Does FM radio shift frequency over long distance?

[Sukhoi]

I have a digital tuner radio that I am going to assume is accurate (no problems with any other stations). Just moved a couple weeks ago, and now I am receiving a station on 94.6 that verbally says they are 94.7, yet if I tune to 94.7 I get a completely different station. What gives? The station is something like 60 miles away, so is the wavelength somehow increasing across the distance?

 

[SecurityTheatre]

FM doesn't shift frequency over distance. Temperature and a few other things can affect frequency, though.

As an example, the shift in frequency of EM radiation from stars (some at the radio frequency) can be accurately used to measure the relative speed of the object over interstellar distances.

 

[DrPizza]

FM doesn't shift frequency over distance. Temperature and a few other things can affect frequency, though.

As an example, the shift in frequency of EM radiation from stars (some at the radio frequency) can be accurately used to measure the relative speed of the object over interstellar distances.

How would temperature affect frequency?

 

[Modelworks]

Sounds like adjacent channel issues. It used to be the rule that channels had to be .5 Mhz steps apart but as the airwaves got more crowded that was relaxed. If two stations are very close to each other they can easily confuse a receiver enough that it might display it is one station but internally the PLL is having problems locking on to the specific station because they are so close. Older digital receivers have a problem with newer broadcast because the accuracy they were designed with expects .5Mhz separations, not .2Mhz like some stations use now.

Depending on the path from the transmitter to the receiver you can have all sorts of weird things taking place. For example a signal at 96MHz may interfere with a nearby 97 MHz signal if the 97 MHz signal bounces around enough to alter its strength, the receiver will lock onto the 97 MHz signal and try to use the AGC to increase the gain, which will increase the 96 MHz signal and now you have 96 MHz output on a 97 MHz setting. All depends on how good the receiver is that is in use and how accurately it filters adjacent channels.

 

[SecurityTheatre]

How would temperature affect frequency?

I guess I was talking about the temperature of the receivers or transmitters. The electronics themselves are often temperature sensitive. Both oscillators and PLL circuits in receivers can be sensitive to that.

Of course, strong temperature gradients can affect EM radiation as well, but not significantly enough to be noticeable in this scenario.

 

[William Gaatjes]

FM doesn't shift frequency over distance. Temperature and a few other things can affect frequency, though.

As an example, the shift in frequency of EM radiation from stars (some at the radio frequency) can be accurately used to measure the relative speed of the object over interstellar distances.

I may be mistaken, but i remember that a blue shift or red shift can occur because of the movement. But since the composition of stars can be predicted with a reasonable accuracy, the redshift or blue shift is accounted for. Indeed you are right, because the redshift or blue shift is used to determine the speed of the object. Just as the Doppler effect if i recall correctly.

For those interested :
A star made up primarily from hydrogen, will radiate EM at a specific known wavelength. The deviation of this wavelength because of redshift or blueshift is used to determine the speed.
Of course, gravitational effects are evened out. Or in some occasions used as a means to discover interesting phenomena in space.

http://en.wikipedia.org/wiki/Hydrogen_line


EDIT:
Of course there are interesting theories with accompanying research that we might be off in some occasions when it comes to using hydrogen spectral lines to determine distances and dimensions in the universe.

 

[Sukhoi]

Interesting stuff!

 

[Dude111]

1 time this FM station was drifting like crazy (Remote repeater -- No one @ that bldg) -- They were making a mess on the dial!!!!

I called this guy i know who works @ the main station and told him and they got it fixed (Happend a couple times) -- NOT G00D TO BE DRIFTING OVER OVER LEGIT STATIONS!!