It's not overly amazing that particularly simple radios aren't overly
impressive on FM; my ICF-7601 is an example for such a design: After an
antenna matching circuit, signals are fed directly to an IC that does
mixing to 10.7 MHz, has stuff filtered by a single IF filter (280 kHz or
whatnot) and then demodulates it with the help of a 2nd filter for
discrimination. The sensitivity to overload depends entirely on the IC
used, and with only one filter, selectivity isn't great.

The ICF-SW7600G(R) already uses a better design with an FM pre-amp and
two cascaded filters (though both are still rather wide at a spec'd 280
kHz). It can still overload quite a bit (that's the downside of the
rather good sensitivity), but fitting narrower filters (I had mine
changed to 110 and 150 kHz parts, respectively) improves selectivity
significantly, allowing some DX. (Same goes for the ATS-909, which,
modified with two 110 kHz filters, seems to be quite a popular choice
among FM DXers here.) I can only recommend such a modification if you're
regularly using the FM part. (The YB-400 apparently uses better filters
out of the box.)

Grundig's Satellits, BTW, used three cascaded FM IF filters. (The old
Sony ICF-5900 - along with the older ICF-5500 - also did, but these were
rather wide at - guess what - 280 kHz.)

For top performance, nothing beats a bunch of cascaded filters and
discrete components, of course. High-end FM tuners use(d) as much as
four cascaded filters.

Stephan
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