US2248753A - Frequency control system - Google Patents

Frequency control system Download PDF

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Publication number
US2248753A
US2248753A US266400A US26640039A US2248753A US 2248753 A US2248753 A US 2248753A US 266400 A US266400 A US 266400A US 26640039 A US26640039 A US 26640039A US 2248753 A US2248753 A US 2248753A
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US
United States
Prior art keywords
frequency
control
afc
bias
discriminator
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
US266400A
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English (en)
Inventor
Green Alfred Leonard
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.)
RCA Corp
Original Assignee
RCA 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
Application filed by RCA Corp filed Critical RCA Corp
Application granted granted Critical
Publication of US2248753A publication Critical patent/US2248753A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G3/00—Gain control in amplifiers or frequency changers
    • H03G3/20—Automatic control
    • H03G3/22—Automatic control in amplifiers having discharge tubes
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03J—TUNING RESONANT CIRCUITS; SELECTING RESONANT CIRCUITS
    • H03J7/00—Automatic frequency control; Automatic scanning over a band of frequencies
    • H03J7/02—Automatic frequency control
    • H03J7/04—Automatic frequency control where the frequency control is accomplished by varying the electrical characteristics of a non-mechanically adjustable element or where the nature of the frequency controlling element is not significant
    • H03J7/042—Automatic frequency control where the frequency control is accomplished by varying the electrical characteristics of a non-mechanically adjustable element or where the nature of the frequency controlling element is not significant with reactance tube

Definitions

  • is connected across resistors 3233, whereas condenser 34 is connected across resistor 33.
  • the cathode side of resistor 33 is at ground potential.
  • the cathode side of resistor 32 is connected by lead 36, the AFC lead, to a gain control electrode 39 of the frequency control tube 40.
  • a positive AFC bias voltage is thereby applied to grid 39 in control valve 40, the transconductance of control valve 40 increases and thereby the reactive effect of control valve 43 on the oscillator tank circuit I4 is changed.
  • This change in reactive effect is equivalent to a decrease in the virtual inductance shunted across the oscillator tank circuit Hi and is therefore accompanied by an increase in the frequency of the oscillator network l5.
  • the above-mentioned increase in oscillator frequency due to discriminator action is a desired AFC effect whereby the approximate setting of the uni-control mechanism 54 is electronically adjusted for fine tuning of the receiver to the incoming aerial signal.
  • the strength of the AFC action may be made very nearly independent of the intensity of the aerial signal. This follows since the amount of AFC, for a given change in discriminator bias applied to grid 39, depends on the value of the AVC bias applied to grid @5. Thus, for weak incoming carriers for which the differential discriminator bias is small for a given amount of mistuning, the AVC is simultaneously reduced so that the control valve works at a high level of transconductance. Assuming therefore that the control valve is adjusted to deal with relatively weak incoming carriers, it follows that the AFC action then remains approximately the same independently of the strength of the signal.
  • a superheterodyne receiver including a local oscillation tank circuit, an intermediate frequency energy utilization network, a frequency control tube operatively associated with the tank circuit, means producing a frequency correction voltage whose magnitude and polarity are respectively dependent on the amount and sense of departure of the intermediate frequency energy from an assigned frequency value, and means deriving a unidirectional voltage from signal energy Whose magnitude is a function of the signal carrier intensity; the improvement which comprises means applying said frequency correction voltage to said control tube in a sense to maintain said assigned frequency value, additional means applying said unidirectional voltage to said control tube to control the transconductance thereof, and said correction voltage producing means comprising a pair of rectifiers having separate input circuits coupled to said intermediate frequency network, and said input circuits being oppositely mistuned with respect to said assigned frequency value.

Landscapes

  • Channel Selection Circuits, Automatic Tuning Circuits (AREA)
  • Stabilization Of Oscillater, Synchronisation, Frequency Synthesizers (AREA)
US266400A 1938-04-08 1939-04-06 Frequency control system Expired - Lifetime US2248753A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
AU2248753X 1938-04-08

Publications (1)

Publication Number Publication Date
US2248753A true US2248753A (en) 1941-07-08

Family

ID=3838162

Family Applications (1)

Application Number Title Priority Date Filing Date
US266400A Expired - Lifetime US2248753A (en) 1938-04-08 1939-04-06 Frequency control system

Country Status (2)

Country Link
US (1) US2248753A (enrdf_load_stackoverflow)
FR (1) FR852659A (enrdf_load_stackoverflow)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2464818A (en) * 1943-05-27 1949-03-22 Sperry Corp Frequency control system

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2464818A (en) * 1943-05-27 1949-03-22 Sperry Corp Frequency control system

Also Published As

Publication number Publication date
FR852659A (enrdf_load_stackoverflow) 1940-03-04

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