Hi!

I have an clock radio about 30 years old that, when tuning for 88.5
FM, for example, by turning the dial, will find that station, and then
a little higher will be another station, and a little higher still
will be 88.5 again, often a stronger signal than the first one.

If you're in the US, the low end of the FM band is used by public
radio operators. These stations may be low power or intended to serve
a large area (as is sometimes the case with public radio stations).
The station may in fact operate on multiple frequencies. They may
advertise this fact during station ID.

But sometimes strange things do happen. The other day I was listening
to the Delco AM/FM/Cassette radio in a 1988 Buick. This is a digitally
tuned radio or "ETR" in GM parlance. I bumped the tuning knob,
advancing the frequency from 99.1 to 99.7. Imagine my surprise when
the same station--with the same call sign and frequency announcement--
was found to be playing in perfect fidelity!

The surest thing to try is another radio, situated in another area
(another room ought to do).

And if you have one of those older Delco radios, here's something for
you to try one day if you're bored:

http://greyghost.mooo.com/delco/

William