US2144784A - Ultra-short wave high frequency amplifier - Google Patents

Description

Jan. 24, 1939. M. VON ARDENNE ULTRA SHORT WAVE FREQUENCY AMPLIFIER:

Fild Jan. 5, 1935 2 Sheets-Sheet l Jnren/or:

Jan. 24, 1939-. M. VON AR DENNE I ULTRA SHORT WAVEHIGH'FREQUENCY AMPLIFIER Filed Jan. 5, 19:55 2 Shets-Sheet 2 5% in J my 7 0 .0 m an a n /m Jmm se y cc fab. 1 W dfia M 0,

H 11 I in wm wame v r nt 5 Patented Jan. 24, 1939 UNITED STATES PATENT OFFlCE ULTRA-SHORT WAVE HIGH FREQUENCY AMPLIFIER Application January 5, 1933, Serial No. 650,305 In Germany January 14, 1932 8 Claims.

It has not been possible heretofore in ultrashort wave broadcasting systems to supply a large town area on a workable basis with the transmitter outputs which are capable of being produced in practice. Ultra-short receivers with back-coupled audion' are not sufficient. Low reserve of power, earthing difliculties and disturbing polarization effects upon the mounting of the aerials constitute difficulties of a characteristic kind for the receivers. Increase in the output of the transmitter provides merely a gradual improvement. The transmitters would require to be amplified far beyond the present output in order, with the receiving apparatus hitherto employed, to obtain adequate reception. In this manner the transmission would prove very expensive.

The said difficulties are overcome immediately receivers are available having a greater width of band and increased voltage sensitivity. Greater difiiculties exist in the case of ultra-short wave television systems, in which the band modulation to be transmitted is more than 100 times greater than the side band inthe case of ultra-short wave broadcasting systems In order to avoid inadmissible damping of the outer side bands, it is necessary, therefore, to dispense with the use of back-coupling improvement.

The necessity of employing circuits which have not been artificially improved leads to a decrease in the voltage sensitivity of the receiver, which from a practical standpoint cannot be compensated at the sending end by increasing the output.

All of these difliculties may be overcome by the provision of a receiving apparatus which possesses a large width of band with increased voltage sensitivity.

The invention relates to the provision of an aperiodic high frequency amplifier for ultra-short waves possessing the properties referred to, i. e., having with adequate voltage sensitivity a sufficiently large width of band. According to the invention, this is accomplished by the fact that departure is made from the course of pure fullaperiodic resistance amplification, which is capable of being performed only with very high D. C. output, and use made of a so-called semi-aperiodic resistance amplification. This may be accomplished, for example, by the fact that in the anode circuits of the resistance amplifier there are connected oscillating chokes, i. e., chokes which by reason of their natural selfcapacity or by the additional connection of special capacities and attenuation resistances possess a resonance characteristic of considerable band width. This semi-aperiodic coupling is formed according to the usual resistance-capacity coupling, generally called aperiodic coupling. For the normal wave range the use of amplifiers of 7 this kind has little or no importance, as the wave range which requires to be coped with in the ordinary way is much. greater than the band Width of the oscillating choke.

In the ultra-short wave range the condition 10 is different. Due to the characteristic absorption and propagation conditions of ultra-short waves, merely a range enters into the question for the practical use thereof, which is considerably smaller than an octave, viz., the range between m approximately 6.75 and 7.25 m. wave length.

It is possible in this case to perform a valve coupling through the medium of oscillating chokes, i. e., through the medium of self-inductions accompanied by suflicient loss resistance, 20 which resonates at the centre of the wave range, i. e., at approximately 7 m. Wave length, with the valve and connection capacity.

To obtain amplifier units of good efliciency with low consumption of current and a sufficiently wide frequency band for the waverange concerned, it is necessary, in addition to the utilization of a certain resonance effect, to also arrange and assemble the remaining parts and amplifier devices according to certain aspects. In particular it is necessary to reduce at all points the high frequency resistance and all detrimental capacities so far as this is possible. For this reason it is necessary, for example, in addition to the D. C. paths, to provide at all points particularly short, high frequency connections, so that the single leads are freed as far as possible from high frequency. Preferably, therefore, the leading-in points for the wires to the valve electrodes are connected in immediate fashion by condensers with a common point. In addition high frequency chokes must be connected at all points in the leads. Suppression chokes and bridging condensers also require tobe connected in the heating wire.

Particularly important is the use of multi-stage valves, as it is possible only with multi-stage valves of the best construction to maintain the self-capacities Within such limits that with a 7 in. wave band the requisite high voltage sensitivity is obtained. With multi-stage valves constructed with great care it is possible to diminish the capacitative anode loads to such extent that high amplifying figures are capable of being obtained.

The employment of screening grid systems is useful in order to avoid to a large extent the anode reactions, which naturally at these frequencies occur to a greater extent than with longer waves. Upon the assembly of each two units with their repeater coupling it should be observed that the tuning of the first anode circuit is particularly well accomplished, that the two-stage unit is screened off by metal, and the second anode circuit arranged outside of the screening system, the latter for the purpose of avoiding back-couplings.

The coupling between the high frequency multi-stage valves according to the invention, or with the following rectifier and low frequency amplifying device, is effected preferably through the medium of a tunable oscillating choke coupling, i. e., a coupling which consists of the parallel connection of an oscillating choke, a tuning condenser and a damping resistance. The tuning and the damping regulation is necessary for compensating unsymmetries and for obtaining the sufficient width of band. The coupling devices are preferably screened off, in the same manner as other parts of the entire arrangement, more particularly the multi-stage valves, oscillatory circuits, suppressing chokes and the like.

For the purpose of obtaining an adequate width of band and a maximum degree of regularity within this band, it is desirable to construct the oscillating choke so as to be irregular in form. This may be effected in such fashion for example that the winding elevation of the oscillating choke is at its largest on one end, and gradually decreases towards the other end. By means of this arrangement it is accomplished that the distributed capacities vary at single points of the oscillating choke, so that a sharp resonance is unable to occur. Although it is technically possible to so perform the assembly and the arrangement of the amplifier systems and oscillating chokes that a sufiicient width of band for the requisite wave range is obtained, it may be desirable to provide tuning for the oscillating choke, either for the purpose of performing ad- J'ustment of the wave band and the band width after completion of the receiving and amplifying device, or merely for the purpose of compensating certain unsymmetrical conditions. This tuning of the oscillating choke may be effected with any means of a known kind, for example by deformation of the coil by magnetic action on the outside, or by heating by means of eddy current or the like. For example, the windings of the coil may be secured with a certain tension, which upon heating by eddy current is caused to vary, so that in this manner alteration takes place in the relative position of the windings. Furthermore a capacitative or inductive action may be exerted from the outside through a window in the screening system. The alteration in the tuning may also take place through a window of this nature by means of an inductive loading.

The invention will be best understood by reference to the accompanying drawings, in which Fig. 1 shows a possible form of embodiment of an amplifier device. In Figs. 2 and 3 the structural arrangement of a two-stage valve is illustrated by way of example, Fig. 2 being an elevational view partially in section and showing the two systems and Fig. 3 the right hand side of the valve. Referring to Fig. 1 there are provided the two-stage high frequency valves A and B, and the rectifier valve C, which may be coupled with the additional amplifying means.

Coupled with the grid circuit L1, 01 of the first two-stage valve A through the medium of a very small condenser K, approximately in the order of 1 cm., is the aerial circuit. In the anode circuit of the first system of the two-stage valve A, and also the two-stage valve B, there are connected oscillating chokes D. Between the anode of the first system and the grid of the second system there are connected the repeater condensers Cu, which are preferably in the order of approximately 50 cm. Between the two-stage.

valves A and B and also between the two-stage valve B and the audion C there are connected the coupling devices E and F, which consist of the choke coils L2 and L3, respectively connected with which in parallel are the tuning capacities C2, or C3 and the damping resistances R2 and R3. At all points in the leads there are connected suppressing chokes D7, and in the heating circuits suppressing chokes DH- Immediately behind the coupling elements the single leads are connected by means of condensers with each other and with the screening means. As disclosed by Fig. 1, condensers of this kind are connected immediately behind the grid circuit L1, C1, at the leading-in point of the screening grid, at the connection for the oscillating choke, etc,, the same all being passed to a common point. For the sake of facilitated illustration these points P1 and P2 are not shown in the drawings as points, but as thick lines, but it is to be observed that in the practical execution the condensers are connected with one point of the screening system. These condensers are preferably approximately 5,000 cm.

The two systems in one two-stage valve are screened by a screening Wall against stray coupling. The lead ZA2 of the anode of the second system is passed out of the bulb at the top. In this manner the disturbing reactions may be kept very much smaller than in the case of common passage through the bottom of the socket. The separate lead-out also offers the advantage of ready conduction, with little disturbing ca pacity, to the next unit or to the rectifier respectively. The screening grids are made particularly long, and are formed into an equipotential area by a plurality of longitudinal wire connections. The cathodes are produced according to the latest experience as highly emissive barium cathodes with indirect heating, and are connected together in the shortest way.l These systems in connection with the two-stage valves, and in particular the size and arrangement and the spacing between the electrodes, may be executed in different ways, and adapted to the particular conditions prevailing, more particularly the capacities occurring.

Since the arrangement according to the invention results in a suflicient width of band as regards a two-stage valve and a one million period modulation band width is quite adequate even for very complete television transmission, the connection of a second tuned output circuit and the series connection of a plurality of these systems, as illustrated in the drawings, is quite permissible. The resulting half-value width may readily be made in an arrangement of this kind greater than 10 periods, a value which would seem quite sufficient even for very complete form of television transmission.

The structural arrangement of a two-stage valve is disclosed by Fig. 2. The two systems (on the right the first system, on the left the second system) are separated from each other by means the control grids Sh, or Sta, and the cathodes K1, or K2. In front of the first system there is arranged the oscillating chpke D, the windings of which are spaced apart to a greater extent at the top than at the bottom. Between the screen S on the one hand and the first valve system and the oscillating choke D on the other hand there are arranged the remaining coupling elements, the coupling condenser Cd and the resistance leak Rgz. The coupling condenser Cit is connected in immediate fashion with the anode A1. The lead Z Site from the control grid Stz is con nected with the coupling condenser Cit and the grid resistance Rgz. The remaining leads are notv particularly shown, as not being important.

The use of one of these valves in connection with a normal audion provides in itself the ex pected essential improvement in the reception with at the same time simplified operation. In the case of cascade connection of a plurality of units particular attention should be paid to mutual balancing-out, because the first stage of a semi-aperiodic amplifier would already take over the rectification, and pass on only the desired modulation band.

With the arrangement according to the invention it is possible in practice with two double valves and oscillatory circuit coupling to produce an approximately one hundredfold amplification and at the same time maintain a band width of approximately 500 kilo periods with '7 n1. carrier wave. With the assistance of this new amplifier it is accordingly possible, even with. low expenditure of energy on the part of the ultra-short wave transmitter, to utilize the same successfully for purposes of television, broadcasting and multiple modulation.

I claim:

1. In an ultra-short wave receiver for greater width of frequency-band, an ultra-short wave amplifier of at least two stages coupled with each other by means of an anode impedance semiaperiodically tuned for said width of band, a coupling condenser and a grid leak resistance, said anode impedance being an oscillating choke having a varying pitch of turn for obtaining nonuniformly distributed capacity thereby producing a natural frequency band in the order of the ultra-short wave and of sufficient width of band.

2. In an ultra-short wave receiver for greater width of frequency-band, an ultra-short wave amplifier having at least two stages coupled with each other by means of an anode impedance semi-aperiodically tuned for said width of band, a coupling condenser and a grid leak resistance, said anode impedance being an oscillating choke having a varying pitch of turn for obtaining nonuniformly distributed capacity thereby producing a natural frequency band in the order of the ultra-short wave and of suificient width of band, additional tuning means for performing adjustment of the wave band and of the band width of said oscillating coil and for compensating unsymmetrical conditions.

3. In an ultra-short wave receiver for greater width of frequency-band, an ultra-short wave amplifier having at least two stages coupled with each other by means of an anode impedance semi-aperiodically tuned for said width of band, a coupling condenser and a grid leak resistance, said anode impedance being an oscillating choke having a varying pitch of turn for obtaining non-uniformly distributed capacity thereby producing-a natural; feque-nc-y band in the order of the ultra-short wave and of sufficient width of band, additional: means for performing adjustment of the'wave band and of the band width of said oscillating coil and for compensating unsymmetrical conditions by altering the distance of the turns of said oscillating coil.

4. In an ultra-short wave receiver for greater width of frequency-band, an ultra-short wave amplifier having at least two stages coupled with each other by means .of' an anode impedance semiaperiodically tuned for. said width of band, a coupling condenser and a grid leak resistance, said anode impedance being an oscillating choke having a varying pitch of turn for obtaining nonuniformly. distributed capacity thereby producing a naturalrfrequency band in the order of the ultrashort wave and of suflicient width of band, additional tuning means for performing adjustment of the wave band and of the band width of said oscillating coil and for compensating unsymmetrical conditions bridging condensers being provided in the cathode connections of said stages for obtaining the shortest high-frequency paths, one pole of said bridging condensers being connected to the screen including said amplifier.

5. In an ultra-short wave receiver for greater width of frequency-band, an ultra-short wave amplifier having at least two multi-stage tubes,

each of which contains two ultra-short Wave amplifier stages coupled with each other by means of an anode impedance semi-aperiodically tuned for said width of band, a coupling condenser and a grid leak resistance, said anode impedance being an oscillating choke having a varying pitch 1- of turn for obtaining non-uniformly distributed capacity thereby producing a natural frequency band in the order of the ultra-short wave and of sufiicient width of band, said multi-stage tubes being coupled with each other by means of a tuned circuit, a coupling condenser and grid leak resistance, said tuned circuit consisting of an oscillating choke, a tuning condenser: and a damping resistance for producing a natural frequency band of said tuned circuit in the order of the ultra-short wave and of sufficient width of band.

6. In an ultra-short wave receiver for greater width of frequency-band, an ultra-short wave amplifier having at least two multi-stage tubes. each of which contains two ultra-short wave amplifier stages coupled with each other by means of an anode impedance semi-aperiodically tuned for said width of band, a coupling condenser and a grid leak resistance, said anode impedance being an oscilating choke having a varying pitch of turn for obtaining non-uniformly distributed capacity thereby producing a natural frequency band in the order of the ultra-short wave and of suflicient width of band, said multi-stage tubes being coupled with each other by means of a tuned circuit, a coupling condenser and a grid leak resistance, said tuned circuit consisting of an oscillating choke, a tuning condenser and a damping resistance for producing a natural frequency band of said tuned circuit in the order of the ultra-short wave and of sufficient width of band, said ultra-short-wave amplifier having an enclosing screen and bridging condensers provided in the cathode connections of said stages for obtaining the shortest high-frequency paths, one pole of said bridging condensers being connected to the screen including said amplifier.

7. In an ultra-short wave receiver for greater width of frequency-band, an ultra-short wave ameach other by means of an anode impedance semi-aperiodically tuned for said width of band, a coupling condenser and a grid leak resistance, said anode impedance being an oscillating choke having a varying pitch of turn for obtaining nonuniformly distributed capacity thereby produc ing a natural frequency band in the order of the ultra-short wave and of sufficient width of band, additional means for performing adjustment of the wave band and of the band width of said oscillating coil and for compensating unsymmetrical conditions by altering the distance of the turns of said oscillating coil by using electromagnetic forces.

8. In an ultra-short wave: receiver for greater width of frequency-band, an ultra-short wave plifier having at least two stages coupled with amplifier having at least two stages coupled with each other by means of an anode impedance semi-aperiodically tuned for said width of band, a coupling condenser and a grid leak resistance, said anode impedance being an oscillating choke having a varying pitch of turn for obtaining nonuniformly distributed capacity thereby producing a natural frequency band in the order of the ultra-short wave and of suflicient width of band, additional means for performing adjustment of the wave band and of the band width of said oscillating coil and for compensating unsymmetrical conditions by altering the distance of the turns of said oscillating coil by using an additional heating effect, causing change of the op 15 erative length of said coil.

MANFRED VON ARDENNE.

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