I just received the service manual for my Zenith R-70 AM/FM portable radio. I looked at the schematic and am amazed at the sophisticated circuitry this set has--four IF stages on FM, two on AM, ceramic filters for both bands, push-pull audio output (and a 4-inch round speaker) . . . boy, talk about high-performance! The radio sounds great and pulls in stations on both bands like a magnet; now I know why. The only thing that puzzles me is why the AFC is fixed, rather than switchable (there is no AFC defeat switch on the front panel). Since this set has a ceramic filter in the FM section and four IF stages (two IFs on AM and a ceramic filter there as well), not to mention an FM RF stage--which would make it a heck of a performer in FM fringe or near-fringe areas, not to mention DX when the bands open up in spring, summer and early fall--why on earth didn't Zenith design this radio with switchable AFC? The set was built in 1980 and couldn't have been cheap when new. How much more would an AFC defeat switch have added to the price?
