Wayne is correct, I mistyped slightly. The reactance tube merely does the nudging in response to the phase detector, which is a pair of diodes exactly like in horizontal circuits. The phase detector is what is comparing the local signal to the incoming burst, producing an error signal used by the reactance tube. Little too much egg nog last night!
Here's another way to do it, the GE Porta Color chassis!
Instead of having a PLL (phase locked loop) as with RCA designs, GE decided to 'shock excite' the crystal directly with the incoming burst and allow it to ring on its own at the correct frequency. It's analogous to ringing a bell, in a way. This is what Tom was referring to earlier, and why I like this circuit so much. It's a much simpler way to go about it, all you do is gate the burst with a horizontal pulse from the flyback and route the signal from the ringing crystal to your detectors. In this case the detectors are silicon diodes not vacuum tubes, which along with the use of compactrons in the HE chassis drastically cut down on the number of tubes involved.
12-25-2014, 07:24 AM
Waitin' now for the 6LE8 high level demodulator story.
Hybrid Mode
