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From: Jeff Liebermann on 15 Mar 2010 18:19
On Mon, 15 Mar 2010 17:17:14 -0400, mm <NOPSAMmm2005(a)bigfoot.com>
wrote:

>I have an clock radio about 30 years old

Any particular maker and model?

>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'm not so sure. Get the call letters for each station when they ID.
My guess(tm) is that it's an FM translator or booster:
<http://www.fcc.gov/mb/audio/translator.html>
We have a local religious station that can be heard on multiple FM
band frequencies. All of them are translators.

--
Jeff Liebermann jeffl(a)cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
From: Robert Macy on 15 Mar 2010 18:27
On Mar 15, 2:17 pm, mm <NOPSAMmm2...(a)bigfoot.com> 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?

Old radio? I had that happen once when the tuning control was
nonlinear. Actually passed over the same tuning points multiple time.
Did happen only at the ends of the band, too.
From: Allodoxaphobia on 15 Mar 2010 18:29
On Mon, 15 Mar 2010 17:17:14 -0400, 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.

Well, at 30 years, it sure ain't digitally tuned!

The variable capacitor that you tune the radio with is going to full
capacitance (lowest frequency) _before_ it reaches the physical stop.
Ergo, once you go past full capacitance and approach the physical stop,
you will be tuning back _up_ in frequency again -- all be it for just
a short range...

Too, with the age of the radio, 'things' have changed and undoubtedly
the alignment has shifted to exacerbate the effect you see.

Jonesy
--
Marvin L Jones | jonz | W3DHJ | linux
38.24N 104.55W | @ config.com | Jonesy | OS/2
* Killfiling google & XXXXbanter.com: jonz.net/ng.htm
From: PeterD on 15 Mar 2010 19:38
On Mon, 15 Mar 2010 17:17:14 -0400, mm <NOPSAMmm2005(a)bigfoot.com>
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.
>

NPR stations are well known for playing the same programming relayed
from station to station.
From: William R. Walsh on 15 Mar 2010 19:52
Hi!

> I had 3 GM cars in a row, and I'd like to get back to GM. I heard
> about some GM convertible last week and googled for it, only to find
> out it's a Pontiac, which afaik, they don't make any more.

Pontiac is winding down through 2010. Their cars will be available for a
while yet.

> I'll be looking for a car about 5 to 7 years old, and I'm glad to know
> about this because 4 presets really isn't enough.

By that point, the GM radios didn't do that any more. I reckon the last ones
to support it would been sold sometime in the mid-90s, when that particular
style (did you visit the page?) finally faded away. It would have been a
very old design at that time!

These weren't bad radios though. The tuner is pretty good (although it's
quite sensitive to antenna placement), FM stereo separation is *excellent*
and the audio section doesn't lack power output. With the bass slider all
the way up, these things sound like they are driving a subwoofer, and they
will shake the rearview mirror. (!!!) Delco Electronics could build a good
radio when they wanted to.

> (Chrysler has 10 AM and 10 FM. Last I checked for the 80 to 95
> cars, Chrysler had 3 companies making them at one time or
> another, or maybe even simultaneiously, even though they all
> looked alike.)

The two sources I've seen radios from were Mitsubishi and Chrysler
themselves. It seems that Chrysler had some electronics production
facilities of their own, mostly used for the simpler (AM, AM/FM and
AM/FM/Tape) radios.

William


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