US 2392665 A
Description (OCR text may contain errors)
Jan. 8, 1946. e. E. GUSTAFSON 2,392,555
" RADIO RECEIVING SYSTEM Filed se t. 27, 1943 s Sheets-Sheet 1 INVENTOR GILBERT E. GUSTAFSON HIS ATTORNEY Jan. 8, 1946. G. E. GUSTAFSON ,5
I RADIO RECEIVING SYSTEM Filed Sept: 27, 1943 5 Sheets-Sheet 5 INVENTOR GILBERT E. GUSTAF'SON BYWaQLQM.%-
HlS' ATTORNEY Jan. 8, 1946.
G. E. eusT FsoN' RADIO RECEIVING SYSTEM Filed Sept. 27, 1943 5 Sheets-Sheet 4 AUD.
GILBERT E. GUSTAFSON laws d4; nwam I HlS ATTORNEY Jan. 8, 1946 G E. eusTAFsoN RADIO RECEIVING SYSTEM 5 Shets-Sheet 5 Filed Sept. 2'7, 1945 INVENTOR GILBERT E. GUSTAFSON &7M% HIS ATTORNEY Patented Jan. 8, 1946 RADIO RECEIVING SYSTEM Gilbert E; Gustafson, River Forest, 111., assignor to Zenith Radio Corporation, a corporation of Illinois Application September 27, 1943, Serial No. 503,868
This invention relates to radio apparatus mounted in an automobile. I
It is desirable to mount a radio receiver in a vehicle where it is convenient to observe indications on the dials thereof and yet where it occupies a position not necessary for other purposes and where the receiver is less apt to respond to extraneous annoying radiations.
It is also desirable to mount a radio receiver in a vehicle, such as an automobile, in such a position that the antenna leads thereto are of shortest possible length whereby leadin capacity is minimum. When so placed, mounting of the antenna is facilitated and the antenna leadin or antenna structure is less apt to impair the vision of the occupants of the vehicle.
It is also desirable to mount a radio receiver in a vehicle in such a manner that sound waves are directly transmitted to the listener without the loss of high frequency components which occurs when the sound waves reach a listeners ear by reflection from surfaces which usually reflect low frequency sound waves more than high frequency waves. 1
In the manufacture of radio apparatus for mounting in a vehicle, it is highly desirable that the radio apparatus may be manufactured, adlusted and calibrated in the factory and then placed in the vehicle without necessitating changes in adjustment or calibration. One of the most serious causes for making such additional adjustment after the apparatus is mounted in the vehicle is due to the antenna leadin. This is particularly true when the leadin is relatively long.
Furthermore long antenna leadins are usually formed with wire covered with a rubber cover and a connection shield braid. When the inner conductor is bent or kinked in manufacture, or where the leadin is bent in installation, the inner conductor usually is pressed near the outer shield braid so that stray capacity is increased.
- f importance is the fact that such long, bent leadins change their conformation as they age and as they are subject to vibration, and accordingly, change the stray capacity over a wide range, necessitating correspondingly'large and frequent changes of adjustment of trimming capacity in the first tuned circuit of the receiver connected to such long leadin.
When the antenna leadin is relatively long its electrostatic capacity to various parts of the vehicle serves as an impedance for the introduction of voltages of noise frequency into the signal amplifying channel of the receiver. These voltages of noise frequency may, for example, be hash produced by a conventional vibrator power supply or electrical disturbances produced by the ignition system of the vehicle. These voltages of noise frequency induced in the antenna leadin may in some instances be eliminated by shielding the antenna leadin, by providing a modified bridge circuit for balancing out the effect of the voltages of noise frequency on the radio apparatus, or loy'filtering means. In each case, additional equipment is necessary and usually the adjustments necessary for suitable performance are different for different vehicles of the same nominal design and construction. Further, in some cases, large noise voltages, such as'may be induced by ignition or the like, cause currents in, the shield of the leadin such that intolerable noise voltages are induced in the leadin itself.
In addition to affecting the signal to noise ratio of the radio apparatus, the antenna leadin affects the performance of the radio receiver 'in reproducing signals transmitted from a broadcast station and especially the ganging of the tuning elements of the apparatus, the frequency selectivity of the apparatus, the frequency calibration of the apparatus, and loss of efficiency results due to the bad power factor of the insulation of the leadin under certain climatic conditions.
When the leadin to such radio apparatus is long or has large capacity, tuning of the first receiver circuit is made more diflicult where capacity variation is used for tuning. In such apparatus, reduction of leadin capacity not only reduces loss of signal through insulation but also reduces the minimum circuit capacity so that capacity tuning is easier and the antenna tap on the input tuning coil may be moved up to increase signal transfer.
The services of a trained person are usually required for the installation and adjustment of V the radio apparatus in present day vehicles.
It is, as pointed out, desirable to connect the antenna of automobile radio apparatus as close to the apparatus as possible, and it is also desirable for attaining economy and enhancing performance to use as few circuit elements as possible in coupling the antenna to the grid circuit of the first discharge device in the apparatus. For that reason, among others, it is desirable to tune a capacitive antenna by inductance means, since, of course, it is necessary to have both inductance and capacitance in a tuned circuit. Therefore, an object of my invention is to mount a radio receiver in the header space of present such installation.
' of a modification of day vehicles, to supply the apparatus with radio energy from a capacity antenna and to tune the apparatus by using a variable inductance.
Another object of my invention is to provide an improved arrangement of a radio receiver in a vehicle so that all the above mentioned advantages are attained, and such that the receiver is positioned where the acoustical properties are optimum.
Another object ofthis invention is to mount the tuning means of a radio receiver in the header of an automobile and to provide means for man- Figs. 13 and 14 illustrate various control arrangements and switching means therefor useful in connection with the apparatus illustrated in Figs. 1 through 5.
Referring to Fig. 1, a header enclosure member or plate In extends substantially the full width of an automobile, upon which plate is fixedly mounted a complete radio receiverplaced between the metalrroof II which serves as a shielding element and header plate It. The space which the radio receiver occupies is usually called the header space and in the conventional presentually tuning the receiver, and for tuning the receiver by a switch remote from the receiver.
. A further object of my inventionis to provide such an arrangement in which the remote switch mutes the loudspeaker of the receiver, or in which the remote switch both mutes the loudspeakerand tunes the receiver, or in which the remote switch alsg adjusts the volume of the loudspeaker outpll It is another-- object hi my invention to provide a. radio r ceiver which is more easily installed in-a car and which isv more easily adjusted durin Another object of myinvention isto provide improved radio apparatus mounted in the header space of present-day-automobiles, which apparatus is substantially free of the detrimental effects resulting from the use of antenna leadins,
with substantial stray capacity.
Anotherobject of my invention is to provide radio apparatus mounted in the header space of present-day automobiles for use with an antenna m unted near the header Space and having a.
short, low capacity leadin.
Yet another object of my invention is to position a radio receiver'in the header space of an automobile and connect it through a low capacity leadin 'to' a capacity antenna which is tuned to,
stations by means of a variable inductance.
Still another object of 'my invention is to provide' a mounting for a radio receiver in an automobile wherein the receiver is better shielded from extraneous noise currents and voltages.
' ,The features of my invention which I believe to be novel are Isetforth with particularity in the appended claims.
My invention itself, both as to its organization and manner of operation, together with further objects and advantages thereof, may best be understood'by reference to the 7 following description taken in connection with the accompanying drawingsin which: 7 Figure 1 illustrates a'view, partly in section, of an embodiment of my invention;
Fig. 2 is a view of certain parts illustrated in Fig. 1, taken from a difierent angle; Fig. 3 is a side view of certain parts illustrated in Fig. 1; a
Fig. 4 illustrates an automobile and includes an embodiment of my invention;
Fig. 5 is a sectional view, taken from the side, the arrangement illustrated in'Fig. 1;
' Fig. 6 is a view, partly in section, of a modir, 'fication of that part of my invention illustrated in Fig. 4 as an antenna; r I
Fig. 7 is aschematic diagram of a circuit and certain associated parts especially suitable for use with my invention as illustrated'in Figs. 1 and 2;
the apparatus illustrated in Fig. '7;
Figs. 9 through 12 illustrate various circuit ar- V Fig. 8 is a detailed view of a certain partof day automobile is the space defined by the roof of the automobile and decorative felt or cloth directly in front of a person when he is sitting in the drivers seat. -'The radio receiver and its supporting means are positioned in th header space So as to give a pleasing appearance without sacrificing the space normally required for a conventional rear vision mirror M.
Although I prefer to mount the radio receiver in the header space, the receiver may be mounted elsewhere in the space normally defined by t e roof of the-automobile II and decorative cloth or felt l2-without projectin unduly far from the surface definedby the decorative felt. In such case the antenna should be mounted on the vehicle roof near the tuner of the receiver and a short, low capacity leadin be used; Alternatively, the adjustable tuning part of the receiver may be so mounted near the antenna-so that a short low capacity leadinfmay be used, and part or all of the rest of the receiver may then be but elsewhere. 1. q 7
I I prefer to mount all 'ofthe componentsof the radio receiver on the singleiunitary enclosure member orplate H) which may bemade of-pleasing appearance as shown. i'nthe copending design patent application Serial .No. Ill-110,425 .of Robert D. Budlong, filed'June, 10, 1943, and assigned to the assignee .of this app icat o This plate is easily mounted in and dismounted from the automobile. It is realized that the header enclosure member or plate H] may comprise more .than one. plate and that the header plate ii). may extend .onlya fractionalipar tiof the width of the automobileinstead' of substantially the full width asshowninLFig. 1.1; a.
The mainoperating elements of a conventional radio receiver, with, the exception'of antenna 13 (Fig.4) and speaker. I4,.are mounted in are ceiver unit 15 (Fig. ,3)1withmanual tuning means .IB' and volume control Imeans l1 projecting I l9 and EA and the plate iil then fastened tothe automobile'byfastening means or screws [93 so that the plate 10. close-soft the header spacewith the. component'sioff the radio receiver. confined therein. 1 ,Plate [0, preferably of pleasing appearance, a a s f cpen as ilA' which readilyallow the p s ge o so nd waves into, the car from the front'side'of the spea er lAjmountedIon'plate 10 direct hehmdppeniriss HlA. irie ibi i l eds side for enhanced low frequency response.
l8 supply speaker l4 with audio current from receiver unit l5. 1
A set of openings 103 through the left hand side of plate H) in Figs. 1 and 2 is symmetrically I located with respect to the other set of openings IOA about an axis passing through the longitudinal center line of the car. Since the header enclosure member or plate I closes oil? completely the space within which the speaker I4 is located, it is desirable when that header space is large to provide openings IDB in plate In so that a listener may hear sound waves from the rear side of the speaker as Well as from the front In instances where the header space is relatively small, it has been found desirable to close up the openings [0B for optimum tone quality withoutaltering substantially the general outer appearance of plate It].
The plate H) may extend only far enough back toward the front seat of the automobile to cover the front part of the header section as shown in Figs. 1 and 2 or may extend back a greater distance, as shown in Fig. 5, to a supporting member 24 rigidly mounted in the automobile.
Under certain circumstances the tone quality of the radio receiver is enhanced by making the air space in the header space within which the receiver is disposed of suitably large volume. For instance, sound baffle 20 in Fig. 5 is 50 positioned on its supporting plate ID that the position of the baffle determines the volume of air. entrapped in the header and hence the acoustical properties of the radio receiver. Baflle 20 is formed integrally with the plate ID or fastened thereto by fastening means such as screws (not shown).
Besides serving as a supporting member for the radio receiver, plate It to some extent serves'as a sounding board for sound variations produced by speaker I4. That is, the dimensions of plate In, which carries the radio receiver and forms a closure member for the header space, affect the quality of sound heard by a listener.
It may be desired to utilize the sounding board characteristic of plate It). In such case, the thickness of the plate should not be too large and the connecting leads l8, 2| and 22 connected respectively to the speaker 14, the fixedly mounted antenna l3 and control apparatus (described later) should be flexible so as to produce little restraining veifect on the vibrational movement of plate l0. It is preferred, however, to make plate l0 relatively rigid, so that the baffled space between plate lil, roof II and bafile 20 is resonant at a relatively low sound frequency.
The entire radio receiver is mounted in the header of an automobile in such a manner that there is enhanced tone quality of sound reproduction and in such a manner that the entire radio receiver together with its effective air chamber for determining the quality of sound reproduction is easily removed from the automobile, for example, by removing fastening means or screws [9B in Fig. 2 and screws 23 in Fig. 5.
An important feature of my invention is'that annoying extraneous radiations from the motor and other sources have little effect on the sound reproduced by the radio receiver because of the location of the radio receiving apparatus. Ignition voltage present on conductors in any region near the engine and instrument panel is high and it is accordingly desirable to place a radio receiver, highly sensitive to such undesirable voltages, far from such locations. The header'space radio receiving apparatus.
is desirably free from such voltages. Moreover, another feature of my invention i that the receiver is mounted in a position where an antenna having a short leadin may be used; that is, 9. capacity antenna, such as a fish pole antenna l3, which is mounted above the header space in insulating member 25 is used to great advantage. Also, since the capacity of the leadin is small, a loop antenna l3A, Fig. 6, of the directional or substantially non-directional type is also used to advantage. That is, a loop antenna l3A encased in a streamlined insulating housing BB is mounted on the automobile roof I I and supported by elastic insulating material 25 above the header space for connection to a radio receiver in the header space.
The receiver unit I5 is preferably tuned by means of a turret tuner of the type shown and claimed in United States Letters Patent No.
2,310,720 issued February 9, 1943, to Clarence W. Wandrey and assigned to the same assi nee as the present application. The particular tuning means used to tune the apparatus in receiving unit I5 is shown in Fig. '7.
receiving apparatus is tuned sequentially to one.
of a plurality of frequencies by sequential operation of a footswitch 32 controlled by the driverof the automobile, or tuned selectively and non-sequentially by actuating one of a series of switches 26, 27, 28, 29, 3B and 3| located on the header plate It, or at the dashboard or other convenient place in the automobile. The arrangement illustrated in Fig. 7 tunes the apparatus in receiver unit l5 either upon actuation of the manual tuning knob I6, the footswitch 32 or any one of the selecting switches 26 to 3|.
The receiver mounted in the header of the automobile is otherwise generally of conventional type and is preferably of the type which is tuned by inserting a member of relatively high permeability into a tubular inductance coil in such a manner that the inductance of the coil depends upon the relative position of the coil and high permeability member.
- The inductances of coils 33 and 34 (Fig. 7) determine the frequency of the received signal and these inductances are varied respectively, by adjusting the position of members 35 and 36 of relatively high permeability with respect to coils 33 and 34. Only two tuning inductance coils are shown in Fig. 7 for simplicity but it should be understood that more than two and preferably three or four of such coils are tuned simultaneously by positioning relatively high permeability members similar to members 35 and 36 with respect to inductance coils which are connected in the The tuning members or control members, such as members 35 and 36, are carried on a movable carriage 31, which is secured upon a rod 38 connected to a movable solenoid core 39. The rod 38 has its forward end 40 bent so as to cooperate with one of a plurality of stops or abutments 4| of the assembly 42; and these'stops 4| are adjustably held in a turret .member 43 by cooperating screw threads on stops 4| and turret member 43 (Fig. 8).
The turret member 43 is secured upon a rotatable shaft 44 which'carries a ratchet wheel 45 otally mounted on an arm 41 which swings about the shaft 44 and is pivotally and slidably connectedto one arm of "a bell crank 48 having its other arm pivotally and slidably connected to a lever member 49, the latter being pivoted on a fixed pivot pin The lever member 49 extends from its pivot pin 5| and has a slot52 to accommodate a pin 53 securedupon the rod 38. The upper end of thelever 49 is preferably positioned so as to'bevisible and cooperates with a scale 54 having suitable graduations thereon whereby a suitable indication of the position 'of rod 38 and tuning members 35 and 35 is obtained. a r
With the-apparatusthus'far described in Fig. 7, itis clear that when rod 38 moves to the left in the direction of its axis, the bell crank '48 rotates behind an. adjacent tooth on the ratchet wheel 45, and that when the rod 38 returns to the right the ratchet wheel 45 is rotated one sixth of a revolution to a position where an adjacent stop 4| on turret 43 limits-further-movement of the rod 38 and'in'ductance tuning. members. 35 and V .36 carried thereon. Themanner in which the solenoid core 39 and associated rod 38 are actuated by electromagnetic means is described here- .inafter. 1 a a 1 Upon turret shaft 44 is mounted homing device .55 having a rotatable and grounded electrical con- .tact making member 56 whichrotates When andv asturret shaft 44 rotates for effecting suitable .electricalswitchingn Homing device 55 has six equally spaced fixed contacts 26A, 21A, 28A, 29A,
.30A and 3|A arranged so that when the turret 43 is in one of its six positions corresponding to the position wherein rod 40 engages one of the stop members 4|, thecontact making member 55 the homing device.
Each one of the contact members 26A, 21A, 28A, 29A, 30A and 3 IA is connected to a respective nor- -mally closed. stationary contact on a respective one of thestation selecting switches 26, 21, 28, 29,
engages one of the fixed contacts 26A to 3|A on .3|land.3|; and the other'contacts 26B, 21B, 28B,
29B, 35B and 3|B, which. are movable, are each connectedto aLcommon low-resistance conductor .51.. ,Each one. of the selecting switches 25 to 3| has a normally. open .fixed contact connected't'o corresponding contacts on the other selecting switches by means of low resistance connection 58 whichisalsoconnected to one terminal of a voltage source 59. The other terminal of voltage source 59 is connectedto a terminal of actuating solenoid 64 which has its other terminal con- ,nected .to ground through an automatically operated position responsive switch 6|.
Thus, when one of the selecting switch contact members'ZSB to 3 |B,for example, switch contact member 25B, is moved from its normally closed position to the position where it engages contact 280, current flows from one terminalof voltage source 59 through solenoid actuating winding 50gswitch 6|, ground, arm 55, contact 3 IA, the normally closed contacton electric switch 3|, movable contact 3|B, conductor '51, movable contact 253, and the normally open contact 26C on selecting switch 26 back to the other terminal of ,voltage source 59.
When solenoid 6|) is energized, for example, by thus producing a current flow through the normally open contact 26C on switch 26 in theman- .ner described above, solenoid core 39 and rod 38 are moved to the left in Fig. 7 to a position where solenoidextension 62, of insulating material, en-
gages and actuates the switch 5| from circuitcl'osin'g position to circuit opening position and thus opens the circuit to solenoid winding 6|) and in so doing allows solenoid core 39 to return to its furthermost positionto the right under'the' In the return movement of rod 38 to the right, in order to be sure that the rod 38 moves sufficiently far to the right to move the ratchet wheel 45 one sixth of a revolution before the solenoid is energized again through switch 6|, time delay means 65, illustrated as a fluid dashpot, are connected to the resilient movable con-'- tact of switch 6|, which time delay means delays reclosing of the switch 6| after it has been opened by member 62. It is clear that the time delay means 65 may take other forms than the liquid dashpot shown in Fig; 7.
The liquid dashpot as illustrated has a movable piston 65 with an orifice 51 for controlling the speed of piston travel to the right in Fig. 7; A'second and larger piston orifice 68 is opened by conventional means (not shown) only when the piston moves to the left in Fig. 7 in cooperating cylinder 69 so that the piston 56 may move faster to the leftthan it moves to the right with the same forces applied thereto. a
In summary, when it is desired to select one of a plurality of broadcast stations determined by the relative position of a particular stop member 4| in turret member 43, one of the switches 26 to 3| correspondingto that particular stop member is actuated so as to energize solenoid 60. When solenoid 60 is energized due to current flowing from voltage source 59', solenoid rod 38 is moved to the left against the action of tension spring 64, and pin 53 on rod 38 engages lever 49 which pivots around its pivot pin 5| so as '40 to rotate the bell crank 48' counterclockwise ing of switch 6|, tension spring 54 causes clock-,
wise movement of lever arm 4! and causes the turret 43 to be moved an angular distance corresponding to the angular distance between teeth on ratchet 45 which distance. corresponds to the angular distance between stops 4|.
Such action continually repeats itself until wheel 45 and stops 4| together with arm 58 are turned to the fixed contact connected to that one Of-SWitChESlfi to 3| which is actuated, and at that fixed contact; the circuit through the switches 26 to 3! being broken byits actuation,.
the repeated action stops'and the desired station isv selected. a
Stops 4| are adjustably mounted in turret mem- 5 her 43 and the relative position of eachparticular stop 4| in turret member 43 determines the distance tuning members 35 and 36 project respectively within inductance coils 33, and 34 after the turret member 43 is rotatedaround to a position where that particular stop limits movement of rod 40. g V a 7 It isthus clear that when one of the switches 26 to 3| is actuated theturret member 43 is rotated, due to current flow throughtsolenoid 60, which current "also. flows intermittently through the normally'open'contact of thatpar-' ticular switch and the normally closed contact of the other switches until the rotating contact 56 of homing device 55 engages one of the contacts 26A to 3IA corresponding to the switch which is actuated. When the rotating contact 56 engages the stationary contact corresponding to the particular switch actuated, then current flow to the solenoid 66 is interrupted. That is, when switch 26 is actuated turret member 43.is
rotated until rotating contact 56 engages con-,
tact 26A, and when switch 21 is actuated contact. 56 stops at contact 21A, etc.
It is also clear that when footswitch 32, which is connected in a series circuit with source 59 and solenoid 63, is closed solenoid 66 draws the core 39 to the left and causes the turret member 43' 1 to rotate one step corresponding to the angular distance between stop members.
Therefore, in order to tune the receiver by actuating the footswitch 32, it is necessary that moved to make contact with stationary contact 26C and the receiver is tuned without further actuation of switch member 263.
the signal is reproduced by speaker I4. I prefer to tune the receiving apparatus, particularly the antenna circuit, by means of variable inductance.
.Signal voltages appearing between antenna I3 and ground in Fig. 11 are impressed across the parallel resonant circuit including adjustable trimmer condenser I 26 connected between antenna I3 and ground and variable inductance 33 and coupling and isolating capacitance H5 connected in series between antenna I3 and ground, the condenser I I 5 having one of its terminals connected to ground. The signal voltage developed across coupling capacitance H5 is applied between the grid and cathode of radio frequency amplifying discharge device .I I6 through the second variable inductance 34 and low reactance bypass capacitance H8, the inductance 34 being connected between the control grid of discharge device H6 and the junction point of inductance 33 and capacitance I I5, and capacitance I I8 being connected between ground and the cathode of discharge device H6.
Trimmer capacitance |2I is connected in parallel circuit relationship with inductance 34, between the grid of discharge device I I6 and ground, to form a resonant circuit with inductance 34 and serve, together with condenser I26, as a means for Other time delay switching means, similar to i the dashpot means shown in Fig. '7, may be used as shown in the copending application of,0tto E. Wagenknecht, Serial No. 503,878, filed on even date herewith and assigned to the same assignee.
The receiver may be also tuned manually at the header plate ID by turning tuning means- 4IA which, as shown in Fig. 10, is threaded onstop member 4| and is confined within a hollowportion of turret member 43 between walls 43A and 43B. Conventional means, not shown, is provided to prevent rotation of stop 4| within member 43 when gear MA is turned. When knob I6 is turned manually, the stop 4| is turned in or out of turret member 43 in a direction depending upon the direction of rotation of knob I6; and rod which is pressed against stop 4| by tension spring 64 follows the movement of stop member 4|. The position of rod 40, as explained previously, determines the inductance of coils 33 and 34 and hence the tuning of the receiver.
In addition to serving as a manual tuning means, the knob I6 may beturned to adjust the position of the other stop members 4! in turret 43 so that the stop members 4| may be in suitable position for tuning when the footswitch 32 or one or switches 26 to 3| is actuated.
The switches 26 to 3| shown in Fig. 7 may be of the pushbutton type and 'may be mounted on header enclosure member ID, or on the instrument panel of the automobile or otherconvenient place.
Fig. 9 shows schematically the circuit of the radio receiving unit I5 located in the header space of a vehicle as in Fig. 3. Modulated radio frequency signals received on antenna I3 are applied to a superheterodyne receiving circuit in such a manner that the modulation envelope of providing a tuning and tracking adjustment when, asin mass production, an antenna having'unpredictable characteristics is mounted on the automobile.
Radio frequency amplifying discharge device I I6, of the variable mu type, is supplied with space current frornvoltage source I22, whose negative terminal is connected to ground and whose positive terminal is connected to the anode of discharge device I I6 through a primary transformerwinding I23. The cathode of device H6 is connected to ground throughresistance I24, bypassed for highfrequency current by condenser H8. The screen rid of discharge device I I6 is connected to the positive terminal of voltage source I22 and is maintained at cathode potential for voltages of frequency corresponding to signal frequency by capacitance I25 which is connected between the cathode and screen grid. Discharge device I I6 is preferably of the pentode type'having its suppressor grid connected to its cathode. The grid of discharge device H6 is maintained at a minimum negative potential with respect to its cathode in conventional manner by the direct current voltage drop across resistance I24, which voltage drop is produced by anode and screen grid current flowing through resistance I24. Low reactance bypass capacitance H8, in conventional manner, is connected in parallel circuit relationship with resistance I24 so as to provide a low impedance path around resistance I24 for signals of frequency corresponding to the carrier frequency; T
Radio frequency signals amplified by discharg device H6'are applied to the primary winding I23 of transformer I21, whosesecondary winding I28 is coupled to another radio frequency amplifying stage I29. Signals from radio frequency amplifying stage I29 are then, in turn, 'in conventional superheterodyne fashion, applied to an oscillator-modulator stage I36, an intermediate frequency amplifier stage I3I, a detector stage I 32, and then to an audio amplifying stage I33 which is coupled to speaker I I.
An amplified radio frequency voltage from the input to the detector stage I32 is applied between the anodeiand 'cathode'of rectifying device I36 through capacitance 13'! for the production of a unidirectional potential for controlling the. gain of the receiver. That is, an automatic volume control. .(A. V. C.) is provided. The unidirectional voltage developed across. resistance I38 which has one terminal connected to the anode of discharge device I36 and the other :terminal connected to the grounded cathode is filtered. by means of filter capacitance I39 and resistance I40, acting together with condenser I I5, and then applied between the. grid and cathode of radio amplifying'device IIB. In the particular arrangement shown in Fig. 9, the automatic volume control' lead I42 having one terminal connected to a point on resistance I38 through filtering resistance I49 has'its other terminal connected to the junction point of coupling and isolating capacitance H and variable inductance 34. The cathodes. of discharge devices I I6 and I36 each have a direct current. path to ground so that the potential of lead I42 effects a change in grid bias voltage of device II6. Since discharge device H6 is of the variable mu type, the degree of amplification produced thereby is dependent upon the direct current potential of lead I42 with respect. to ground, or is dependent upon the amplitude of amplified radio frequency voltage.
Fig. 10 shows another inductance tuned circuit for coupling antenna I3 directly to the grid of the first radio frequency amplifying device I I6, when, as in this instance, the antenna leadin capacity is very small. The radio frequency voltage appearing between the antenna I3 and ground is applied to a series circuit including variable inductance 33 and low reactance isolating capacitance. I44. Trimmer capacitance I45 connected across terminals of variable inductance 33 serves as a means for providing a tuning'adjustment, when as in mass production, an antenna having unpredictable characteristics is mounted on the automobile. The A. V. C. lead I42 is connected to the junction point of inductance 33 and capacitance I44.
In the arrangement shown in Fig. 10, substantially all of the voltage appearing between antenna I3 and ground is applied between the grid and cathode of discharge device II B. The grid is connected directly to the junction point of the antenna I3 and variable inductance 33 and the cathode is connected to ground through the low reactance bypass capacitance IIB. When the antenna leadin is long and has a comparatively high capacity to ground, it is usually undesirable to couple the antenna directly to the grid of discharge device III; as shown in Fig. 10. In that case, the antenna coupling arrangement shown in Fig, 14 and described hereinafter is more desirable. With such a high capacity lead in, the arrangements of Fig. 9 or 10 could be used if the antenna trimmer condenser I 20 or I45, respectively, were connected in series with the antenna I3, with a corresponding loss of signal.
One of the important features of this invention is that, when the antenna leadin capacity is small, the antenna couplingand tuning arrange-- ments are simplified. This is particularly true when a variable inductance is used to adjust the resonantfrequency over a given band of frequencies, because a capacity antenna tuned with a variable inductance does not increase minimum circuit inductances'and so does not decrease the maximum tunable frequency in the frequency range. a
When a capacity antenna is tuned with adjustable capacity, most small antennas being capacitive, conditions are not so favorable, but are greatly improved by the use of my arrangement with a short leadin of low capacity. Minimum circuit capacity includes antenna capacity, lead.- in capacity, and the minimum tuning condenser capacity, all of which acts to reduce the maximum tunable frequency. When leadin capacity is reduced as in my arrangement, the reduction of maximum tunable frequency is minimized. This minimizing of minim-um circuit capacity by reducing leadin capacity and loss also makes it possible to connect the antenna tap higher up' In the modified arrangement shown in Fig. 11,
substantially all of the voltage appearing between antenna I3 and ground is applied between the grid and cathode of discharge device H6 and the antenna input circuit is tuned to a station in the broadcast band by variable capacitance I41. The voltage appearing between antenna and ground is applied to the series circuitincluding fixed inductance I48 and capacitance I49, and is then applied between the grid and cathode of discharge device II6 through I ow reactance bypass capacitance II 8. Tuning capacitance I41 and trimmer capacitance I5I are connected in parallel circuit relationship with each other and in parallel with the series circuit including fixed inductance I48 and isolating capacitance I49. The A. V. C. lead I42 is connected to the junction point of inductance I48 and capacitance I49. Such an arrangement Withantenna I3 connected to the grid of device II6'di'rectly can be used over a wide tuning range only when leadin capacity, and therefore minimum circuit capacity, is minimized in accordance with my invention.
In comparing the inductance tuning arrangement shown in Fig. 10 and the capacitance tuning arrangement shown in Fig. 11, it is noted that one additional element, the trimmer I 5 I, is required in the arrangement shown in Fig. 11. Also, the ratio of inductanceto capacity in the tuning arrangement shown in Fig. 10 may be greater than the equivalent ratio of the tuning arrangement shown in Fig. 11, and the'circuit impedance is correspondingly higher, resulting in greater signal voltage gain. Moreover, the signal to noise ratio of the receiver incorporating the inductance tuning arrangement shown in Fig. 10 is higher and more constant over the tuning range than the receiver incorporating the capacitance tuning arrangement shown in Fig. 11.
Fig. 12 shows another antenna couplin circuit tuned by a variable inductance. The voltage appearing between antenna I3 and ground is applied through a coupling condenser I58 across condenser I 54 of relatively high capacitance. The voltage developed across capacitance I54 is applied between the grid and cathode of discharge device IIB through variable tuning inductance 33 and low reactance bypass capacitance II8, the inductance 33 being connected between antenna I3 and'the 'grid of discharge device II 6, and capacitance II8 being connected between ground and the cathode of device I I8.'
Trimmer capacitance I56 connected between the rid of discharge device H6 and ground com-.
pletes the tuned circuit I3, 33, I54 and I56 and serves as a means for providing an adjustment, when as in mass production, an antenna having unpredictable characteristics is mounted on the automobile. The A. V. C. lead I42 is connected to the grid of discharge device H6 through inductance 33 and is bypassed to ground for high frequency currents through capacitance I54.
It is understood that the complete radio receiving unit I5 mounted in the header space includes all of the elements shown in Fig. 12 and also may include conventional means, such as a vibrator power supply (not shown), for converting into a high continuous voltage the low continuous voltage of a conventional automobile storage battery for supplying space current to the discharge devices. The battery is located in its conventional place in the automobile and is preferably connected to the receiver unit I5 by a conventional electric plugin connection.
Alternatively, the unit I5 mounted in the header space may include only device I I6, the
. amplifier I29, the frequency converter I39 and the associated circuits, the remainder of the complete receiver being placed elsewhere in the vehicle.
The header plate I and baflle 20 are of electricity conducting material and the components in receiving unit I are encased in a box of electricity conducting material. The roof II of the automobile is of electricity conducting material and as a consequence, in the arrangement shown in Fig. 5, the elements in the receiving unit I5 are doubly shielded. That is, the metal box encasing the receiving elements in receiving unit I5 comprises one shield and the metal plate I6, roof II and bafile 20 form another shield. The plate I9, baflie 20 and roof II may be bonded together electrically by means of low electrical resistance connections. The metalbox enclosing the receiving unit I5 of course serves as a good electrostatic shield for preventing an electrostatic component of noise voltages from being induced in the elements in unit I5, but by providing doubly shielded arrangement as shown in Fig. 5 the elements in unit I5 are effectively shielded also from the influence of the magnetic component of noise voltages. In addition, the metal plate I0, baffle 20 and roof II form an electrostatic shield for leadin 2 I.
It is understood that the switch 32 shown in Fig. '1 is a footswitch operable by the driver of the automobile and may .be of the type disclosed in the patent of Eugene F. McDonald, Jr., Number 2,216,671, issued October 1, 1940. Alternatively, the switch 32 may be a push button type-of switch having features of the footswitch shown in the McDonald patent and being mounted on the plate I0.
' The volume of the audio signal reproduced by speaker I4 may be controlled by an arrangement similar to one disclosed in the copending application of Eugene F. McDonald, J r., Serial Number 468,478, filed December 10, 1942. That is, the
volume may be controlled either by manipulating knob I1 on plate In orby operating a foot control operable by the driver of the vehicle.
Fig. 13 shows an arrangement wherein the output volume of signals reproduced by the receiver mounted in the header space is controlled by manipulating knob I1 at the header space or by actuating a member,'preferably a foot control member, located at a remote point. I
stalled in the header space of the automobile in cludes antenna I3, a selective tuner mechanism,v
amplifier and power supply representedby a rectuner and amplifier I65, a power amplifier discharge device I61 and speaker I4; The operation of the radio receiver is normal insofar as'it successively receives a modulated carrier wave fromthe antenna I 3, tunes and amplifies suchwave through the tuner and amplifier I65, detects the signal in accordance with which the carrier wave is modulated, such detection being carried out in the circuits associated with the discharge device I66, amplifies such signal through devices I66 and I61, and reproduces the signal in speaker I4.
The signal detection circuit associated with the discharge device I66 includes a high frequency transformer I68 whose primary winding is energized by the amplified carrier wave from the tuner and amplifier I65, the secondary of transformer I68 being tuned to resonance at the frequency of such carrier wave by a capacitance I19. One terminal of the secondary of the transformer I68 is connected to the anode I1I of a diode section of the electron discharge device I66 andthe other terminal is connected for high frequency current through a capacitance I12 to the cathode I13 of the discharge device I66, which cathode is associated with the diode section including anode I'll, and with the triode section including a con-' trol electrode I14 and an anode I15. To complete a path for a continuous current through the anode "I the cathode I13 is grounded, and that terminal of the secondary of the transformer I68 which is connected to the condenser I12 is grounded through two serially connected resistances I11 and I18. A point between resistances I11 and I18 is connected to ground and to the cathode. I13 through a high frequency bypassing capacitance I19, whereby signals detected in the detection circuit appear across the resistance I18.
The signal across the resistance I18 is transferred through either of two circuits to be de-' pacitance I89 to the control electrode I14 of discharge device I66. This control electrode I14 is connected through a suitable grid resistance I8I to the cathode I13. The anode I15 is connected through a suitable load resistance I83 to a source of positive potential illustrated schematically by the rectangle I65, which source of positive potential is supplied with power through a switch I84 from a suitable battery I 85 which may be the storage battery of a vehicle, such as the automobile mentioned previously.
Amplified signal potentials appearing across the load resistance-I83 are amplified further through the power amplifier discharge device I61, which is connected in usual fashion, and such amplified signals are transferred through an output transformer I94, the secondary of which is connected to energize the speaker I4.
One circuit for transferring signals from the resistance I18 to the control electrode I14 includes the volume control resistance I86, which is embodied in a unit I81, suitable for mounting near the feet of an operatorof the vehicle in which the receiver is mounted, The ungrounded terminal of the resistance I18 is connected through a switch I88, conductor I89, terminals I of a. plug I9I andsocket I92, and a conductor I93 to one terminal of resistance I86. The other ter- In Fig. 13, a radio receiver arranged to bein Ininal of resistance I86 is connected through a conductor I95 and terminals I96 of the plug I9I' receiver to produce undesirable current flow throughresistance I86, which would result in undesirable noise being produced in speaker I4."
The movable contact I91 of the volume control resistance I88 is connected through a con ductor I98, terminal I99 of the plug I9I and sock et I92, a switch 299, and condenser I89 to the control electrode I14. By such connections, signal-vol'tage appearing across the resistance I18 appears also across the volume control resistance I86, so that any desired portion of this signal voltage across" resistance I96 may be impressed through movable contact I91 upon control electrode I14, thereby controlling the output of speaker I 4, Suitable means are provided, as described in the copending application of Eugene F. McDonald, Jr., Serial Number 468.478, filed December'lO, 1942, to control the position of the movable contact I91 by foot operation of the vehicle driver.
In the unit including the foot operated volume control resistance I 86, there is also provided means operable by the foot of the vehicle driver for silencing the speaker I4 and for changing the tuning adjustment of the tuner represented by rectangle I65; This means includes a switch contact 202, movable by the foot of the vehicle driver, a second switch contact 283, movable when engaged with contact 282, and a third. fixedswitch contact 204. Contact 282 is connected through a:
conductor 266 and terminals 281 of the plug I9I and socket I92 to ground. The contact 284 is connected toswitch I B I'through a conductor 212, terminals 288 of the plug I9I and socket I 92, a conductor 289. and operating coil 66 of an electromagnet suitably arranged for changing the tuning adjustment of a selective tuner of the type previously described. The contact 293 is connected through a conductor 2I9 and terminals 2 I I of the plug I 9 I and socket I92, to oneterminal of the secondary of output transformer I 94. The other terminal of the secondary ,oftransformer In operation; the driverofa vehicle in which this receiver is installed may at will controlthe output volume of the receiver by moving by a foot operation the movable contact I91 of the resistance I 86, or he may depress the movableswitch' contact 282 until it touches contact 2 fl3, atwhich time a short circuit is placed across the seco-ndary of output transformer I 94 thereby instantaneously silencing the speaker I I. Such silencing is frequently desirable to allow a conversation .or to listen for a train whistle at railroadcrossings.
Further depression of the switch contact 292,.
so that it carries the movable contact 283 with it to complete a circuit between the contacts 203 and 264,.energizes the operating coil 68 from bate tery I85, so long. as switch I 84 is closed, to change the tuning adjustment of the tuner represented by the, rectangle I65 so as to receive a difierent station. I
Switches l84, I 88 and 208, as well as the mova ble contact 2M of the volume controlresistancel 2I5,, are mechanically arranged to be controlled by operation of a single operating element I1.
suchas shown in Fig. 14 and disclosed in the above mentioned 'copendingrapplication of En gene FaMcDonald. lTr., Serial Number 468,478, filed December 10; 1942, which element'is preferablyso positioned that it may be operated bya'n occupant of the vehicle other than the driver, and preferably so located that it also maybe operated by the driver. V
Upon initial movement of'the operating element I1 shown in Fig. 14 from one extreme position, the switch 1861s first closed without affectingswitches I63 and 280 so as to energize thereceiver power supply represented by the rectangle I65, and so as to connect the operating'coil 69 of the station selecting electromagnet in readiness for energization by the movabie contact 203 :in v
unit I81. A slight additional, inovementof this operating element I1 is effective then to change 2| 40f volume control resistance2i5 through ca-' pacitance I66 to the control electrode I14. Still further movement of this operating element leaves switches I84; I89 and 286 in the position, to which they may have been moved; and thereafter moves contact 2I4 along resistance 215 to increase that portion of the signal potential across resistance I18 which is applied through resistance 2 I5 to control electrode I14.
In Fig. 14 there is shown a side view of such an operating element, illustrated as a knob I1 which may suitably be turned by hand. This knob I1 is arranged to turn a shaft 216 on which is mounted the volume control resistance 2 I5 and switches I84, I88 and 260. This unit may be so mounted that knob I1 projects from the header plate ID as shown in Fig. 1, so that it may conveniently be operated by the driverof the vehicle or by a passenger.
In either of the two cases wherein the volume output of the receiver is controlled by adjusting the tap ZI I on resistance 2I5 or by adjusting the tap I91 on resistance I86, the detected and ampli fled signal from device I66 appears across anode resistance I83 which is connected between the anode I15 and the cathode I13 through low reactance bypass capacitances 228 and 22 I.
tively insensitive to voltages produced by currents of carrier frequency by connecting capaciand continuous current blocking capacitance 223 and capacitance 228, which grid is maintained at a suitable operating potential by connecting resistance 225 between the cathode of device I61 and ground and by connecting resistance 224 between the grid and ground thus utilizing the voltage drop occasioned by space current of device I 61 flowing through resistance 225 as grid bias voltage for device I61.
Discharge device I61 is preferably of the pen- .tode type having its suppressor grid connected to its cathode and with its anode and screen grid" The output circuit comprising resistance I83'is made rela mesa-cos at'substantially the same continuous current operating potential. -The highpotential"lead226 is connected to the screen grid, and to the anode through the low resistance primary winding of audio output transformer 194, It is understood that the high potential lead 226 is connectedto the positive terminal of a voltage source in unit I65, the other terminal of the voltage source being connected to ground.
In conventional manner, the cathode of device I61 is maintained at substantially ground potential for high frequency currents by connecting capacitance 22! of relatively low reactance between cathode and ground; and the screen and cath- =odeare maintained at substantially the same audio frequency potential by connecting capacitance 220 between the screen grid and cathode.
It is understood, of course, that the switch 32 shown in Fig. '7 may be mounted in 'any convenient place in the automobile, for example, on the header plate ill or on the dashboard of the automobile. Also, the composite switch and volume control shown-in a, single unit in Fig. 13 maybe mounted in any convenient place in the automobile, forexampleon the header plate II! or on the dashboard of the automobile. When the composite switch 230 shown in Fig. 13 is mounted on the header plate l-U, it may not be necessary to include the volume control 186 and in that case volume is controlled by manipulating knob IS in Fig. 1 and the switch 230 in Fig. 13 is efiective to mute and tune the receiver. I b
It is understood, or course, that the radio receiver mounted in the header space may be provided, in conventional manner, with a tone control which may be effected by manually operating push buttons mounted on the header plate l0.
It should also be understood that, while I have illustrated and described my invention in connection with a'radio receiving tuningunit mountf'ed in the roof. of a vehicle and connected through a very short, low-capacity leadin to an antenna mounted above the roof, 2. remote switch being provided to operate the tuning unit, the arrangement is equally useful in radio transmitters, the
tuning unit being utilized to adjust the output frequency of the transmitter.
While I have shown and described the particular embodiments of my invention, it will be obvious. to those skilled in the artthat changes and modifications may be made without departing from my invention .in its broader aspects, and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the truespirit and scope of my invention.
1.1 In combination, a radio tuning unit mounted s bstantially just under th metal roof of a vehiclebetween its roof and eiling lining, means arranged to hold saidtuning unitbetween said ef and linin a lo c paci y annanna mount d ab ve s d root and adja ent. said unit, and a leadin or low capa ity having aien th below said ro t less. thanthe distance between s id roo a c n and. connecting said antenna to s id tuning-unit. I V
'12. in combination. a radio tun g'unit mounted substa t a iy witlnnjtne. header space just und r 'th 'metalroof or a -vehi l between its roof and, il ng ng. means arranged. to hold said tuning unit between said. root nd l nin a lo ca acity ant nna mounted. above the roof or said vehicle adjacent sai header space, and a leadin 01 low capacity having al n th beiowiisald roof 'lessthan'the distance between said roof and ceil- :in and confined within ing lining connecting said-antenna to said" tuningunit.
3. In-combination, a radio tuning unit comprising a tuned circuit including an adjustable inductance and a capacity all mounted'substantially in the header space of a vehicle between its roof and ceiling lining, means arranged to hold saidtuning unit within-said header space, an antenna mounted above the roof of said vehicle adjacent said header space, and a leadin of low capacity having a length below said roof less than the distance between said roof and ceiling lining connecting said antenna to said tuning unit, said adjustable inductance being arranged to tune the antenna to a'frequency in an extended frequency range.
4. In combination, a radio receiver including a speaker mounted substantially in the header space of a vehicle between its roof and ceiling lining, means arranged to hold said receiver including said speaker within said header space, an antenna for the reception of radio signals m0lmted above the roof of said vehicle adjacent said header space, and a leadin of low capacity having a length below said roof less than the distance between said roof and ceiling lining connecting said antenna to said receiver.
5. In a radio system in a vehicle having a metal roof, a lining within said vehicle spaced just under said roof, a radio inductance tuning unit mounted substantially in thespace defined by said lining and roof, means holding said unit within said space, a low capacity antenna mounted above said roof adjacent said unit, and a leadin of low capacity having a length below said roof less than the distance between said roof and lining connecting said antenna to said unit, said radio tuning unit and leadin being sodisposed in close proximity to said roof that said roof serves as a shield for the radio tuning unit and leadin. v
6. In a vehicle having a metal roof and a header space, a complete radio receiver mounted substantially in and confined within the header space between the metal roof and vehicle ceiling lining, means arranged to hold said receiver within said header space, a low capacity antenna mounted on said roof above the header space for thereception of high frequency signals, said radio receiver being so disposed in close proximity to said metal roof that'said metal serves as a shieldhfor the radio receiver, and a short low capacity leadin having a length below said roof less than the distance between said roof and ceiling lining and connecting the receiver to the antenna.
"I. In a radio receiving system in an automobile, said automobile having a header space defined by the automobile' roof and ceiling lining, a complete radio receiving apparatus including a speaker and an input circuit confined substantially entirely within said header space, means means in the header space for tuning the antena input circuit. V a
8, In a radio receiving system in an automobil havin a header space, a complete radio receiver including a speaker mounted substantially the header space defined by the automobile roof and ceiling lining, means er space for the reception of high frequency sig nals, a short leadin of low capacity having a length below said roof less than the distance between said roof and ceiling lining and connecting the antenna to the receiver, and variable inductancetuning means located in the, header space and arranged for tuning the antenna.
9. In a radio receiving system in an automo bile having a header space,-ceiling lining, and a metal roof, a complete radio receiving apparatus including a speaker confined substantially entirely within said header space defined by said metal roof and automobile ceiling lining, means arranged to hold said apparatus within said header space, a low capacity antenna mounted on the roof above the header space'forthe reception of high frequency signals, a short leadin of low capacity having a length below said roof lessthan the distance'between said roof and ceiling lining and connecting the antenna to the receiver, said radio receiver and antenna leadin being located in close proximity to said roof whereby said roof serves as an electro-static shield for said radio receiver and antenna leadin, and variable tuning means within the header space for tunin the an-, tenna.
reception of highirequency, signals, a shortlead- 7 in of low capacityhaving a length below said roof less than the distance between said roof and ceil ing lining connecting the antenna to the receiver, variable inductance tuning means located inthe header space for tuning the antenna, saidradio 10. In aradio receiving system in a vehicle having a header space, a ceiling lining, and a metal roof, radio tuning apparatus confined sub stantially entirely within said header'space defined by said roof and ceiling lining-means arrangedto hold said apparatus within saidheader space, an antenna mounted on the roof above the header space for the reception of high frequency signalsa short leadin of low capacity having a length-below said roof less than the distance be- :tween said roof;and ceiling lining and connectingthe antennatothe receiver, said radio receiver and antenna "leadin being so disposed in close proximity to said roof that said roof serves as an electro-staticfshield for the radio receiver and antenna leadin, and variable inductance tuning means within the header space and arranged for tuning the .low capacity antenna to frequencies in an extended frequency range. a v
11. In a radio receiving system in an automobile,-said' automobile havingia header space, a
ceiling lining, and ametal roof,a complete radio receiver mounted in and confined-- substantially within the. header space defined by said roof and ceiling lining, means arranged to hold saidreceiver within said header space, a low capacity antenna mounted abovethe header space for the reception of high frequency signals, 'a short leadin or low capacity having a length :below said ,roof less than the distance between said .roof and ceiling lining and conectin the antenna to the receiver, variable'inductance tuning means in the header space arranged for tunin the antenna, said radio receiver and antenna leadin being so disposed in;close proximity to said roof that said roof-serves as an electro-static shield for the radio receiver and antenna leadin and means are remote point in the automobile.
12. In a'radio receiving system, in an automoreceiver mounted/in and confined substantially within the header space defined by said roof and ceiling lining, means arranged to hold said receiver within said header-space, a low capacity 7 antenna mounted above the header space for th jrangedfor actuating the tuning means from a receiver and antenna leadin being so disposed in close proximity to said roof that said roof serves as an electro-static shield for: the radio receiver and. antenna leadin and means including a, footswitch operable by the driver of the automobile and arranged for actuating the inductancetuningmeans. l
the header space, a leadin of low capacity having a length below ,saidroof less than the distance between said roof and ceiling liningand connecting said receiver to said antenna, and means arranged on the floorboard for controlling the volume of signals reproduced by said receiver.
14. In a radio receiving system in'an automobile having a header space defined by the roof and ceiling lining of the automobile, a complete radio receiver including. an inductance tuning unit mounted substantially within the header space, a low capacity antenna operatively connected to said receiver andarranged to betuned by saidinductance unit, means arranged to hold said receiver within-said headerspace, a leadin of low capacity having a length below said roof less than the distance between said roof and ceiling lining and'connecting said antennato said receiver, means arranged :for actuating said unit from a remote point in the automobile, andadditional meansarranged for controlling th -.volum'e output of signals reproduced-by the receiver from said remote point. r i
15. In a radioreceiving system in an automobile having a header sepace defined by the roof and ceiling lining of the automobile, a complete radio receiver mounted substantially in the header space, means arranged to'hold said receiver within said header space, a low capacity antenna mounted above said header space, a leadin of low capacityrhaving a length below said roof less than the distance. between said roof and ceiling lining and connecting said antenna to said receiver, means operable by the foot of the automobile driver for controlling the volume of output of said radio receiver, means operable at the, header means arranged to hold said receiver within said 3 header space, an antenna mounted above the header space and arranged for thereceptlon of high frequency signals, and arranged for. the
transfer of energy therebetween, a short. leadin of low capacity having a length below saidroof less. than the distance between said roof and celling lining and connecting 'theante'nna to the receiver, variable tuning means located in the header space and arranged for tuning the antenna, means arranged for controlling the volume of said receiver, means arranged for muting said receiver, and means including a single operating member movable to actuate said tuning means, muting means and volume control means.
17. In combination, a radio receiver mounted substantially in the header space of a vehicle between its roof and ceiling lining, a metal box en-' closing high frequency elements of the radio re-' ceiver, said metal box being so disposed in re: lation to said roof that said roof additionally shields the high frequency elements, an antenna mounted above said roof and insulated therefrom, and a leadin of low capacity having a length below said roof less than the distance between said roof and ceiling and connecting said antenna to said high frequency elements.
18. In combination, radio frequency apparatus mounted in the header space of a vehicle sub-- stantially between its roof and ceiling, means ar ranged to hold said radio frequency apparatus substantially within said header space, an antenna mounted substantially above the roof of said vehicle adjacent said header space, and a leadin having a length below said roof not substantially greater than the distance between said roof and ceiling lining and connecting said antenna to said radio apparatus.
19. In combination, a radio tuning unit comprising a tuned circuit including a tuning element mounted in the header space of a vehicle is between its roof and ceiling lining, means arranged to hold said tuning unit substantially within said header space, an antenna mounted substantially above the roof of said vehicle adjacent said header space, and a leadin of low capacity having a length below said roof not sub stantially greater than the distance between said roof and ceiling lining and connecting said antennato said tuning unit, said tuning element having an impedance over its tuning range conjugate to the impedance of said antenna over the same tuning range.
GILBERT E. GUSTAFSON.