement, a mechanical tuning. and band Width control mechanism comprising a shaft having endwise and rotary movement, means for tuning to a signal by rotary movement, in one endwise position, and means for controlling the band width by rotary movement in a second endwise position, a camming device interconnecting said shaft and said band width controlling means which automatically operates said latter means to a position of minimum band Width when said shaft is moved to said first endwise position.

3. In a radio receiver having a signal selector and a band width determining arangement, a mechanical system for controlling all the selective properties of the receiver by a single knob, which comprises means permitting rotational and endi Wise motion of the knob, means for tuning the signal selector by rotational motion in a first endwise position of said knob, means for moving said knob endwise to a second position, means for independently varying the band Width by rotational motion in said second-endwise position, and means for operating said band width determining arrangement to a relatively narrow band Width when said knob is moved to said first endwise position.

4. Mechanism according to claim 3 in which said means for operating said band width determining arrangement to a relatively narrow band idth comprises a cam operated by said knob, said cam having a surface which moves said band width varying means to provide said narrow band width when said knob is moved to said rst endwise position.

5. Mechanism according to claim- 3 in which said means for operating said band width determining arrangement to a relatively narrow band width comprises a member placed on a shaft and slidable endwise on said shaft in response to said knob, said camengaging with a corresponding member on a shaft operably connected with said band width varying means.

6. In a radio receiver having a signal tuning device and an adjustable band width determining device, rotary mechanical means for adjusting said tuning device, rotary mechanical means for adjusting said band width determining device, a shaft having rotary and endwise paths of motion for operating each of said devices, by rotary motion, independently of the other, said shaft being provided with an engaging means which in a iirst endwise position of said shaft engages said tuning adjusting means, and in a second endwise position of said shaft engages said band width adjusting means, and camming means for operating said band width adjusting means to a position which produces a relatively narrow band width when said shaft is moved to said first endwise position.

7. In a radio receiver having a signal selector and a band width adjusting arrangement, a mechanical control system for operating said signal selector, andsaid band width adjusting arrangement, comprising a first toothed rotary member operably connected with said signal selector, and a second toothed rotary member operably connected with said band width adjusting arrangement, a first shaft extending axially through said toothed members and adapted to have .axial and rotary' movement with respect thereto, a pin fixed to said shaft and adapted to engage by endwise movement of said shaft with the teeth of either of said members, and means for operating said band width adjusting arrangement to a position of minimum band Width when said shaft is moved axially to engage said pin with said first toothed member, said means comprising a second rotary shaft operably connected with said band width adjusting arrangement and a camming device connected with said first shaft which engages with a member attached to said second shaft to rotate said second shaft to the position of minimum band width.

8. In a modulated carrier receiver, a band pass selector, tuning means for tuning the receiver over a range of frequencies, band control means for independently adjusting the selected band Width, and camming means for automatically operating said band control means to the position of substantially minimum band Width when the receiver is being tuned.

9. In a superheterodyne receiver, a frequency changer, a single knob for controling all the selective properties of the receiver, tuning control ineans for tuning the frequency changer by rotation of the knob in a first axial position, band width control means for independently adjusting the band width of the selector by rotation of the knob in a second axial position, and a camming means for operating the selector to the position of substantially minimum band width when said knob is moved from the second to the first axial positions.

DANIEL E. HARNETT.

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