I few days ago I asked about the significance of the P, E, B, and G markings on my junkbox Toyo CM 455 kc filter (1969 vintage). PA3BCB -- in yet another example of the power of the International Brotherhood of Electronic Wizards -- was the first to provide the needed info. And in another example of IBEW awesomeness, KA0LDB noted that the markings are explained in the 1971 RSGB Handbook.
P = Plate = filter input
B = B+ = mixer B+ plus if needed or input ground
G = Grid = filter output
E = Earth = Ground
I like the switched filter arrangement presented above (from the RSGB Handbook); the 2.4 kc bandwidth is great for SSB, but a little tight for AM. I might put in a DPDT switch in the circuit so as to be able to go back to the "broad as a barn door" selectivity provided by just the 455 kc IF cans.
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