US4007480A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Color television receiver beat frequency control using stabilized television transmitter aural carrier
Assignee: WEST MICHIGAN TELECASTERS Inc
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Filing: 1975-09-17
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Granted: 1977-02-08
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Expires: 1995-09-17
Abstract
Abstract Interference in a television receiver due to variations in the frequency of a "920 KHz beat" frequency obtained from the difference in frequency between the 4.5 MHz intercarrier frequency and the 3.58 MHz color subcarrier frequency and detected by the receiver's video detector is reduced by using a color television transmitter having an aural oscillator using a crystal of a smaller size, an "AT" cut and higher frequency followed by frequency division of the oscillator output. The resulting output signal has improved frequency stability and is used as a basis for aural modulation in the television transmitter.
Inventors
- 👤 Dale Wolters
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 05:05
CPC Classifications
H; H04; H04N; H04N5/00; H04N5/38; H04N5/42; H03; H03B; H03B2200/00; H03B2200/0002; H03B2200/0012
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
181 words
In combination with a color television transmitter, an aural carrier frequency generating device, for generating the aural carrier of said color television transmitter, comprising: a proportionally controlled oven; an "AT" cut crystal oscillator housed in said oven having a frequency of from about 1MHz to 10MHz, including means for generating a square wave signal and converting the square wave signal to a sine wave signal of the same frequency; a frequency dividing network whereby the output of the oscillator is divided by an amount equal to the factor by which the frequency produced by the crystal oscillator is greater than the frequency desired for aural modulation, thereby reducing frequency variations in the aural carrier to substantially eliminate frequency variations in the best frequency in a color television receiver between the aural carrier and a signal of another frequency; and a frequency multiplying means coupled to said frequency dividing network for multiplying the output of said frequency dividing network so the frequency output of said multiplying means falls within the 54 to 88 MHz or 174 to 216 MHz television broadcast frequencies.
Claim 2
Dependent Claim
181 words
In combination with a color television transmitter, an aural carrier frequency generating device, for generating the aural carrier of said color television transmitter, comprising: a proportionally controlled oven; an "AT" cut crystal oscillator housed in said oven having a frequency of from about 1MHz to 10MHz, including means for generating a square wave signal and converting the square wave signal to a sine wave signal of the same frequency; a frequency dividing network whereby the output of the oscillator is divided by an amount equal to the factor by which the frequency produced by the crystal oscillator is greater than the frequency desired for aural modulation, thereby reducing frequency variations in the aural carrier to substantially eliminate frequency variations in the best frequency in a color television receiver between the aural carrier and a signal of another frequency; and a frequency multiplying means coupled to said frequency dividing network for multiplying the output of said frequency dividing network so the frequency output of said multiplying means falls within the 54 to 88 MHz or 174 to 216 MHz television broadcast frequencies.
Claim 3
Dependent Claim
30 words
A color television transmitter as recited in claim 1 wherein said crystal oscillator includes electronic tuning to permit frequency adjustment of the crystal output frequency to compensate for crystal aging.
Claim 4
Dependent Claim
41 words
A color television transmitter as recited in claim 1 wherein said crystal oscillator includes an automatic gain control circuit for maintaining the magnitude of the crystal current sufficiently low for good long term stability and sufficiently high for good phase stability.
Claim 5
Dependent Claim
27 words
A color television transmitter as recited in claim 1 wherein the frequency of said crystal oscillator is approximately 7.1032096 MHz for use in broadcasting television channel 13.
Claim 6
Dependent Claim
32 words
A color television transmitter as recited in claim 4 wherein said frequency dividing network divides the input from said crystal oscillator by 32 to produce an output frequency of approximately 211.9753 KHz.
Claim 7
Dependent Claim
36 words
A color television transmitter as recited in claim 5 wherein said frequency multiplying means multiplies the output of said frequency dividing network by 972 so the frequency output of said multiplying means is approximately 215.76 MHz.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-02-08 | 1980-08-09 | 1981-02-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-02-08 | 1984-08-09 | 1985-02-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-02-08 | 1988-08-09 | 1989-02-08 | $7700.00 | Window Closed / Lapsed |