Radio Stations, what is their source?

What format do Radio Stations use for a source? I have been told MP3, then I heard a DJ mention he downloaded a certain remix from the 'net that he played, leaving me to believe they do use MP3.
Here in Portland, OR our public stations use all sources, MP3, casette, CD and, you can tell by the scratches, LPs. Interestingly, they also do a number of live broadcasts. Are you aware that a live radio broadcast is the only source available to most home systems that is not subjected to any form of storage media? Playing back one of these broadcasts on an excellent tuner rivals, and sometimes exceeds the finest CDs and LPs.

Thats an interesting statement considering fm doesn't broadcast the full audio spectrum 20-20khz. 20-15khz if I'm not mistaken
Also add minidisc, CD-R and dedicated hard disk systems.
As we all know, frequency response, particularly at the extremes, is hardly the primary arbiter of sound quality in reproduced sound. If it was, all we would need is wide bandwidth components and equilizers. The "full spectrum 20-20k" is rather arbitrary at that. There is good evidence that we have a response to sound well above and below the specified frequencies. To complicate matters further, there are beats, or difference frequencies, that result from constructive and destructive interference within sound waves. A 22K and 23K tone, under the right circumstances, can produce a product at 1K, well within the audible range. By that thinking, the LP, with response out to at least 50K, would automatically qualify as a higher fidelity medium than redbook CD, which is already rolling off at 20K, and many of us think that it is. But even the staunchest defenders of the LP medium would admit that other factors such as surface noise partially mitigate the advantages of the format. Oh, and FM frequency response is generall given as 30-15K.
The only station I listen to plays pretty much everything and anything as far as format(classical music only) goes and that includes a fair amount of LP's- its nice to hear a little hiss and pop coming from the radio :) They also do this program once a day called Performance today where they get a live performance some where and air it- often it takes place in the studio.
FM is 50-15kHz. AM is around a telephone land line. Open E on a 4 string bass guitar is around 40Hz.

Unless you are a 16 yr old female, try a test tone CD, like the Rives Audio or equivalent, and see if you *really have anything going on above around 10-15kHz. It will really open your eyes(ears).