US1907478A - Amplification system - Google Patents

Amplification system Download PDF

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Publication number
US1907478A
US1907478A US151722A US15172226A US1907478A US 1907478 A US1907478 A US 1907478A US 151722 A US151722 A US 151722A US 15172226 A US15172226 A US 15172226A US 1907478 A US1907478 A US 1907478A
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United States
Prior art keywords
frequency
radio
frequencies
primary
transformer
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US151722A
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English (en)
Inventor
George L Beers
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Westinghouse Electric Corp
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Westinghouse Electric Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to NL24590D priority Critical patent/NL24590C/xx
Application filed by Westinghouse Electric Corp filed Critical Westinghouse Electric Corp
Priority to US151722A priority patent/US1907478A/en
Priority to GB30714/27A priority patent/GB281633A/en
Priority to US590163A priority patent/US1973037A/en
Application granted granted Critical
Publication of US1907478A publication Critical patent/US1907478A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/06—Receivers
    • H04B1/16—Circuits
    • H04B1/163—Special arrangements for the reduction of the damping of resonant circuits of receivers
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03J—TUNING RESONANT CIRCUITS; SELECTING RESONANT CIRCUITS
    • H03J3/00—Continuous tuning
    • H03J3/02—Details
    • H03J3/06—Arrangements for obtaining constant bandwidth or gain throughout tuning range or ranges

Definitions

  • WITNEJSSES -/fz'l0 Cycles From fiesonantF'requency- INVENTOR George. L,.Be eIS.
  • My invention relates to amplification systems, and it has particular relation to a system designed for voltage amplification at radio frequencies.
  • One object of my invention is to improve the selectivity characteristics of a radio-frequency amplifying system.
  • Another object of my invention is to improve the voltage amplification characteristics of a radio-frequency amplifying system.
  • Another object of my invention is to provide an improved radio-frequency transformer.
  • Another object of my invention is to provide a radio-frequency amplifying system that will be reasonably selective over the entire range of frequencies now used in radio broad-casting, and, at the same time, give a substantially equal voltage amplification over the same range.
  • Another object of my invention is to provide a radio-frequency amplification system that is inherently stable and does not tend to oscillate over the range of frequencies for which it is designed.
  • a radio-frequency transformer of the usual type,having a lowinductance primary is extremely selective at the lower-frequency end of the range, since the radio-frequency resistance of the secondary is many times less at such lower frequencies than it is .at the high-frequency end.
  • ⁇ Vith an amplifying system of but one or two stages, the distortion is very pronounced at the lower frequencies by reason of the cirtremc selectivity preventing the side bands from being etliciently amplified.
  • the resonance curve at any given radio-frequency over the tuning range, shall be from 8 to 10 kilocycles wide at 80 or 90% of the peak or resonancecurrent value.
  • radio-frequency transformers of the usual type input frequencies one, or one and 5 one-half kilocycles above or below the frequency to which the secondary may be tuned at the low-frequency end of the range will give approximately 90% of the resonance current, while, at the high-frequency end of the range, the input frequencies may vary as much as fifty kilocycles above or below resonance and still give secondary currents 90% of the resonance current.
  • the selectivity at high frequencies may be somewhat improved by using several stages, but the improvement is not suflicient to be satisfactory.
  • Signals from the high-frequency stations when received without interference, are not appreciably distorted, but distortion is very 95 noticeable on signals from stations broadcasting at frequencies lying toward the lower end of the frequency range.
  • Figure 1 is a diagrammatic view of a preferred form of my invention incorporated into a multi-stage radio-frequency amplifying system
  • Fig. 2 is a sectional view of a preferred form of inter-tube transformer
  • Fig. 3 is a diagram illustrating graphically the difference between the voltage amplification characteristics of my improved coupling system and systems of the prior art
  • Fig. 4 is a diagram showing curves illustrative of the selectivity characteristics of the usual low-inductance primary radio-frequency transformer
  • Fig. 5 is a diagram showing curves illustrative of the selectivity characteristics of my improved transformer.
  • a thermionic device having a filament 2, a grid 3 and aplate 4, is provided with an input circuit comprising an inductor 5 shunted by a tuning condenser 6.
  • the inductor 5 may be a oop. or it may be a coupling inductor of any well known type, associatedwith an antennaground circuit (not shown).
  • One end of the inductor 5 is connected to the grid by a conductor 7 a conductor'8 leads from an intermediate portion of the inductor 5 through a grid biasing battery 9 to the filament 2, and the opposite end is connected to the plate 4 through a small variable or fixed condenser 11.
  • An inductor 12 which is the primary of a radio-frequency transformer 13, is connected between the plate 4 and the filament 2, a battery 14 supplying plate potential.
  • a battery 15 in series with a rheostat 16 supplies filament power, and the same battery also may be utilized to energize the filaments of from an intermediate point thereon, through a grid-biasing battery 27, to the filament 19.
  • Plate potential for the thermionic device is supplied from the battery 14:, the primary 28 of a radio-frequency transformer 29 being connected between the battery and the plate.
  • the secondary 31 of the transformer 29 is shunted by a tuning condenser 32 and is connected to the remaining portion of the system by conductors 33 and 34.
  • the two tuned radio-frequency amplifying stages may be followed by additional radio-frequency stages, or by a detector and audio-frequency amplifier.
  • the additional apparatus is optional, and, since it may follow conventional lines, if desirable, is merely indicated by a rectangle 35.
  • the ratio of reactance to radiofrequency resistance of the secondary be made at least so high that primary frequencies five kilocycles on each side of resonance do not induce currents of more than 80% of the resonance value in the secondary.
  • Curve C represents the voltage across the secondary tuned to 600 kilocycles, with varying input frequencies, and it is significant to note that a frequency five kilocycles away tunable.
  • Curve D illustrates the fact that the high-frequency end of the range in the usual transformer is much less selective than at the low-frequency end, frequencies five kilocycles away from resonance at 1-150 kilocycles giving approximately of the resonance voltage.
  • I preferably lower the resonance frequency of the primary to a point near or below the lowest frequency to which the secondary is tunable.
  • Such a primary does not increase the effective resistance of the secondary at' high frequencies but does increase the efiective resistance thereof at low frequencies.
  • the effective resistance thus introduced compensates the decreased damp-' ing resulting from the decreased radio-frequency resistance of the secondary at lower frequencies and broadens the tuning at such frequencies.
  • Curves E and F summarize the results of a large number of tests made on my improved transformer. It will be noted from these curves that the selectivity at both the high-frequency end and the low-frequency end of the range is substantially the same, the relative displacement between the two curves never becoming greater than one tenth of the maximum resonant voltage.
  • the tuning condenser shunting the secondary should have a maximum capacity of 550 micro-.microfarads and a minimum capacity of 15-20 micromierofarads or less.
  • my preferred transformer comprises a primary 40 of 250 turns of #30 double-cotton-covered wire, in the form of a duo-lateral coil, and a secondary 41 of 72 turns of #24 double-cotton-covered wire wound as a single-layer solenoid.
  • the inside diameter of both primary and secondary is two inches and they are preferably separated @ths to Z inches axially.
  • the curve A in Fig. 3 illustrates graphically the voltage-amplification characteristics of a transformer constructed according to my invention, while the curve B illustrates the characteristics of a transformer having the usual low-inductance primary.
  • An amplifying system constructed according to my invention is relatively stable. At the higher frequencies, the reactance of the high-inductance primaries in the plate circuits of the tubes is predominately capacitive and, consequently, the conditions for negative feed-back are present. In order, therefore, that the system shall amplify efficiently, a certain amount of positive feedback should be supplied and this feed-back is most conveniently introduced by utilizing a small condenser between the plate electrode and one end of the inductor associated with the grid of the same tube.
  • the action of this arrangement is different from that of the Rice Patent 1,334,118, although diagrammatically they are similar in appearance.
  • the neutralizing condenser and that portion of the grid inductor included between the connection from the filament and the connection to the condenser cooperate to place, on the grid of the tube, potentials equal and opposite in phase to potentials placed thereonby reason of the tube-capacity coupling between the input and the output circuits in order that regenerative feed-back shall be compensated.
  • the normal reactance-of the plate circuit is capacitive, tending toward dc-generation, instead of toward regeneration and oscillation, and the condenser 11 in combination with the por tion of the winding with which it is connected, act to produce a regeneratiye feedback.
  • the circuit arrangement is diagrammatically like that of the Rice patent, the effect of the condenser and its associated coil is regenerative after the well known Weagant regenerative circuit.
  • the capacity coupling may be greatly increased by placing the grid and plate ends of the respective windings so they are adjacent, provided the relative direction of the windings is such that the capacity coupling is in proper phase.
  • the voltage-amplification characteristics of the transformer may be appreciably altered, inasmuch as there is a considerable transfer of energy at the higher frequencies across the inter-winding capacity.
  • An optimum spacing can be determined for each transformer, the spacing 42 for the specific transformer illustrated in Fig. .2 being approximately @ths inches.
  • radio-frequency amplification system which has a. substantially straight-line selectivity-characteristic over the range of frequencies for'which it is designed.
  • My improved coupling system may also be given an approximately straight-line voltage-amplification characteristic, although it is somewhat preferable to have a higher voltage step-up at the lower fre uencies.
  • y improved system is also remarkably free from parasitic oscillations, and, although preferably utilizing a feed-back means analogous to the usual neutralizing condenser and 00 associated network, such means is not primarily for the purpose of neutralizing the system against oscillations.
  • a radio-frequency amplification system a plurality of thermionic devices, and coupling means between two of said devices com rising a transformer having a secondary 1n the form of a single layer solenoid, and a primary in the form of a multi-layer coil which is resonant at a frequency outside of the band of frequencies within which saidtamplification system 'is designed to funcion.
  • a radio-frequency amplification system comprising a plurality of thermionic devices, coupling means therebetween comprising a primary of such a value of inductance-that the predominant reactance thereof at high frequencies is capacitive, and means for balancing the negative feed-back caused by such reactance.
  • a plurality of thermionic devices coupling means between two of said devices comprising a transformer having a primary winding the natural period of which is lower than the lowest frequency the system is intended to amplify, a secondary winding, means for tuning said secondary winding and means for transferring energy from the output circuit that includes the primary winding to the input circuit of the device to which said output circuit pertains.
  • a radio-frequency amplification system comprising a plurality of thermionic devices, coupling means therebetween comprising a primary winding of such value of inductance that the predominant reactance thereof at high frequencies is capacitive, means for balancing the negative feed-back caused by such reacta nce, and a tunable secondary wind- 6.
  • a radio-frequency amplificaton system a plurality of thermionic devices, cou-' pling means between certain of said devices for inductive and capacitative transfer of energy therebetween in aiding sense and additional means for transferring energy from the output to the inputcircuit of one of said devices.
  • a radio-frequency amplification system a plurality of thermionic devices, coupling means between certain of said devices for inductive and capacitative transfer of energy therebetween in aiding sense, said means being constituted by a primary Winding having high distributed capacity and a tunable secondary winding, and means for transferring energy from the output circuit to the input circuit of one of said devices in the sense to promote regeneration.
  • a plurality of thermionic devices, coupling means therebetween consisting of a multi-turn primary winding having large distributed capacity disposed in inductive and capacitative relation to a tunable secondary winding, said secondary winding being so connected to the input terminals of one of said thermionic devices that the energy transferred between said devices through inductive and capacitative coupling is in aiding sense.
  • a radio-frequency amplification system comprising a plurality of thermionic devices, coupling meaiis between adjacent devices comprising a primary winding of such a value of inductance that the predominant reactance thereof at high frequencies is capacitive, and a tunable secondary winding, the coupling between said primary and secondary windings being such that the effective resistance of the tunable secondarv is greater at the lower frequencies in the tuning range of the said secondary than it would be if the reactance of the primary at high frequencies were predominantly inductive, whereby the effective resistance of the secondary is substantially constant over the tuning range thereof and the selectivity of the system is substantially uniform.
  • a tuned radio frequency amplifier having an input circuit and having an output circuit whose reactance is condensive, said output circuit delivering power to a tuned circuit, and means for feeding back power to the input circuit so as to eliminate the damping effect on said input circuit of the capacity reactance of said-output circuit.
  • an output circuit of an electron discharge device whose reactance is negative, the output circuit feeding power to a tuned secondary circuit, a feed back coil and current limiting condenser connected in series between the anode and cathode of the on the input circuit of said tube, and means including a path between the output and input circuits for counteracting said damping effect.
  • a thermionic tube In an amplifier, a thermionic tube, a tunable input circuit therefor, an output circuit therefor comprising a coil whose inductance is so great that the output current of the tube tends to flow through the natural capacity of the coil causing a damping effect on the input circuit of said tube, and means for counteracting said damping effect, said means comprising an inductance and a condenser in series, said last mentioned inductance being magnetically coupledto the input circuit of said tube.
  • a tuned radio frequency amplifier having an input circuit and an output circuit, the latter having a negative reactance
  • a space discharge device an input circuit therefor, an output circuit therefor including a reactance which exercises a damping effect on the said input circuit, and a path including a pair of reactances between the output and input circuits for counteracting said damping effect, one of said reactances being variable.
  • a spaced discharge tube including a tunable input circuit and an output circuit, a coil in said output circuit naturally resonant to a frequency outside a circuits for counteractin In testimony whereo I have. hereunto said effect.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Amplifiers (AREA)
  • Microwave Amplifiers (AREA)
US151722A 1926-11-30 1926-11-30 Amplification system Expired - Lifetime US1907478A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
NL24590D NL24590C (enrdf_load_stackoverflow) 1926-11-30
US151722A US1907478A (en) 1926-11-30 1926-11-30 Amplification system
GB30714/27A GB281633A (en) 1926-11-30 1927-11-15 Improvements in or relating to electrical amplification systems
US590163A US1973037A (en) 1926-11-30 1932-02-01 Amplification system

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US151722A US1907478A (en) 1926-11-30 1926-11-30 Amplification system

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US1907478A true US1907478A (en) 1933-05-09

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US151722A Expired - Lifetime US1907478A (en) 1926-11-30 1926-11-30 Amplification system

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US (1) US1907478A (enrdf_load_stackoverflow)
GB (1) GB281633A (enrdf_load_stackoverflow)
NL (1) NL24590C (enrdf_load_stackoverflow)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3125285A (en) * 1964-03-17 Safety device for refrigeration compressors

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3125285A (en) * 1964-03-17 Safety device for refrigeration compressors

Also Published As

Publication number Publication date
GB281633A (en) 1928-06-14
NL24590C (enrdf_load_stackoverflow)

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