Quote:
Originally Posted by old_tv_nut
FYI, the speed of propagation in a transmission line is determined by the amount of inductance and capacitance per unit length, and the matched impedance is determined by their ratio. The luminance delay line has a coiled conductor to increase the inductance compared to a regular coax, and the conductor is wound over a grounded conducting sheet to increast the capacitance. The result compared to coax is much greater delay in a shorter, smaller device. An increased inductance / capacitance ratio also makes the impedance higher than 75 ohms, to work better with typical tube circuits. In this case the line is apparently designed for 1800 ohms (R64 in parallel with R63.) When a transmission line is matched on both ends, there is a 6 dB loss. This sort of synthetic delay line usually has some added attenuation at high frequencies and is not perfectly matched at high frequencies either. These shortcomings are compensated by the various coils you see on the output end.
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The delay lines for these sets seems to be another impossible thing to find, should someone ever need to replace one.
I remember being amazed when i started to see them made out of quartz in newer sets, still cant quite get my head around how that works.
