Hello All,

I don't know if there are any Ham Radio guru's out there or EE's or just those who like to experiment with electronics. But I wanted to ask those about this radio design. Specifically the FM section. I've been trying to figure out why on Earth did they do "that" in the design.

Here's my questions relating to the FM section:

1. What possible benefit is having two tuned I-F cans coupled together with no amplifier stage between the Mixer and 1st I-F.

2. Why is there a diode almost acting as an AM detector in the 2nd FM I-F stage?

I was fortunate enough to find a cheap example of this radio on E-Bay, usually these darn 3rd gen AM-FM radios go for stupid amounts of money because of the special mounting in that only these radios will fit in the dash often to replace the AM only dealy the car came with.

Of course it's 48 years old and needs work. I have new electrolytic caps, am going to check the noise figure on the transistors and then do the AM and FM alignment. I just hope with the slugged tuned I-F cans the fixed caps are not the kind that suffer from the silver mica disease (silver migration), other wise what should take just a few hours will take a few days to sort that out.

Hopefully the schematic comes through below.

This is along the lines of the really unnecessary over complicated design of the 3rd gen galaxies factory air con-HVAC system. You have to wonder was this someone out of college having a go on design without empirical experience and really lost their way or the end result of some crazy higher up edict of management on part sourcing.

I love talking about esoteric items like this. I couldn't believe how expensive the AM-FM radio option was in 1968. Air con was usually the most expensive option. Here's an excerpt from Hemmings Muscle Car Magazine about a '68 LTD with a 428 and 4 speed manual. On the last page is the optional equipment and their cost. It's a fun read.

Cheers.

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