On Mon, 15 Mar 2010 14:45:05 -0700 (PDT), "William R. Walsh"
wrote:

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).

That's right. This is 88.5, WAMU, American University in Washington,
DC, an NPR station. I'm in Baltimore 35 miles north of DC (though I'm
not sure where the antenna is) and it comes in well almost everywhere
in Baltimore and 20 or 30 miles or more north of here.

The station may in fact operate on multiple frequencies. They may
advertise this fact during station ID.

I've been listening for 10 years. Never any reference to that. In fact
88.1 is a Balt. NPR station, and 88.3 is something else. Also not
much in the way of hills around here, until 50 or 60 miles west

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