In article , Dave Plowman (News)
wrote:
In article , Jim Lesurf
wrote:
So how does it filter/suppress the 19kHz pilot tone and the
remains of the 38kHz DSBSC after stereo demodulation?

Maybe like my old Quad FM3 tuner - don't bother to?

The diagram I have for the FM3 shows it using an MC1310 followed by a
pair of active LP filters. (The FM4 seems to use the Toko type '21
filter modules. But I don't know the filter shapes for these as they
don't give a part number I could trace to any of the Toko sheets I
have.)

My early FM3 caused real problems when recording to my A77. Had to fit a
filter to it.

I haven't analysed the filter but it doesn't have an obvious 19k 'trap'.
Just looks like a standard 3rd order LC design for a low pass. I'd expect
the 1310 to leak fair amounts of 19k, etc. That's why the 600s used a Toko
filter, and perhaps why the FM4 does as well!

Slainte,

Jim

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