US3878466A

US3878466A - Varactor tuning system

Info

Publication number: US3878466A
Application number: US331921A
Authority: US
Inventors: Melvin C Henrickson
Original assignee: Zenith Radio Corp
Current assignee: Zenith Electronics LLC
Priority date: 1973-02-12
Filing date: 1973-02-12
Publication date: 1975-04-15
Anticipated expiration: 1992-04-15

Abstract

A television channel selector includes UHF and VHF tuners each having a varactor as the frequency-determining element. A number of fixed contacts on a rotary switch are respectively associated with different channels in both the VHF and UHF regions of the spectrum; also included on the switch are a pair of selection contacts. Printed on the same substrate which carries the switch contacts are a plurality of resistors which together constitute a voltage divider that has individually different junctions between the resistors connected to respective different ones of the fixed contacts. A fast-tuning shaft drives the selection contacts over the fixed contacts. That shaft is detented each time the selection contacts are moved over a chosen number of the fixed contacts. A slow-tuning shaft is coupled through a gear system to the fast-tuning shaft. The slow-tuning shaft is detented in rotational increments that correspond to movement of the selection contacts, through the gear system and the first shaft, from each one of the fixed contacts to the next. The selection contacts read out a voltage from the divider which is fed to the varactors in determination of frequency. For fine tuning, the varactor control voltage is derived from a tap on a potentiometer the opposite ends of which are connected by the selection contacts across selected individual different ones of the resistors in the voltage divider.

Description

United States Patent Henrickson Apr. 15, 1975 VARACTOR TUNING SYSTEM tuners each having a varactor as the fre uenc s q y [75] Inventor: Melvin C. Henrickson, Elmhurst, Ill. determming element A {lumber of ,flxcd on a rotary switch are respectively associated with different [73] Asslgneei Zenith a o Corp r i n, C g channels in both the VHF and UHF regions of the 111. spectrum; also included on the switch are a pair of se- [22] Filed Feb 12 1973 lection contacts. Printed on the same substrate which carries the switch contacts are a plurality of resistors [21] Appl. No.: 331,921 which together constitute a voltage divider that has individually different junctions between the resistors 52 us. Cl. 325/464; 338/120; 334/15 coimected respective differemPnes the f 51 Int. Cl. H03j /02 A fastmnmg shaft ("was 56mm" [58] Field of Search u 325/464, 465; 334/14 contacts over the fixed contacts. That shaft 15 detented 323/79 338/92 95 118 120 172 each time the selection contacts are moved over a chosen number of the fixed contacts. A slow-tuning shaft is coupled through a gear system to the fastiiillifififfiiiinlfifsiiitiisiiifpilfiiif2.252211%; UNITED STATES PATENTS selection contacts, through the gear system and the Bourns fir t shaft from each one of the fixed contacts to the 3308311 11/1961 Juhe 338/202 next. The selection contacts read out a voltage from the divider which is fed to the varactors in determina- Primary Examiner-Benedict V. Safourek Attorney, Agent, or FirmNicholas A. Camastro tion of frequency. For fine tuning, the varactor control voltage is derived from a tap on a potentiometer the opposite ends of which are connected by the selection contacts across selected individual different ones of the resistors in the voltage divider.

3 Claims, 9 Drawing Figures fii F F839 58 78 Channel I Selector I L\ AFC.

4 Circuit FATENTEBAPR 1 5:95

SHEET 1 BF 4 (552mm ccUc Fi gmmPmsiss 3,878,466

SUEETEUF Q 1 1 8+ I 104 1 1 FIG.2 100 17 16 105 l 9 Channel 8 118 Selector v 121 a 6 5 12o 5 E P, "\TENTF.UAPR 1 5191s FIG.3

A+ 21 Reg.B+ 163183 182 UHF 161 Tuner 1 24 SWi'lZCh 1601 1 f""l (10C! 1 F20 Resistor Network 171 179 152 F 166 VHF 156 Tuner A' 1 T 186 174 Control Network FIG 4 151 FATENTEDAPR l SISYS FIG. 5c

FIG. 5d

FIG.5e

VARACTOR TUNING SYSTEM BACKGROUND OF THE INVENTION The present invention relates to television channel selectors. More particularly. it pertains to electrical circuitry and mechanical apparatus capable of selecting channels in both the UHF and VHF regions of the television spectrum.

A typical television tuner or channel selector includes a radio frequency amplifier. a local oscillator and a mixer for heterodyning the received radio frequency signal with the local oscillator signal to develop a fixed intermediate frequency signal which then is processed to yield the necessary image and sound reproduction information. With this approach. it is necessary that both the radio frequency amplifier and the local oscillator be tunable over a range of frequencies in order to be able to receive all of the different television channels. With the expansion of commercial television broadcasting from the very high frequncy (VHF) spectrum intro the ultra-high frequency (UHF) spectrum. the required tuning range was greatly increased. Tuning usually has been accomplished by using two separate tuners. one for channels inthe VHF spectrum and the other for channels in UHF spectrum. In most instances. each tuner has been provided with its own knob or dial for manipulation by the user. Thus. the VHF knob enables selection from among VHF channels 2-13. while the UHF knob is employed to select from among UHF channels 14-83. Because of the substantially larger number of UHF channels. however. the ease or accuracy of selection ofa particular UHF channel often is inferior as compared with selection ofa particular VHF channel.

OBJECTS OF THE INVENTION It is. accordingly. a general object of the present invention to provide a television channel selectro which features improved ease and assuracy of use in selecting particular different channels.

Another object of the present invention is to provide a combined UHF and VHF channel selecting system in which access to different adjacent ones of both the UHF and VHF channels is achieved by manipulation of the same tuning knob.

A further object of the present invention is to provide a television channel selector which takes advantage of the attributes of printed circuitry in achieving switch selection between different channels.

Still another object of the present invention is to provide a television channel selector which includes a single fine tuning control for all'channels in both the VHF and UHF spectra.

SUMMARY OF THE INVENTION A combined UHF and VHF television channel selector constructed in accordance with the present invention includes tuning means having at least one varactor as the frequency determining elment with the frequency determined being a function of the voltage presented to a terminal of the varactor. A rotary switch features a predetermined number of fixed contacts respectively associated with different channels in both the VHF and UHF spectrum together with at least one selction contact that is movable over respective different ones of the fixed contacts. A plurality of resistors are series connectedto form a voltage divider. and individually progressive different junctions between the resistors are connected with respective different ones of the fixed contacts. For fast-tuning. a first rotatable shaft is coupled to the selection contact in order to drive the same successively over the fixed contacts. The first shaft is detented each time upon movement of the selection contact successively over a chosen number of the fixed contacts. a slow-tuning means includes a second shaft which is mechanically coupled to the first shaft by agear system. The second shaft also is detented. but in rotational increments corresponding to movement of the selection contact. through the gear system and the first shaft. from each one of the fixed contacts to the next. Finally. the arrangement includes means for coupling the selection contact to the varactor terminal in order to control the frequency determining voltage. Also featured is a fine tuning means which includes a potentiometer that has a movable tap coupled to the varactor terminal in order to supply the frequency determining voltage. The channel selection means includes a coupling of the opposing ends of the potentiometer selectively across different individual ones of the resistors in order to adjust the level of the frequency determining voltage in correspondence with changes in channels.

BRIEF DESCRIPTION OF THE DRAWINGS The features of this invention which are believed to be novel are set forth with particularlity in the appended claims. The invention. together with further objects and advantages thereof. may best be understood. however. by reference to the following description taken in conjunction with the accompanying drawings. in the several Figures of which like reference numerals identify like elements. and in which:

FIG. I is a schematic diagram of a combined UHF and VHF television channel selector;

FIG. 2 is a schematic diagram ofa switching arrangement used in the tuner of FIG. 1;

FIG. 3 is a diagrammatic plan view of a rotary-switch contact arrangement which incorporates the circuitry shown in FIG. 2;

FIG. 4 is a schematic diagram which includes a mechanical drive system for tuning the selector of FIG. 1;

FIG. 5a is a side elevational view of an alternative mechanical driving arrangement;

FIG. 5b is a front elevational view of an indicator dial utilized in the arrangement of FIG. 511;

FIG. 50 is afragmentary cross sectional view of a portion of the arrangement of FIG. 5a;

FIG. 54 is a fragmentary view of a portion of the apparatus in FIG. Scas taken along the line 5d-5d in that FIG.; and

FIG. Se is another fragmentary cross sectional view of a portion of the apparatus shown in FIG. 5c.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT As illutrated in Flg. l, a television channel selector includes a VHF tuner 20 and a UHF tuner 21. The primary frequency determining element in each of

tuners

20 and 21 are

respective varactors

22 and 24. Having already found commercial utilization. varactor tuned television channel selectors are in themselves well known. It will. therefore, suffice for present purposes to note that each varactor exhibits a change in capacitance in response to variations in a potential presented across its two terminals. Since the capacitance of the varactor is combined with a fixed inductance to constitute a tuning circuit the point of resonance of which establishes the operating frequency of the associated circuitry. variation in the value of the cpacitance serves to tune that circuitry to different frequencies. In this instance, one terminal of each of

varactors

22 and 24 is connected to ground as indicated, so that it is a voltage presented to the other terminal of each varactor which determines the frequency of operation. In the specific case of

tuners

20 and 21, the function controlled by the respective varactors is the local oscillator frequency of the superheterodyne type tuning arrangement. Of course, the output of each tuner is a fixed intermediate frequency television signal which then is amplified in a portion of the remainder of the television receiver and processed to develop the image and sound reproduction information employed to produce the television picture and audio accompaniment.

In the United States and Canada. the governments have allocated different ranges or bands in the frequency spectrum for television usage. A first band extends from 54 and 72 megahertz and is further divided into successive individual channels each having a width of 6 megahertz. This band accommodates channels 2 through 4. The second band embraces 76 to 88 megahertz. accommodating channels and 6. Assigned the range of l74 to 216 megahertz is a third band which similarly accommodates channels 7 through 13. All three of the aforementioned bands are denominatedas being in the very high frequency or VHF portion of the spectrum. Finally. a fourth band has beenassigned in what is termed the utlra high frequency or UHF portion of the spectrum. This band extends from 570 to 890 megahertz and is subdivided into channels 14 to 83.

Because of the wide separation in frequency as between the first and second bands, on the one hand, and the third band on the other, it has been customary in the design of many VHF tuners to provide a band switch to make a coarse adjustment in its operating frequency when switching between

channels

6 and 7. Thus. tuner is associated with a first switch 26 which is operated by suitable cams on a channel selector 27 to connect a source of potential B+ along one path to tuner 20 during the selection of any of channels 2 through 6. On the other hand, selector 27 closes a switch 28 to connect source B+ as an energizing potential to tuner 20 over another path when selecting any 'of'channels 2 through 13. A bias potential from a source C- is connected to tuner 20 in the first mentioned path through a resistor 29. When switch 26 is closed. the B+ potential as applied to the tuner is effectively reduced in value by the C- potential and thereby impresses a comparatively low positive voltage on tuner 20 to maintain operation of the tuner in one of channels 2-6.

Connected to the junction between switch 28 and tuner 20 is the emitter of a transistor 30, the collector of which is returned to ground through a resistor 31. A bias resistor 32 is connected between the collector and base of transistor 30. The potential appearing across resistor 31 is fed from the collector of transistor 30 to the base of a second transistor 34 which has its emitter connected to the B+ potential source. Its collector is connected into tuner 21 in order to provide its primary operating potential. When switch 28 is closed, a positive potential appears at the emitter of transistor 30 as a result of which the voltage at theh top of resistor 31 is sufficient to cut off operation of transistor 34 and UHF tuner 21 is thereby disabled. On the other hand, when switch 28 is open so as to disable VHF tunber 20, transistor 34 is in an on condition and thereby connects the B+ energizing potential to tuner 21.

Control voltage is supplied to varactor 22 over a lead 36, while a lead 38 conveys control voltage to varactor 24. Leads 36 and 38 are shunted to ground by

respective filter capacitors

40 and 42. Moreover, lead 36 connects to one corner 43 of a bridge 44, and lead 38 connects to a diagonally opposite corner 45 of the bridge. The bridge itself is composed of

resistors

46, 47, 48 and 49 which constitute its four different arms, respectively. Another corner 50 of bridge 44 is connected to a tap 52 on a potentiometer 53. The opposite ends of potentiometer 53 are connected to

respective switch contacts

54 and 55. Spaced alongside contact 54 are a succession of

separate switch contacts

58, 59, and 61. On the other hand. spaced alongside contact 55 is another series of

contacts

63, 64, 65, 66 and 67. Associated with contacts 63-67 is a voltage divider composed of a plurality of

resistors

71, 72, 73, 74 and connected in series between ground and a source of regulated B+ potential. Contacts 63-67 are individually connected to respective different junctions between successive ones of resistor 71-75. Also, contacts 58-61 are individually stagger-connected to respective different ones of contacts 6467 That is, contact 58 is connected to contact 64, contact 59 is connected to contact 65, and contact 61 is connected to contact 67. The dashed lines joining contacts 60 and 66, like the dashes lines in the center portion of voltage divider 70, serve to indicate the existence of additional and similarly-arranged contact pairs and voltage divider resistors. Finally. a pair of

movable switch contacts

78 and 79 serve individually to connect

respective contacts

54 and 55 to selected corresponding different ones of contacts 58-61 and 63-67. The movement of

contacts

78 and 79 is effected by channel selector 27.

The staggered interconnections and the physical orientation is such that at any one position

movable contacts

78 and 79 serve to connect the opposite ends of potentiometer 53 across a aprticular one of resistors 71-75. Thus, as

movable contacts

78 and 79 connect to fixed contacts on the voltage divider further from ground, the voltage range across potentionmeter 53 becomes correspondingly higher. Consequently, the voltage presented to bridge 44 from potentiometer tap 52 is increased whereupon the voltage presented to

varactors

22 and 24 similarly is increased. At the same time. and for any particular setting of

movable contacts

78 and 79, adjustment of the position of tap 52 on potentiometer 53 serves as a finer adjustment of the voltage level ultimately presented to

varactors

22 and 24. Thus, by suitable proportioning of the values of resistors 71-75 in the voltage divider,

movable contacts

78 and 79 serve to successively select a plurality of different channel-representative potentials. while potentiometer 52 serves during selection of any one particular channel as a fine tuning control.

Connected to the final corner 80 of bridge 44 is a potential derived from an automatic frequency control (AFC) circuit 81 and supplied through a balanced network 82. More particularly, network 82 includes a pair of

transistors

83 and 84 with the collector of transistor 83 connected to the B+ source through a resistor 85.

The collector of transistor 84 is connected through a diode 87 to a low voltage alternating current source A and also is shuted to ground by filter capacitor 88. The automatic frequency control signal from circuit 81 is fed through a resistor in common to the bases of both

transistors

83 and 84. A filter capacitor 91 couples the terminal output of circuit 81 to ground. Connecting the emitters of

transistors

83 and 84 are a pair of series connected

resistors

92 and 93. with the junction between those two resistors being directly connected to corner 80 of bridge 44.

In the conventional manner. AFC circuit 81 responds to frequency departures in the received signal. typically by detecting a portion of the intermediate frequency signal in the television receiver. and develops a control voltage which is applied. in this case through bridge 44. to

varactors

22 and 24 in order to compensate or neutralize that change in frequency.

A preferred arrangement of voltage divider 70 and its associated contacts and other connections is depicted in FIG. 2. A plurality of fixed contacts are spaced one after another in a column and are arranged to permit selection of any of channels 2 through 83. As shown. each individual contact is numbered with the channel or channels with which it is associated. The two contacts at either end. respectively. are associated with but a single channel and hence bear the

numbers

2 and 82. resepctively. All of the remaining contacts are each associated with two different adjacent channels; thus. the second contact from the bottom is denominated as being associated with both

channels

3 and 2. Moreover. it will be noted that each contact is associated with the same channel as is an immediately adjacent contact. Thus. the second and third contacts from the bottom are both associated with channel 3. In addition. the contacts respectfully associated with channels 4-5. 6-7 and 13-14 are split into two electrically siolated segments or sections. Of course. the dashed lines joining the contact associated with channels 16-17 and the contact associated with channels 82-83 indicate for drawing convenience the inclusion of a plurality of additional contacts spaced successively in that region and respectively associated with channels- I? to 82.

In the arrangement of FIG. 2. voltage divider 70 is divided into two portions. A first portion extends between a source of potential 8+ and ground and includes. in successive series combination. resistors 102-109. The associated contacts. for channels 14-83. are individually connected to respective different junctions between successive different ones of those resistors. The secondn portion of divider 70 is composed. again insuccessive series combination. of a plurality of resistors 112-117 with that combination of resistors again extending between a source of potential B+ and ground. It will be notedthat resister bridges the split contact associated with

channels

6 and 7. while resistor 123 similarly bridges the split contact associted with

channels

4 and 5. The reason those contacts are split and the additional bridging resistances are included is the need for anextra voltage increment between

channels

4 and 5 and between

channels

6 and 7 to accommodate the extra frequency difference that exists between those two pairs of channels. This is the same frequency difference mentioned above as occuring between the first and second and the second and third bandsof the frequency spectrum assigned to television usage. The use of the two separate voltage divider portions accommodates the similarly abrupt step in frequency that occurs in going from channel 13 to channel 14 which corresponds to changing from the third band to the fourth band mentioned above.

For selection of any particular channel. the opposite ends of potentiometer 52 are respectively connected to two different contacts which in this case are adjacent and which serve. as in the case of divider 70 in FIG. 1. to cause potentiometer 52 to be connected across an individual dividing resistor in the voltage divider. Thus. movable tap 52 on potentiometer 53 again serves as a fine tuning control. and the output from that tap is shown in this case as being connected to one terminal of var-actor 20 so as to present the frequency determining voltage to that element of the associated tuner. As before. channel selector 27 serves to drive the movable contacts associated with potentiometer 53 from one channel selecting position to the next.

In practice. the channel selection contacts may be laid out on a substrate more or less exactly as actually shown in FIG. 2 and the different associated resistors may then be printed alongside the contacts on the same substrate. Channel selector 27 then takes a suitable form for driving the movable contacts linearly along the array of fixed contacts. In order to achieve a more compact assembly. however. it is preferred to arrange the fixed contacts into a circle and use a rotary switch mechanism to drive the movable contacts. This is illustrated in FIG. 3 wherein a plurality of channel positions appear as segments of an annulus numbered successively 2-83. Although not detailed in FIG. 3 for convenience of drawing. the individual fixed contact structure at each channel position is like that shown in FIG. 2. That is. there is only a single contact segment at each of

channels

2 and 83 and the fixed contacts at the locations corresponding to channels 5. 7 and 14 are divided into two segments.

The different fixed contacts preferably are printed upon a ceramic substrate which need be only about two inches square. Each contact area or channel position may be assigned an arc of about 4.28 for accommodating all 82 channels while permitting space between the

channel

2 and 83 positions for connecting conductors. The connecting conductors each may be about 20 mils in width and spaced by the same amount which dimensions are well within present day printed circuit capabilities. Also. all of the different resistors shown in FIG. 2 may in practice be printed on substrate 130. generally adjacent to the respective different fixed contacts. a representative number of these printed resistors are actually shown in FIG. 3. Thus. resistor 106 bridges theh contacts associated with channel positions 16 and 17, while resistor 107 similarly bridges the positions corresponding to

channels

15 and 16. Resistor 108 bridges the fixed contact positions corresponding to

channels

14 and 15, while resistor 109 extends from the one channel 14 contact segment to an external connecting terminal 132 which in use. as indicated in FIG. 2, is to be connected to ground. Analogously. the one fixed contact segment associated with channel 13 is connected through a printed resistor 112 to an external terminal 134 which. again as indicated in FIG. 2, is to be connected to B+. Similarly. the fixed contact for channel 83 is connected through resistor 102 also to a B+ terminal 136. Step up

resistors

120 and 123 bridge the separated contacts associated in moving

betweeen channels

6 and 7 and

channels

4 and 5. respectively. Finally. an external terminal 138 is connected by a printed conductor to a central. circular conductive area 140. while another external terminal 142 is connected to an annular conductive area 144 spaced around area 140. These last mentioned conductive areas serve conveniently in practice to make contact with movable wiping contacts that are driven by the channel selecting mechanism so as also to wipe across the series of channel selection fixed contacts and thereby complete selective connection to the latter. An example ofthis kind of wiping contact arrangement will be shown in more detail in connection with FIG. a.

One form of channel selector mechanism is illustrated in FIG. 4. Also included in that Figure is a switch and resistor network which. while shown in block diagram form. is in this instance constructed in the manner described in FIG. 3 so as to be selective as a rotary switch. The frequency determining voltage from network 150 is fed to

varactors

22 and 24 of respective VHF tuner 20 and UHF tuner 21. At least basically, the electronic circuitry in H6. 4 is the same as that shown in FIG. 1; in FIG. 4. however. the different control stages are lumped on one block and denominated simply as a control network 151. Network 151 supplies B+ to

tuners

20 and 21 over

respective leads

152 and 153. while feeding automatic-frequency control potentials to the respective tuners over

leads

155 and 156. Also. in the manner of switches 126 and 128 of FIG. 1. network 151 is shown as including a band switch control lead 158 leading to tuner 20.

A fast-tuning means includes a first rotatable shaft 160 which may be turned by grasping a tuning knob 161. Shaft 160 is coupled to the movable selection contacts in the switch part of network 150 so as to drive those contacts from each one of the fixed contacts to the next. However. a first ball-detent 163 acts upon shaft 160 by means of flange 164 which is rigidly affixed to shaft 160 and includes the detent seat. The detent acts to resist movement of shaft 160 each time upon movement by the shaft of the switch selection contact successively over a chosen number of fixed contacts.

What may be termed a slow-tuning knob 166 is secured on an end of a second rotatable shaft 167. Mating spur gears 168 and 169 serve to couple shaft 167 to shaft 160 by way of a flange ring 170 carried upon shaft 160 by a bearing 171 and. in turn. coupled to flange 164 by means of the assembly including balldetent 163. Another ball-detent 173. carried between a rigid support 174 and a collar 175 affixed to shaft 167, serves to detent shaft 167 in rotatinal increments that correspond to movement of the selection contact in network 150, through gears 168 and 169 and shaft 160. from each one of the fixed contacts to the next in the switch portion of network 150.

In designing and assembling the actual mechanical structure. each of detents 163 and 173 is caused to be reasonably stiff so that. for example, when knob 161 is turned to rotate shaft 160, detent 163 yields but detent 173 does not yield and shaft 167 and its knob 166 remain stationary. On the other hand. upon rotation of knob 166, overcoming the detenting force of detent 173, that rotation is translated through the gear system. detent 163 and flange 164 to cause shaft 160 to rotate; in that case. then, it is detent 163 which does not yield as detent 173 is forced to yield. Of course. it is the presence of the gear system between the two shafts which permits such differential detent action.

In operation. knob 166 may be thought of as the VHF tuning knob. while at the same it also functions as a UHF slow-tuning knob. On the other hand. knob 161 serves as the UHF fast-tuning knob. That is. knob 166 may be turned one channel at a time so as to tune through thhe VHF range of channels 2 through 13 or thorugh the UHF range channel-by-channel. On the other hand. the turning of knob 161 from any one detent position on shaft 160 to the next causes an abrupt tuning change past a group of successive channels. On reaching the end of that group. the user may then again use knob 166 to move one channel at a time either upwardly or downwardly in the scale.

In one attractive arrangement. detent 173 has 12 de tent positions or points for each full rotation of shaft 167. corresponding to the 12 VHF channels. At the same time. the ratio between gears 169 and 168 is seven to one and detent 163 is selected to have seven detent points for rotatin of shaft 160. Consequently. knob 161 becomes a fast-tuning knob detented every 12 channels. When knob 166 is turned, starting at channel 2. the VHF channels are tuned in ascending order until 13 is reached. lF knob 161 is then advanced. the tuning jumps 12 channels. first to channel 26, then to channels 38. 50.62 and 74. and finally back to VHF channel 2 again. When the user desires to go from. say. channel 14 to channel 20, VHF knob 166 may be rotated by in order to cover the six channels involved. Alternatively. channel 20 also could be tuned by using UHF knob 161 and turning it one detent so as to jump from channel 14 to channel 26 after which VHF knob 166 would then be used to turn back-- wardly six individual channels.

In use. it is apparent that the successive UHF channel numbers may conveniently be distributed around the periphery of knob 161. while the VHF channel numbers are similarly distributed around the periphery of knob 166. By making those peripheries transparent or switch that includes a movable armature 182 connected to an A+ potential source for energizing the lamps. Armature 182 is moved by a suitable cam. indicated by dashed line 183, carried by flange 164 so as to effect energization of lamp 178 whenever shaft 160 is in the portion of its rotation corresponding to UHF switch contact selection. On the other hand. lamp 179 is energized during the other portion of the rotation of shaft 160 when VHF switch contacts 180 and 181 also are connected through

leads

185 and 186, respectively,

to control network 151 so as to provide the necessary band switching information for selectively activating the requisite one of

tuners

20 and 21.

In an alternative, but otherwise similar. approach detent 173 has only six detent points for one rotation of shaft 167 and the ratio between gears 168 and 169 is 14 to 1 while detent 163 has 14 detent points. In that case. there still are 84 total detent or switch points upon rotation of knob 166. but the number of channels jumped between each detent upon rotation of shaft 160 is reduced to six. Still other combinations are possible. For example. detent 173 may be assigned ll) detent points for each rotation of shaft 167. with the assigned gear ratio being changed so that it is nine to one and detent 163 having nine points. In that case. the number of channels jumped upon each detent of knob 161 is ID. Also. the number of total points of rotation of shaft 160 then is 90. so that a few additional unused points exist.

In FIG. 4.

shafts

160 and 167 are parallel to one another and spaced apart so that entirely

separate knobs

161 and 166 are appropriate. However. the coaxial knob and shaft arrangement of FIGS. Sa-Se offers the advantage of a more compact and convenient overall channel selctor. In this case. a UHF or fast tuning-knob 190 is coupled through

spur gears

191 and 192 directly to a fast-tuning shaft 193 that drives the movable switch contacts in network 150. As illustrated. a switch contact 195 is carried by shaft 193 to wipe central area 140 (FIG. 3). while another movable contact 196 electrically connected to contact 195 is positioned torotate over and thus wipe successive ones of the individual different fixed switch contacts distributed in an annular ring as shown in FIG. 3. Although not specifically shown in FIG. a. a second contact pair also preferably is carried on the rearward end of shaft 193 in order to widpingly connect annular ring 44 to the array of fixed contacts and thus complete the arrangement for connecting both ends of potentiometer 52 simulatneously across adjacent fixed contacts.

A VHF or slow-tuning knob 200 is coupled. through a gear system containing a spur gear 201 and another spur gear 202 together with a detent 203. to shaft 193. Also on the shaft carrying knob 200 and gear 201 is another detent 205. Detent 205 is of a simple ball and rippled wafer type construction as shown. On the other hand. and as detailed in FIGS. Sc-Se. detent 203 includes a ball 208 which may be received in any ofa plurality of seats 209 distributed around one lateral face of a hub integral with shaft 193. A spring 210 riveted at one end to gear 202 and retained in place by a C- washer 211 yields upon the turning of knob 190 so as to permit shaft 193 to be turned while yet not causing knob 200 to be changed through

gears

202 and 201. On the other hand. upon the application of a turning force to knob 200. detent 205 yields so that shaft 193 is driven by way of

gears

201 and 202; in this case. it is detent 203 which does not yield.

Fixedly secured to the rear face of knob 190 is an indicator disc 215. For the case in which detent 203 has nine rotary postions. detent 205 has rotary positions and the ratio between

gears

202 and 201 is nine to one. the face of indicator disc 216 conveniently is divided into nine segments each containing 10 equal spaces. All of the different channels may then be distributed in order around the periphery ofdisc 215 so as to be indicated by a pointer 216. As before, knob 190 causes fast rotation and turns l/9 of a revolution for each detent. Rotation of knob 200 causes shaft 193 to be rotated by one increment or channel point at a time. Alternatively. the other detent and gear-ratio combinatins previously explained may be employed in the apparatus of FIG. 5.

LII

It will be observed that. as revealed in FIG. Sb. all channels. whether UHF or VHF. have the same ease of accessibility and indication upon using knob 200 and reading the channel number off the face of disc 215. Yet. the other knob offers the user the additional flexibility of being able rapidly to get from one place in the channel series to a widely separated place.

The various arrangements described. therefore. enable the arrangement of a teevision channel selector so as to have improved ease and accuracy of tuning and indication. When desired. access to different adjacent channels in both the UHF and VHF regions may be achieved by manipulation of but a single tuning knob. At the same time. however. rapid access also is provided to widely separated channels. As best illustrated in FIG. 3. advantage is taken of printed circuitry for achieving compact and yet convenient switch action and selction. Moreover. the different arrangements permit use of a single fine tuning control inboth the UHF and VHF regions.

While particular embodiments of the present invention have been shown and described. it is apparent that changes and modifications may be made therein without departing from the invention in its borader aspects. The aim ofthe appended claims. therefore. is to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. A television channel selector for tuning a plurality of channels of equal bandwidth in unequally spaced frequency bands. said channels being contiguous within each individual band comprising:

tuning means including at least one varactor as the frequency-determining element. the frequency determined being a function of the voltage presented to a terminal of said varactor;

a source of DC potential;

a voltage divider connected across said DC source and composed of a plurality of resistors connected successively in series with the junctions between successive resistors terminating in stationary contacts;

fine-tuning means including a potentiometer having a movable tap coupled to said terminal to supply a frequency-determining voltage to said varactor. and a pair of offset movable contacts. each connected to respective opposing ends of said potentiometer;

channel selection means for moving said offset movable contacts sequentially into engagement with adjacent ones of said resistors to adjust the level of said frequency determining voltage; and

means. coupled to said voltage divider. bridging those stationary contact which define adjacent ends of said unequally spaced frequency bands.

2. A television channel selector as set forth in claim 1, wherein said last-mentioned means comprise resistors selected to develop voltage differentials to enable said varactor to tune across the frequency gaps between said unequally spaced frequency bands.

3. A television channel selector as set forth in claim 2. wherein said voltage divider is formed on a ceramic

Claims

1. A television channel selector for tuning a plurality of channels of equal bandwidth in unequally spaced frequency bands, said channels being contiguous within each individual band comprising: tuning means including at least one varactor as the frequencydetermining element, the frequency determined being a function of the voltage presented to a terminal of said varactor; a source of DC potential; a voltage divider connected across said DC source and composed of a plurality of resistors connected successively in series with the junctions between successive resistors terminating in stationary contacts; fine-tuning means including a poTentiometer having a movable tap coupled to said terminal to supply a frequency-determining voltage to said varactor, and a pair of offset movable contacts, each connected to respective opposing ends of said potentiometer; channel selection means for moving said offset movable contacts sequentially into engagement with adjacent ones of said resistors to adjust the level of said frequency determining voltage; and means, coupled to said voltage divider, bridging those stationary contact which define adjacent ends of said unequally spaced frequency bands.

3. A television channel selector as set forth in claim 2, wherein said voltage divider is formed on a ceramic substrate.