I have a gizmo for the car that plugs into my iPod and broadcasts it on any FM frequency you select. I found a frequency that sounded as much like white noise as I could find. It sounds great sitting in the driveway. But I’m a little disappointed–as I make my way 30 miles around the Beltway to go work, there are lots pockets of static inteference, which makes listening to my iPod similar to listening to a radio station with a weak signal. Which leaves me with a couple of questions.
How can random radio noise be stronger than a signal originating inches away from the radio? Is my transmitter underpowered?
Is this really random noise or is it possible that something is actually transmitting noise on that frequency?
Of course your transmitter is underpowered.
The FCC has allocated a specific frequency range for radio stations to broadcast music and voice on, using FM modulation. As far as the FCC is concerned, those guys are the only folks who should be using those frequencies.
So here you come along with a device that effectively turns your ipod into its own little broadcasting radio station. As long as its not powerful enough to effect anything outside of your car, the FCC isn’t going to care too much. But, if your device is powerful enough to cause interference to the guy next to you who is trying to listen to the radio station that actually paid a licence fee to use that frequency, then the FCC is going to get really pissed.
So, of course the manufacturers of these FM modulators keep the transmitting power down to an absolute minimum.
Those devices work fairly well in rural areas where you can find frequencies that no one is using. They don’t work so well around the DC beltway (which is the beltway that I am assuming you are referring to, since your location is given as northern VA). There are just too many radio transmitters in the DC area. It’s giong to be very difficult for you to find a clear frequency for your ipod to broadcast on.
If you get a car stereo with a line level input you can just plug your ipod directly into that and avoid all of the hassles and interference.
It may be inches away from the radio, but where is the receiving antenna?
Get one of these kits.
I can pick up my home MP3 jukebox a block away from my house using my car radio 
But that’s the part I don’t get. I am not getting signal inteference, I am getting noise interference. I am not hearing any radio station broadcast breaking in, just random static. Why isn’t the transmitter strong enough to at least blot out ambient noise?
Well, that could be a discussion unto itself. The answer is about 2-3 feet. But the radio works pretty well even if I remove the antenna, which I discovered once at the car wash. Maybe the cable from the external antenna to the radio is part of the antenna system; I know next to nothing about radios.