US2026661A - Tuning means - Google Patents

Description

Jan. 7, 1936.

5. TREVOR TUNING MEANS 2 Sheets-Sheet 1 Filed April 30, 1932 INVENTOR Y. BERTRAM TREVOR BY #W ATTORNEY Jan. 7, 1936.

B. TREVOR TUNING MEANS Filed April 50, 1932 2 Sheets-$heet 2 INVENTOR BERTRAM TREVOR BY M ATTORNEY Patented Jan. 7, 1936 UNITED STATES TUNING BIEANS Bertram Trevor, Riverhead, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application April 30, 1932, Serial No. 608,350

9 Claims. (01. 25o-2o) This invention relates to radio signalling systems and more in particular to systems having means for rendering them operative over a wide range of frequencies.

Radio signalling systems for operating over a wide range of frequencies have been known heretofore in the art. For example, 'Brown, United States Patent No. 1,677,268, shows such a system and in particular a receiver to be used in such a signalling system. In this receiver to cover a broad band of frequencies plug-in coils are used to interconnect the thermionic amplifiers and to connect the antenna system with the first amplifier. Such an arrangement makes possible the use of two or more sets of tuning coils to be used with a ganged condenser in a radio receiver. When it is desired to change the frequency band over which the receiver may be tuned all that is necessary is to plug in a new set of coupling inductances.

In arrangements known heretofore of this type considerable difliculty has been encountered in that the inductances for interconnecting the circuits are initially made of like electrical characteristics but when inserted in the receiver and/or in the shielding compartment the reflected capacity between the coils and adjacent shielded surfaces changes the effective capacity of the several inductances so that when they are connected with a uni-control ganged condenser, each unit of which is of like capacity, the several coupling inductances are not all tuned to resonance for any given setting of the condenser control means.

The above disadvantages have been corrected by the use of equalizing capacities connected in parallel with the main tuning capacities. These equalizing capacities are adjusted to make the total tuning capacity of each circuit the same at any main condenser setting. Such an arrangement gives perfect gauging. Such an arrangement, however, is only possible where a single set of tuning coils is to be used.with the ganged condenser. This ideal condition becomes upset in many instances where several sets of coils are to be used with the same tuning condenser and the accompanying equalizing condensers, because of a possible change in the reflected capacity into one or more of the tuned circuits. In particular, the tickler coil of the detector in a receiver of this type couples with the detector tuning inductance or coupling inductance a relatively larger capacity in circuits over certain wave hands when operating at high frequencies. An antenna coupling coil could also be another source of reflecting capacity which might produce different effects on the various coupling inductances.

All of the above disadvantages are overcome in the present invention by the use of several sets of coupling inductances, each inductance of which is enclosed in a separate metallic shield, and each inductance of which is supplied with a separate equalizing condenser connected in parallel therewith. With such an arrangement 10 it is possible to make every coil set gang together properly. The ganged condensers with their added wiring and fixed equalized capacities must be equalized over the tuning range with no coils connected therein. Each coil set is then equal- 5 ized with its own set of equalizing condensers as it is connected or plugged in to give proper ganging without disturbing the equalization of the receiver when the coils are not in place.

The novel features of my invention have been set forth more particularly in the claims appended hereto.

The nature of my invention and the operation thereof will be understood from the following detailed description and therefrom when read in connection with the drawings throughout which like reference characters indicate like parts and in which: l

Figure 1 shows and illustrates the inductance system of the present invention, Figure 2 shows one of the inductance units of Fig. 1 incorporated in a thermionic receiver.

Referring to the drawings, and in particular to Fig. 1 thereof, S is a shield having several compartments l in each of which is enclosed one of the several ganged, tuning capacities C. As shown, each. of these capacities has one armature connected to the shield S which may be grounded, and the other armature with a male contact K, the purpose. of which will appear more in detail hereinafter. In order that the tuning capacity of all of the capacities C may be made equal,

equalizing capacities C1 are connected in parallel with each of the main capacities C, as shown. All of the capacities C may be adjustedby means of a single control 4, as indicated. This unit just described is integral with the receiver proper.

In order to tune the receiver over a wide frequency range each receiver is supplied with a plurality of units each comprising a plurality of tuning inductances L enclosed, as shown in separate compartments 2 in a removable coil box B. The first of these inductances L is in the arrangement shown adapted to be coupled with a source of high frequency energy, as, for'example, an antenna system by means of a coupling inductance L1 coupled through an electrostatic screen 6 to the inductance L. The last inductance L in this system is coupled conductively and inductively with an inductance L3 by means of which energy may be fed back from the output of a thermionic detector to the inductance L of this unit. Each inductance L has a female contact 8 connected to one terminal, as shown. The contacts 8 are located adjacent openings 9 with insulating members I!) to permit contacts K to enter the shield B and close the circuit between each inductance L and its tuning capacity C when the removable coil box B is placed in position on the compartment S for the tuning condensers. The other terminal of each inductance L, except the last, is connected as shown at H to the shield B. The tickler coil L3 associated with the final inductance L also has one terminal connected at l I, as shown, to the shielded coil box B and the other terminal connected with a contact I2 cooperating with a contact I 4 which completes a circuit to the detector plate when the removable coil box B is placed in position on the unit S enclosing the ganged condenser.

As pointed out briefly above, the efiective capacity of each main tuning capacity C can be made equal by means of its associated equalizing capacity C1. This results that in each position of the control for the ganged condenser, the effective capacity of each condenser is the same. However, the receiver might not be tuned to resonance in each circuit over the several frequency bands since, as pointed out above, each different set of plug-in inductances L might have different reflected capacity and result in different total tuning effect for each inductance unit. This is corrected in accordance with the present invention by providing for each inductance L a separate equalizing capacity C3. In practice, each inductance in each set of tuning inductances L, is tuned by means of its equalizing condenser C3 so that the effective inductance and capacity of all of the inductances are the same over their tuning range irrespective of the amount of refiected energy into the detector tuning unit by the tickler coil and/or the capacity reflected into the inductance due to the antenna coupling coil.

In operation, when it is desired to change the frequency over which the receiver is to be tuned all that is necessary is to position on top of the ganged condenser compartment or shield S the removable coil box B which contains the inductances. This is accomplished by merely plugging the coil box B into the condenser unit. When in position the contacts K of the shield S are inserted into the contacts 8 of the box B. The insulating members I i) prevent contact between the contact members K and the metallic shield B.

The equalized inductance systems in the removable coil boxes and the balanced tuning capacities C and C1 in the unit S may be utilized to connect or couple together thermionic tubes for relaying or amplifying radio signals. Any type of coupling may be used. For example, the inductances in the individual containers may be the windings of transformers, which may be arranged to couple in cascade the thermionic tubes, or they may be coupling inductances which cooperate with capacities to couple the thermionic tubes in cascade by what is known as inductive and capacitive coupling. The inductance system is not limited to these two types of coupling since, obviously, any combination of the above types of coupling may be used since the inductance systems of the present invention will obviously adapt itself to any type of coupling known in the art today.

In Figure 2 has been shown an arrangement in 5 which a plurality of thermionic amplifiers or repeaters are coupled by means of the novel inductance system disclosed in Figure 1. The inductances L, the equalizing condensers C3, and the main tuning capacities C, which are ganged, and 10 the balancing capacities C1 are shown as being included in a single box or container BS. Actually, as indicated above in conection with Figure 1, the' inductances and equalizing condensers are in a separate container which can be replaced with 15 another system covering a diflerent range by merely removing the container from the unit S. The input electrodes of tube I 6 are connected with one of the inductances L and its associated equalizing condenser C3 and main condenser C to 20 tune the input circuit of the thermionic tube Ill to the desired frequency. The condenser C5 serves as a coupling circuit filter condenser. Another inductance L and its cooperating equalizing condenser C3 and main tuning condenser C and its 25 trimmer C1 is interposed between the source of oscillations or antenna inductance L1 and the inductance system LC connected in the input circuit of tube it. In this manner a highly descriminating or selective circuit is interposed between the input 30 of the first thermionic amplifier and the signal source L1. IThis insures that only the desired signal potentials are impressed upon the input electrodes of the tube Hi.

The repeated signal oscillations appearing on 85 the output electrodes of tube It are forced by inductances I through coupling capacities C6 on to another of the inductance system L, C3, from which they are transferred to a second'inductance A system L, C3, and to the input electrodes of the 40 tube l8. These two inductance systems L, C3, interposed between the output of thermionic tube l6, and the input electrodes of thermionic tube [2, further insure selective descrimination between the desired signals and any undesired signals. In other words, a receiver coupled as indicated here responds only to the frequency to which the several inductance systems therein are tuned. The output circuit of tube I 8 is coupled by a single inductance system L and choking inductances I and coupling condenser C6 to the input electrodes of a third thermionic amplifier 20, which is in like maner coupled to the input electrodes of a detector 22 and in which the signals are demodulated and may be utilized from the output circuit thereof in any known manner.

Regenerative action in the detector 22 is insured by coupling the anode thereof through a coupling capacity l5 to the terminal of inductance L3, which is inductively and conductively coupled to the inductance L. Heating current for the filaments of the several tubes is supplied, as indicated, by connecting the terminals AT to the positive terminal of a heating circuit, the negative terminal of which is connected to the shield S and to ground.

Charging potential for the screen grids and anodes is supplied from a source not shown, which has its negative terminal connected to ground and a positive terminal connected to the terminals SG+ and B+.

Biasing potential for the grid electrodes may be supplied from the negative terminal of a biasing source not shown having its positive terminal connected to ground by connecting the C leads to said grids to the negative terminal of said source.

A tuning system, including the equalizing capacities connected inparallel with each of the plug-in inductances, has been used in a short wave receiver in which a 6-gang condenser was used with five separate sets of plug-in coils. Each coil set of six coils was built in one container to be plugged into the receiver as a unit, as hereinbefore described. The receiver is operated very efficiently over a range of from 20,000 to 2500 kilocycles. Although the tuning system has been shown applied to a receiver, it will be understood that it is not limited to such use since it may be used in various manners in signalling. For example, such a tuning unit may be used very efficiently as a band pass pre-selector.

I claim:

1. A radio receiver for receiving signals over a wide band of frequencies comprising a plurality of individually shielded thermionic stages and tuning means interconnecting the stages comprising, a shielded coupling inductance for each stage, an individual equalizing capacity for each inductance and contained within the shield, a shielded tuning unit having separate compartments containing a main tuning capacity for each inductance and an equalizing capacity for each tuning capacity.

2. A radio receiver comprising a plurality of thermionic stages and tuning means connecting each stage comprising, a plurality of individually shielded tuning units each having a plurality of inductance coils each having effective electrical inductance of substantially like value, individual equalizing means contained within the shield for each inductance coil, and means for synchronously tuning said inductances including a shielded unicontrol tuning unit including an individually shielded tuning capacity for each inductance in one of said units and an equalizing capacity contained within the shield for each capacity.

3. A radio receiver comprising a plurality of thermionic tubes, and means for coupling said tubes in cascade and for tuning said receiver over a wide band of frequencies comprising a plurality of separate shielded groups, one of said groups having a plurality of inductance units each unit including a plurality of inductances of substantially like value enclosed in separate shielded conducting chambers, individual tuning means for each inductance contained within the same shielded conducting chamber, a plurality of main tuning condensers with an adjusting condenser enclosed in a main shield member of another group, said main shield member having contacts projecting therefrom and cooperating with sockets in said inductance units to couple the output electrodes of certain ones of said tubes to the input electrodes of a following tube, and to connect the output electrodes of other of said tubes by way of a similar inductive unit to the input electrodes of the following tube.

4. A multi-stage receiver for receiving radio signals over a large band of frequencies, said receiver being divided into two separate groups of shielded compartments, one of said groups forming the main tuning and control portion of the receiver, the other group forming the auxiliary portion of said receiver which comprises a plurality of separate and replaceable shielded plug-in units, each of the said separate replaceable shielded plug-in units to cover the desired band of frequencies and comprising a plurality of tuned circuits within shielded compartments containing coils of substantially the same inductance value, each of the said plug-in units having adjustable capacity means to alter the tuning of said tuned circuits within the shielded compartment, and contact means for each of said shielded compartments to cooperate with corresponding contacts in said main tuning and control portion to place said receiver in effective operation. 10

5. A radio receiver for receiving signals over a wide band of frequencies comprising a plurality of thermionic stages, tuning means for connecting said thermionic stages in a predetermined relation comprising a coupling inductance for each stage, metallic shielding material substantially enclosing each coupling inductance and individual equalizing capacity connected with each inductance, said capacity being contained within the metallic shielded container, a main tuning unit comprising a main tuning capacity for tuning said inductance.

6. A radio receiver for receiving signals over a wide band of frequencies comprising a plurality of thermionic stages, tuning means for connect- 5 ing said thermionic stages in a predetermined relation comprising a coupling inductance for each stage, metallic shielding material substantially enclosing each coupling inductance and individual equalizing capacity connected with each inductance, said capacity being contained within the metallic shielded container, 2. main tuning unit comprising a main tuning capacity for tuning said inductance, and equalizing capacity means connected with each of the tuning 5 capacities.

'7. A radio receiver for receiving signals over a wide band of frequencies comprising a plurality of groups of shielded tuning means, each of said groups comprising a plurality of stages at least 9 one of said groups having individually shielded compartments with an inductance in each stage,

a plurality of contacts which are arranged on the outside of said shielded compartment to contact with at least one or the other groups of said shielded tuning means for the operation of a predetermined band of frequencies within said wide band of frequencies, and individual equalizing capacity shielded with each of the inductances, and contained within the individually shielded compartments, a tuning unit having separate shielded compartments comprising a main tuning capacity for each individual inductance and an equalizing capacity for each stage of said tuning capacity.

8. A radio receiver comprising a plurality of individually shielded thermionic stages and tuning means interposed between adjacent stages comprising, a plurality of tuning units located within a separate individually shielded compartment having a plurality of interstage coupling inductances, individual capacitive tuning means for each coupling inductance and contained within the separate shielded compartment, a shielded uni-control tuning unit having separate compartments containing a tuning capacity for each inductance and a separate equalizing capacity for each tuning capacity.

9. A radio receiver comprising a plurality of thermionic stages and means for tuning said "(0 stages over a wide band of frequencies, said receiver comprising a first and second separate shielded group, the first group comprising a plurality of inductance units'each unit including a plurality of inductances of substantially like value, enclosed within a separate shielded chamber, individual capacitive tuning means for each inductance unit, said inductances and individual capacitive tuning means connected in parallel, a connection from at least one side of the inductance and the individual capacitive tuning means connected to a contact socket which may be plugged into the second one of said separate shielded groups containing a main tuning con- 10 denser comprising, a plurality of condenser units to cover the desired range, said condenser units aving contacts projecting from the shielded group and cooperating with the contact sockets connected to the inductance units to complete the interstage coupling circuits when the circuit of the first shielded group is plugged into the second shielded group containing the plurality of condenser units.

BERTRAM TREVOR.

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