Color television receiver beat frequency control using stabilized television transmitter aural carrier
AssigneeWest Michigan Telecasters Inc.
InventorDale Wolters
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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.
Claims6
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.
Dependencies are inferred from the claim text.