Color subcarrier frequency comparator

DETAILED DESCRIPTION In a conventional television network, a transmitter located at the station modulates a radio frequency signal with a color burst for each scan of a television receiver.
The color burst is derived from an atomically controlled oscillator located at the network origination point.
The RF signal is demodulated in a conventional television receiver where the color oscillator is phase-locked to the recovered color bursts.
In this way, the color oscillator in the receiver is phase-locked to an atomically controlled oscillator.
It is an object of the present invention to provide an apparatus for measuring the frequency of a reference signal, which utilizes as a standard frequency signal the precision color subcarrier signal of a conventional color television receiver.
Another object of the present invention is to provide a precision frequency/phase comparator which provides a means for adjusting a local frequency standard to an accuracy of at least .
+-.
1 .
times.
10.
sup.
10 in less than 100 seconds by utilizing as a standard frequency signal the color subcarrier signal of a television receiver, which is phase-locked to a network atomically controlled color subcarrier signal.
These and other objects are attained in accordance with the present invention by the provision of an apparatus in which a synthesizer produces bursts of a color subcarrier signal which is phase-locked to the reference signal to be calibrated or measured.
The synthesized subcarrier signal is gated at the horizontal line rate of a conventional television receiver and is used to amplitude modulate the RF signal received from a television network.
The modulated signal is applied to the receiver and is processed as normal picture chrominance information which appears on the screen of the receiver as a modulation bar.
When the frequency difference between the synthesized and broadcast subcarrier signals is large, the modulation bar will move to the left on the screen if the synthesized frequency is high compared to the frequency of the broadcast signal and to the right if the synthesized frequency is low