Re: Philco 444 coupling wires "X" and "Y"
As an aside, it's fascinating that simple but effective circuit elements like these are actually present, especially in what was presented as a basic low-cost receiver, in order to squeeze optimum performance out of it. I assume that X helped to even up coupling effectiveness across the band and that Y neutralised space-charge coupling within the heptode, optimising noise performance and minimising "pulling". Components of virtually zero cost but with sound technical justification for their presence, the essence of good production engineering.
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