US1941543A - High frequency radio signaling apparatus - Google Patents

Description

2 Sheets-Sheet l O. S. PUCKLE Filed July 14, 1932 HIGH FREQUENCY RADIO SIGNALING APPARATUS Jan. 2, 1934' Jan. 2, 1934. o. s. PUCKLE 1,941,543 HIGH FREQUENCY RADIO SIGNALING APPARATUS 2 Filed July 14, 1932 2 Sheets-Sheet 2 WWMWWWWW ..L- 1 Z I INVENTOR 01751 5721/10/06? Pl/C/(Z ATTORNEY I Patented Jan. 2, 1934 UNITED STATES PATENT OFFICE HIGH FREQUENCY RADIO SIGNALING APPARATUS Application July 14, 1932, Serial No. 622,475, and

' Great Britain July 27, 1931 10 Claims.

This invention relates to high frequency transmitters and receivers, and more particularly to ultra short wave radio transmitters and receivers. I

In short wave radio transmitters and receivers, it is common practice at the present time to insert choke coils in the energy leads, e. g. from batteries, to the various points of a transmitter or receiver to which energy must be fed, these chokes being provided for the purpose of preventing dissipation of radio frequency energy through and from the energy supply circuits. Such chokes, which ofier very high impedance to the radio frequency energy, but allow direct currents or low frequency currents to pass practically without obstruction, are commonly provided in the filament circuits and in the voltage supply leads to the anodes and grids of the valves in radio apparatus. Where, however, ultra short wave work is in question i. e. where the working frequency corresponds to a wave length of about 5 or 6 meters or less, and especially where the working wave length is below 3 meters, considerable diiiiculty is experienced in designing and more particularly in testing chokes suitable for thepurpose in question.

The present invention has for its object to provide an easily manufactured and tested substitute for chokes for use for the purposes above referred to.

According to' the present invention, instead of using chokes in the manner above indicated, there are employed in substitution for said chokes, lengths of two conductor line, such lengths being each approximately one-quarter of the working wave length or approximately an odd number of quarter wave lengths long and each length of two conductor line is .bridged at or near the end desired, to be of substantially zero potential at the high frequency by a small terminating load impedance in shunt across the two conductors thereof.

Preferably the two conductor lines consist of lengths of concentric feeder, the outer tube or conductor of which is maintained substantially at earth potential from the point of view of the supply voltage, and the terminating impedance consists of condensers of small impedance.

A two conductor line which is exactly onequarter wave length long and is terminated by a load has an input impedance equal to the square of the characteristic impedance divided by the terminating or load impedance. Therefore, by making theload impedance small or the characteristic impedance large, the input impedance concentric rod or tube, the characteristic impedo ance is given by the formula:

Z,,=138 log 10 2-:

where Rz'is the radius of the outer tube and R1 the radius of the inner tube or rod. Therefore, by altering the radius of the outer and/or of the inner conductor, the characteristic impedance may be varied over a wide range.

It will, of course, be appreciated that owing to the presence of the circuits connected to a two conductor line employed in carrying out the present invention, the said line will not in every case be exactly a quarter of a wave length or an odd plurality of quarter wave lengths long, and it is for this reason that the term approximately" an odd number of quarter wave lengths long, has been employed in defining the present invention.

Preferablywhere a concentric feeder construction of two conductor line is employed the said concentric feeder is telescopically arranged so that its effective length may conveniently be adjusted. If desired also, means may be provided for varying the position of the terminating load with respect to the conductors of the two conductor line. Where the two conductor line is constituted simply by parallel .wires, the terminating load may conveniently be carried by a simple insulating bridge bridging the two wires so that the two terminals of the load are in contact therewith, the bridge being arranged to be movable along the two wires. Where, however, a length of concentric feeder is employed, it is more convenient in practice to arrange the outer conductor in two parts'sothat it is telescopic. It will be understood. of course, that from the theoretical point of view, adjusting the length of a two conductor line, for example by employing a telescopic concentric feeder, and adjusting the position of the terminating load are equivalents .of one another and either or both expedients may be employed as desired.

It is permissible for the conductors of a'two conductor line to extend beyond the point at which the terminating load is connected, but it is desirable that the amount of such extension iild not exceed one quarter wave length. For

xample, where the two conductor line is constituted by parallel wires, these wires may extend beyond the bridge carrying the terminating load, while, where a length of concentric feeder is employed, it is convenient to utilize a fixed inner conductor and a telescopic outer conductor and to carry the terminating load from inner or outer of the two portionswhich together constitute the telescopic outer conductor. For example, in one such construction wherein the terminating load is constituted by a condenser (this construction being suitable for use on very short wave lengths) one electrode of the terminating load condenser is constituted simply by a small copper or brass tube carried by a disc or spider attached to the telescopic outer conductor, the other electrode .being the inner conductor. This construction offers the advantage that, except for the contact between those parts of the outer tube which telescope into one another, there are no moving contacts. As regards this contact between the two portions of the conductor which telescope into one another, it is preferable to make the inner of the two telescoping portions of thin material (usually copper) so that the change of impedance at the junction between the telescoping parts is kept as low as possible.

The invention is illustrated in and further explained with reference to the accompanying drawings.

Referring to Figure 1 which shows the invention as applied to a filament supply system, one terminal of the battery or other source 1 is connected to the central conductor 2 of a concentric feeder 23, one-quarter of a wave length long, and the other is connected to the outer conductor 3, the two conductors 2 and 3 being bridged at the other end by the filament 4 of the valve 6. The battery end of the feeder 2, 3, is also bridged as shown at the appropriate length by a small load condenser 5 or other suitable load impedance.

Similarly, in the case of an anode supply system, illustrated in Figure 2, the concentric feeder 2, 3, is bridged atone end by the anode cathode space 4-7 of the valve 6 to be supplied with energy, and at the other by a shunt condenser 5 and in parallel therewith a loop circuit consisting, for example, of the primary 8 of an output transformer 9 and the source 10 of anode potential in series. A radio frequency by-pass condenser, not shown, may in certain cases be connected as in the usual way between the anode and filament of the valve 6.

Figure 2a represents the arrangement of Figure 2 schematically redrawn to show the voltage distribution, the said distribution being represented as in the usual conventional manner by means of the broken line X. Figure 2b corresponds also to Figure 2, but shows the current distribution, the said distribution being represented as in the usual conventional manner by the broken line Y. The impedance at that end of the concentric conductor indicated by an arrow head in Figures 2a and 2b may readily be made very large and indeed to approximate to infinity.

A form of concentric feeder suitable for use in carrying out the present invention is illustrated in sectional elevation in Figure 3 in which, as will be seen, the outer conductor consists Tof two parts 3a and 3b which can telescope into one another. Figure 4 shows in sectional elevation and Figure 5 in sectional end view, a preferred construction wherein the terminating load impedance is a condenser, this condenser being constituted by the central conductor 2 and a tube 5' said conductor and carried by means of a spider'fi from the part 3a, or the part 3b as may be desired, of the outer conductor.

The use of telescopic or otherwise adjustable two conductor lines presents, of course, the further advantage of adaptability for efficient use in receivers which may be desired to operate at any of a plurality of different wave lengths.

If desired, where telescopic or other adjustable two conductor lines are employed, a scale and indicator may be associated with the adjustable line, the scale being marked in wave lengths so as to indicate the correct adjustment of the length of the line for the different wave lengths marked on the scale, and an insulated handle may be fittedefor control or adjtwtment purposes, e. g. when the apparatus is incorporated in a radio receiver.

The present invention plicable to push pull and similar symmetrical circuits. Fig. 6 illustrates such an application. In this circuit the use of two separate two conductor lines (for example, for use in connection with feeding anode potential to the two push pull connected valves) may in some cases be dispensed with and the two lines be combined in a three conductor arrangement, one conductor being electrically and mechanically common to both halves of the push pull or other symmetrical is, of course, also apcircuit. In Fig. 6, where parallel wires are employed to constitute the two conductor lines the anode feed arrangementfor the pair of valves 15 and 16 in push pull includes, instead of two separate two conductor lines, an arrangement consisting of three conductors, 12, 13 and 14 the central conductor 13 being common to both halves of the push pull circuit and being maintained at substantially earth potential from the radio frequency point of view.

In carrying the present invention into practice the smallest possible number of supports or dis tance pieces should be used for locating theparallel wires or other conductors of a two wire line or concentric feeder and such supports or dis+ tance pieces as are employed should, of course, be of good radio frequency insulating properties and low dielectric loss.

It will be seen that the ,present invention is quite practicable and convenient and that the device employed in substitution for ordinary chokes is not unduly cumbersome since, in the case of a working frequency equivalent to a wave length of 3 meters, the total length of a device in accordance with this invention would be under 30". If desired, of course, a device in accordance with this invention may be folded.

Although the invention is of general applicaployed in receivers working on wavelengths of one meter or less, and in circuit'arrang'ements operating on the so-called Barkhauseni-Kurz principle or similar principle depending upon electronvelocity.

It is to be understood that it is intended to an Odd multiple of a tion, it is, however, very advantageously emtending from said source to the electrode adapted to be energized, said concentric line comprising an outer conducting tube and an inner conductor insulatingly spaced from the walls of said tube and substantially in the center thereof.

2. Apparatus as defined in claim 1 includin "a small load impedance connected across said two conductors of said line at the end nearest the source of potential.

3. High frequency apparatus having, in combination, an electron discharge device comprising a plurality of electrodes, a source of potential for energizing one of said electrodes, a concentric two conductor line extending from said source to the electrode adapted to be energized, said concentric line comprising an outer conducting telescopic tube and an inner conductor spaced from the walls of said tube and substantially in the center thereof, and a condenser arrangement having a small load impedance across said inner and outer conductors.

4. In high frequency apparatus employing an electron discharge device having a plurality of electrodes and a source of potential for energizing one of said electrodes, means for preventing the working frequency from reaching said source comprising a two conductor line approximately an odd multiple of a quarter wave length long extending from said source to the electrode adapted to be energized, said line being bridged by a terminating load of small impedance in shunt across the two conductors of said line.

5. In high frequency apparatus employing an electron discharge device having a plurality of electrodes and a source of potential for energizing one of said electrodes, means for preventing the working frequency from reaching said source comprising a two conductor line approximately an odd multiple of a quarter wave length long, said line being bridged near one end thereof by a terminating load of small impedance in shunt across the two conductors of said line.

6. In high frequency apparatus employing an electron discharge device having a plurality of electrodes and a source of potential for energizing one of said electrodes, means for preventing the working frequency from reaching said source comprising an adjustable two conductor line approximately an odd multiple of a quarter wave length long extending from said source to the electrode adapted to be energized, said line being bridged near one end thereof by a terminating load of small impedance in shunt across the two conductors of said line.

7. In high frequency apparatus employing an electron discharge device having a plurality of electrodes and a source of potential for energizing one of said electrodes, means for preventing the working frequency from reaching said source comprising a pair of parallel conductors approximately an odd multiple of a quarter wave length long, said conductors being bridged near the end desired to be of substantially zero potential at the working frequency by a small terminating load impedance in shunt across the two wires.

8. High frequency apparatus having, in combination, an electron discharge device comprising a plurality of electrodes, a source of potential for energizing one of said electrodes, a concentric two conductor line approximately equal to an odd multiple of a quarter wave length long extending from said source to the electrode to be energized,

said concentric line comprising an outer tube and an inner conductor spaced from the walls of said tube and substantially in the center thereof, and

a terminating load of small impedance in shunt across the two conductors of said line, said impedance being constituted by a metallic electrode which is carried by the outer conductor of said line and which is in electrostatic association with the inner conductor.

9. High frequency apparatus as defined in claim 8 characterized in this, that said electrode carried by the outer conductor is a tube surrounding the inner conductor.

10. High frequency apparatus having, in combination, two electron discharge devices in pushpull relationship each having anode and cathode electrodes, said anodes being connected together and said cathodes being connected together, a source of potential for said anodes connected between said anodes and cathodes, a three conductor line comprising an inner and two outer conductors, said conductors being parallel for a distance approximately equal to an odd multiple of a quarter wave length, said inner conductor extending between said cathodes and one side of

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