US2032782A - Receiver of high frequency electrical energy - Google Patents

Description

March 3, 1936.. s. Y. WHITE 2,032,782 E RECEIVER OF HIGH FREQUENCY ELECTRICAL ENERGY Filed April 18, 1925 2 Sheets-Sheet l March 3, I936.

5. Y. WHITE 2,32,782

RECEIVER OF HIGH FREQUENCY ELECTRICAL ENERGY '7 Filed April 18, 1925 2 Sheets-Sheet 2 Q *W I M W w, z:

Patented Mar. 3, 1936 UNITED STATES PATENT OFFICE RECEIVER OF HIGH FREQUENCY ELECTRICAL ENERGY America, New York, Delaware Application April 18,

2 Claims.

While my invention relates generally to receivers of high frequency electrical energy, it has for a particular object the reception of radio signals, particularly those originating as high or radio frequency carrier waves modulated at lower or audio frequency to represent signals or telephonic tones.

An object of my invention is to provide a receiving system that will not radiate high frew quency energy to any substantial degree even though powerful high frequency currents be acciden't'ally or deliberately created in the receiving system.

Another object of my system is to permit the free use of regenerative or feed back amplifying or oscillation generating circuits without emitting disturbing high frequency energy from the antenna or collector.

A further object is the provision of a receiver 5.) whose antenna or collector maybe closely associated with the antennae or collectors of other receivers without being influencedby the tuning of such receivers or exerting any tuning influences on them. {3 An additional object is to provide a receiving system in which the tuning portion is substantially electrically independent of the collecting or absorption portion to the end that the tunable circuits may be calibrated in the factory, and the receiver thereafter used with antennae of different physical proportionsor electrical characteristics without nullifying the calibration.

Still another object is the provision of a reoil a complicated tuning system and the usual plurality of tuning controls.

A still further object is the provision of. a receiver that is simple, requiring simple and inexpensive alterations in present day receivers to obtain the objects and advantages heretofore set forth.

Other objects and advantages will be readily appreciated by those skilled in the art by reference to the figures of the accompanying drawings and the description of my invention.

In present day practice it is usual to divide a receiver into two portions, one a tuned high frequency portion in which the high frequency energy is first received, and where it may or may not be amplified; and two, a low frequency portion in which the low frequency currents resulting from detection of the high frequency energy are amplified in one or more stages before delivery to the telephones, loud speaker or other transceiver that is selective and yet avoids the use of N. Y., a corporation of 1925, Serial No. 24,088

lating device. The antenna or collector which delivers the high frequency energy to the tuned high frequency portion is quite commonly tuned to the frequency of the high frequency energy, or at least is a high frequency circuit, and therefore is a good radiator of any high frequency energy which may be accidentally or deliberately generated in the tuned high frequency portion of the receiver. This fact has made the very efficient regenerative or feed back type of receiver undesirable in spite of its eificiency in the present extensive use of radio recivers, involving as it does the employment of hundreds of collectors in very small areas in thickly populated sections of the country. It is also well recognized that where antennae or collectors are closely associated and are tuned, or are high frequency circuits associated with tunable high frequency circuits in the receiver, there results tuning reactions from one system to another as the tuning controls are operated that is very annoying and often destructive of good results. These radiative and reactive tuning difiiculties were well appreciated before the present popular use of radio in commercial and shipboard installations where effort was made to operate a number of receivers simultaneously.

My invention avoids these difficulties by connecting the antenna to the low frequency amplifying portion of the receiver to first deliver the high frequency energy to this portion, passing the high frequency through the low frequency amplifying portion (through at least one stage if it is a multiple-stage amplifier), arranging for the high frequency portion to extract its energy sec- 0nd hand from the low frequency portion, and after amplification (if. such is had in the high frequency portion) and detection of the high frequency energy, delivering the resulting low frequency currents to the low frequency amplifying portion irrespective of the high frequency energy which enters this portion.

My invention will be best understood by reference to the figures of the accompanying drawings, illustrating in particular its use in connection with the reception of radio signals in a few of the circuit arrangements well known to the art.

Fig. 1 illustrates my invention used in a simple form of circuit containing a regenerative type of amplifier detector and one stage of audio frequency amplification.

Fig. 2 illustrates my invention used in a receiving system having one stage of radio. frequency amplification, a detector and two stages of audio frequency amplification.

' erably variable, to the input circuit.

Fig. 3 illustrates my invention used in a receiving system having a regenerative type of amplifier-detector, and two stages of audio frequency amplification.

Like reference characters represent like parts as far as possible throughout the figures.

Referring to Fig. 1, VT1 is a three electrode vacuum tube having a tunable high frequency circuit comprising inductance L1 and variable capacity 01 included in its input circuit. The vacuum tube is connected to regeneratively amplify high frequency currents through having the inductance L2 in its output circuit coupled, pref- The tube is also connected for detection of modulated high frequency currents through having the wellknown grid leak-stopping condenser combination GL in circuit with the grid of the tube, and the grid connected to the positive side of the filament. The output circuit of tube VT1 includes the primary winding P1, of an audio frequency transformer T1, and the primary may be shunted by a capacity C2 if the Winding P1 has not suffici'ent distributed capacity to by-pass the high frequency currents. The secondary winding S1 of the transformer T1 is included in the input circuit of the vacuum tube VTz, which tube is connected for amplifying through having its grid connected to the negative side of the filament and through having a suitably high source of potential in the output circuit. The output circuit of VT2 includes the high frequency winding L3 coupled to the inductance L1 in the input circuit of VT1, and may for instance be a comparatively few turns of wire wound on the same form as the inductive winding L1; or the plate circuit may be coupled to the input circuit of VT1 in any manner suitable for transferring high frequency energy thereto, as for instance the capacity coupling I will describe in connection with my other figures. The output circuit of VTz includes a loud speaker LS, telephones, or other suitable translating device, shunted if desirable by a high frequency by-pass condenser C3. A is a battery or other source of energy for heating the filaments of VTI and VT2, R1 and R2 are rheostats for controlling the extent of heating of the filaments, and B is a battery or other source of energy for energizing the output circuits of VTl and VT2, suitable operative polarities being as indicated. H is an antenna or other suitable collector of high frequency energy connected to one terminal of the secondary winding S1, and may include a relatively small capacity in series therewith as indicated by the condenser C4 shunted by the switch S. The other terminal of secondary S1 may be connected to a suitable ground G, or the ground connection may be omitted if there is suflicient capacity to ground in the batteries and other elements of the receiver.

The operation and results may be accounted for as follows: The impedance of the audio frequency transformer secondary S1 is the principal impedance in the collector circuit to the flow of high frequency currents, and being a high impedance to the flow of such currents there results a substantial counter electromotive force developed across its terminals, and therefore across the grid and filament of the vacuum tube VT1, even though the collector circuit currents are very small due to an entire absence of resonance, as is necessarily the case where a high frequency current carrying circuit includes a winding of impedance suitable for audio frequency currents.

Since the amplitudes of the high frequency variations in the output current of the three electrode vacuum tube depend upon the degree of potential variations on the grid of the tube and its amplifying ability there results, in view of the tube being suitably connected for amplifying, a very strong reproduction of the incoming high frequency signals in the output circuit for delivery to the input circuit of the high frequency portion of the system through the coils L3 and L1, and my experiments have shown that with my system stronger currents are delivered to the high frequency portion of the system than in the usual system where the signal is collected on a more or less tuned antenna and delivered directly to the high frequency portion. In other words, what I lose in not using resonance in collection of signal ismore than regained by utilizing an amplifier capable of the double function of high and low frequency amplification, but which without my invention is only utilized for the single function of low frequency amplification.

acts as any ordinary regenerative amplifier-detector and single stage audio frequency amplifierf Once the amplified signal energy is delivered. to the high frequency portion the system then iii) elimination of radiation from the collector of any high frequency energy that may be accidentally or deliberately generated in the high frequency portion of the system as is too often the case when using the regenerative type'of. receiver I have illustrated, though the well known nuisance occurs in types of receivers that do not include a specific regenerative or feed-back connection- The result is accomplished through the double protection afforded by the stage of audio frequency amplification interposed between the collector and the high frequency portion, and having the collector entirely out of resonance with high frequency currents, and it will be seen that I accomplish this result without the addition of any apparatus, such as is required in the socalled coupling tube system for the same purpose which amounts to an extra vacuum tube interposed between the collector and the part of the system likely to generate high frequency energy, and which is not entirely effective as the collector is a high frequency circuit and does absorb a substantial amount of high frequency energy for radiation in such a system.

For the same reason that my system eliminates radiation it prevents tuning reactions between receivers connected to closely associated collectors, and will even permit connecting a number of receivers to the same collector without such reactions. It is readily apparent that any variations in the isolated electrical constants L1 and. C1, which are the only elements that need be varied for tuning, will not affect the collector H, and therefore any other receiver connected to H or a collector closely associated with H. Conversely, any change in the collector H will not influence the tuning performed by L1 and C1 to any troublesome extent.

My system also permits of extreme selectivity or sharp tuning with a simplicity heretofore unknown to the art. It will be noted that the usual tuning devices included in the antenna or collector of the ordinary system are entirely done away with, leaving the variable condenser C1 in the input circuit of VT1 as the only device to be operated for tuning. Since the input circuit derives its energy from the output circuit of VTz, which is a very high impedance circuit, including as it does the space path of the tube, and there is loose coupling between the circuits due to the comparatively small number of primary turns L3 previously referred to, the mutual reactions between the two circuits are small, the tunable circuit L1 C1 is practically uninfluenced and, therefore, sharply a one-frequency circuit.

A further advantage is that tuning is independent of the collector sothat the tunable circult may be carefully calibrated by the manufacturer for different wave lengths (frequencies) and the calibration will hold good no matter how or where the receiver is used.

The purpose of the condenser C4 if used is to insert a high reactance in the collector circuit to the flow of low frequency currents, as may tend to occur if the collector is located near a lighting or other transmission line carrying sixty cycle or other low frequency currents. A condenser of capacity sufficiently low to be very effective against such low frequency currents will practically uninfluence currents of the high frequencies in common use.

Fig. 2 illustrates a receiver having a low frequency portion comprising two stages of audio frequency amplification including the vacuum tubes VT1 and VT2, and a high frequency portion including the vacuum tube amplifier VT1 and the detector D, which may be a crystal, vacuum tube or other suitable detector. In this figure the high frequency currents are collected by H, transferred by the secondary S1, of the low frequency transformer T1 tothe vacuum tube VTz where they are amplified and then forced from the plate circuit by a high frequency choke L5 through a coupling condenser C5, (which may be made variable) to the high frequency portion, and there selectively received by the tunable circuit comprising inductance L1 and variable capacity C1, then amplified in VTl and selectively transferred to the detector D through inductance La and L6 and variable capacity Cs. Following detection by detector D, the low frequency currents pass through transformers T1 and T2, being amplified by vacuum tubes VTz and VT3, to the translating device LS. As before, the high frequency portion is isolated from the collector which is not tuned to a high frequency and for this reason as before pointed out in connection with Fig. 1, the multiple high frequency tunable circuits of Fig. 2 may be calibrated with precision in the factory for various well-known purposes with assurance that the isolating tube and untuned antenna will insure maintaining the calibrated status of the tunable circuits under different conditions of use of the receiver.

Fig. 3 is like Fig. 1, except there are two stages of audio frequency amplification including the vacuum tubes VT2 and VTs, and the high frequency currents collected by the antenna H pass through both stages before going to the high frequency portion, the transfer of high frequency currents from the first audio stage to the second audio stage being facilitated by the radio frequency transformer RF. The high frequency coupling between the audio frequency portion and the high frequency portion is shown as a capacity coupling including the condenser C5 and the choke coil L5, though the choke coil may be omitted and the winding of the telephone LS or other translating device used as such choke, in which case it would preferably not be shunted by the high frequency current by-pass condenser C3. The high frequency currents delivered to the high frequency portion are then handled as explained in connection with Fig. 1. Another arrangement is shown for preventing low frequency currents collected by the antenna H from affecting the low frequency amplifying system consisting of the condenser C4 in series with the transformer secondary S1, and a high frequency choke L4 shunting the condenser and transformer secondary. Low frequency currents flow easily through the choke and are stopped 1."

by the condenser 05, and therefore do not affect vacuum tube VT2.

Many other combinations of my system with well known circuits may be readily made, but

these are immediately obvious to those skilled in t the art from the foregoing description and are here omitted for brevity, though I do not wish to have my invention limited to the particular circuits shown by reason of failure to show obvi ous combinations with other circuits.

Having fully described my invention, I claim:

1. In a system for receiving high frequency electrical signals modulated at an audio frequency including a high frequency portion and a low frequency portion comprising a vacuum tube having a cathode and control grid, an antenna for collecting said signals, a coil connected between said grid and cathode and serving to transfer said signals to said low frequency portion and a condenser having one side connected to a said grid and its other side to said antenna, the capacity of said condenser being so small as to substantially prevent the transfer of undesired currents of low audio frequency picked up by said antenna to said control grid.

2. The combination defined in the preceding claim in which an inductance having a high impedance to the signal frequency and a low impedance to audio frequencies is shunted across the series connection of said coil and condenser.

SIDNEY Y. WHITE.

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