US2217929A - Keying circuit - Google Patents

Keying circuit Download PDF

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Publication number
US2217929A
US2217929A US240641A US24064138A US2217929A US 2217929 A US2217929 A US 2217929A US 240641 A US240641 A US 240641A US 24064138 A US24064138 A US 24064138A US 2217929 A US2217929 A US 2217929A
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United States
Prior art keywords
resistance
tube
keying
stages
cathode
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Expired - Lifetime
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US240641A
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English (en)
Inventor
Wassell Harold Joseph Hughes
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RCA Corp
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RCA Corp
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Publication date
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Publication of US2217929A publication Critical patent/US2217929A/en
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/02—Amplitude-modulated carrier systems, e.g. using on-off keying; Single sideband or vestigial sideband modulation
    • H04L27/04—Modulator circuits; Transmitter circuits

Definitions

  • This invention relates to keying circuit arrangements for radio and like transmitters and has for its object to provide improved keying circuits for radio and the like transmitters of the kind wherein there isa plurality of high frequency stages in cascade one or more of said stages being keyed in and out of the cut-off condition thereby to remove the high frequency drive from a succeeding stage or stages and one or more of the succeeding stages being simultaneously keyed in and out of a condition in which considerable dead loss current is taken, thereby improving the regulation since, when the high frequency drive is cut oil by an early stage or stages, the total load upon the energizing power source is still maintained at a value more or less approximating to, or a considerable percentage of, that obtaining prior to such out off, by the action of the dead loss tube or tubes.
  • dead loss current By the term dead loss current, applicant means power loss in the anode circuit of a valve under directcurrent conditions.
  • the necessary changes in the operating conditions of the stages are brought about by suitably changing the grid biasses upon the stages in question, the usual practice being to derive the biasses from a resistance which is in series with a keying tube and suitable anode voltage supply source therefor, the grid potential of the keying tube being controlled by a key or the like which accordingly controls the current flow through the said resistance and therefore the biasses applied to the high frequency stages.
  • Such a known circuit arrangement offers the practical defect that the said resistance must be of low value as compared to the grid 'impedances of the high frequency stage since high frequency stage grid currents flowing in the mark condition must flow through the said resistance.
  • the necessity for a low 'value of resistance in turn involves a necessity for a high current flow therethrough to develop the required bias potentials therein and this in its turn involves the use of a large and expensive keying tube and associated anode potential source.
  • the principal object of this invention is to avoid the above defect.
  • a keying circuit for a radio or like transmitter of the kind referred to and wherein the two required keying biasses for the high frequency tubesnamely the cut-off bias for one stage or stages and the dead loss bias for a later stage or stages-are obtained from a potentiometer resistance in circuit with a I keying tube is characterized in that there are also provided two auxiliary tube stages connected to receive controljbiasses from said resistance one of 1 said auxiliary tube stages being shuntedbetwee'n the point of application of one of said keying biasses and the end ofsaid resistance and the other of said auxiliaryitubes being shunted between the point of application of the other of said keying biasses and said resistance and the biasses applied to said auxiliary tube stages, in keying, being such as to render them conductive when grid currents are occasioned in the appropriate high frequency stages.
  • my invention provides'two paths through which it may flow, i. e., the additional tube impedances and the said resistance.
  • the grid circuits of the second, third and fourth stages '2, 3, 4 are connected to the cathode 6 of a first auxiliary tube T whose anode 8 is connected to earth and to the cathode 9 of a keying tube Ill.
  • the grid circuit of the fifth stage 5 is connected to the cathode ll of a second auxiliary tube I2 whose anode I3 is also connected to the cathode 9 of the keyingtube III.
  • a bias source I in series with a key l5 (or relay contacts) is connected in the grid-cathode circuit of the keying tube I 0 whose anode-cathode circuit consists of an anode potential source IS in series with a potentiometer resistance l'l.
  • Any other keying means well known per se may, of course, replace the bias source and key or relay contacts in the grid-cathode circuit of the keying tube "I.
  • the end [8. (or a point near the end) of the resistance l1 adjacent the negative terminal of the anode potential source 16, is connected to the control grid l9 of the first auxiliary tube 1 the cathode 6 of. which is connected to a point 20 further down on the resistance H.
  • auxiliary tube 12 is connected to a point 22 near the earthed end of the resistance l1 and the cathode H of said auxiliary tube I2 is connected to a point 21 still nearer said earthed end.
  • all the points I8, 20, 22, 23 on the potentiometer resistance l1 may be made adjustable as indicated.
  • the said tubes In the mark" condition (when the keying tube II is not conductive and accordingly the grids of the auxiliary tubes 1, ii are at approximately the same potentials as the associated cathodes) the said tubes present low internal resistances and thus allow the major portion of the grid current from the high frequency stages'to flow throu them in preference to flowing through the relatively high potentiometer resistance H.
  • the positions of the taps I8, 20, 22, 23 are so chosen that at.spaee" (when the keying tube l becomes nductive), the auxiliary tubes are biassed to Rt oil and at the same time the cathodes of said tubes assume the potentials necessary for the (second, third and fourth stages 2, I, l, to swing to cut-off and the fifth stage 5, to dead loss.
  • resistance II can be made of quite high value, while the keying tube Hi can be quite small and the anode potential source [6 therefor also small, e. g. capable of supplying only a few milliamperes.
  • a plurality of relay stages each comprising a tube having a control grid and cathode, a source of potential and a resistance connected in a series circuit, means connecting points on said resistance between the cathode and control grid of at least one of said tubes, an additional tube having its impedance connected between points on said resistance, to shunt a portion of said resistance connected between said control grid and cathode, an impedance variable at signal frequency in shunt to said series circuit, said variable impedance serving to vary the potential drop in said resistance and the bias between said control grid and cathode to grid of said additional be appreciated the potentiometer render the said first tube conductive or non-com.
  • a plurality of relay stages each comprising a device having a control grid and cathode, a source of potential and a resistance connected in a series circuit, means connecting points on said resistance between the cathode and control grid 0!
  • variable impedance serving to vary the potential drop in said resistance and thereby vary the bias between the control grids and cathodes of said devices to vary the conductivity thereof between a high and low value and connections between the control grids of said first and second tubes and said resistance at points on said resistance which bias said additional tubesby potentials such that the impedances thereof are low when said devices are highly conductive.
  • variable impedance comprises a keying tube having an anode, a cathode, and a control grid, means connecting the anode and cathode .of said keying tube with said series circuit, and means connecting the control grid of said keying tube to a source of variable potential.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Microwave Amplifiers (AREA)
  • Transmitters (AREA)
US240641A 1937-12-01 1938-11-16 Keying circuit Expired - Lifetime US2217929A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB33249/37A GB506658A (en) 1937-12-01 1937-12-01 Improvements in or relating to keying circuit arrangements for radio and like transmitters

Publications (1)

Publication Number Publication Date
US2217929A true US2217929A (en) 1940-10-15

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ID=10350460

Family Applications (1)

Application Number Title Priority Date Filing Date
US240641A Expired - Lifetime US2217929A (en) 1937-12-01 1938-11-16 Keying circuit

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US (1) US2217929A (enrdf_load_stackoverflow)
GB (1) GB506658A (enrdf_load_stackoverflow)
NL (1) NL61923C (enrdf_load_stackoverflow)

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Publication number Publication date
NL61923C (enrdf_load_stackoverflow)
GB506658A (en) 1939-06-01

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