In article ,
mm wrote:

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.

I'm sure it's not a second station playing the same stuff.

I know about harmonics on AM MW and Short Wave, but here the tuned
frequencies are so close, and also I didn't think there was stuff like
this involving FM. What is going on?

MM-

See if you can determine the frequency of the second station that
appears to lie between the two occurrences of 88.5.

My guess is it your radio's tuner reaches its minimum frequency before
the end of rotation. Turning it further starts to increase frequency
again until it reaches its end of rotation. The second station is so
close to the minimum frequency that you can't tell if it appears twice
or not.

It is a mechanical effect that I've seen in both capacitor tuned and
inductor tuned systems. The capacitor is fully meshed before it reaches
a stop. The inductor core passes the center of the coil before it
reaches a stop.

Fred