Reader Devin Vermeulen and I have been trying to figure this out this morning and I thought I’d pass it on to you while I deal with the 6,000+ scripted mails that Gmail won’t filter out for this TomTomGo contest. My guess was that something funky had gone sour in the Airport Express itself, because it doesn’t broadcast an FM signal at all, but transmits (or recieves, I guess) an encrypted data stream over Wi-Fi. It’s very peculiar. Feel free to send in your theories if you are an EE genius.
I recently bought an Apple Airport Express Base Station, and after installing it in my house, whenever I send music to it over the airtunes there is some FM radio interference on the signal- you can totally hear it under the itunes music being sent from my laptop but only when a song is playing on ituines. And it’s not interference from the receiver because I’ve tried to change the tuner dial and do it again but it constantly picks up the same bad r&b station (I haven’t yet figured out which one) Anyway- do you think it’s just some of New York’s over polluted wireless signals being so crazy that they’re infiltrating my wireless music stream or is there something I can do to fix this incredibly annoying situation. Let me tell you, when it’s 10am on a Saturday and all I want is some ambient electronica to slowly wake me, the sounds of “Little Lou Bega” fuzzily breaking in the background is far from the ideal situation I thought airtunes would bring me to.
I haven’t tried it with headphones further away from my living room, I should do that this evening. The thing is it didn’t happen for the first 2 weeks or so we had it and then all of a sudden it started. I was dumbfounded how it could be an FM signal of all noises. I hooked the extension cord from my powerbook to the unit so I could at least move it off the wall plug some distance but with only the 2 or 3 foot radius it made no difference whatsoever.
Update: Steve writes:
i suspect this has nothing to do with the wireless part of the airport/airtunes, but is more likely that something isn’t grounded properly in the electrical system at his house. generally speaking if that was the case it would happen all of the time (and not just when music is playing) but it could very well be that whatever chipset is being used is shutting off that signal path entirely unless it is in use. that would explain why it only happens when music is playing.
if it is due to a grounding issue then it would always be the same radio station (usually the strongest one in the area) regardless of what was playing, what outlet it was plugged into, etc. I have this problem myself on certain outlets.
if he doesn’t hear it through his stereo (he should trying turning it up all the way without anything playing to see if it’s there) then it could be specific to the outlet/circuit the airport is plugged into, and/or something could have changed (i.e. – maybe a refrigerator or something else is causing noise) or perhaps the airport is just more sensitive to RFI . he could do a variety of things to help resolve it, but assuming he doesn’t own the wiring probably the best thing to do is either get a special RFI/EMI filtering outlet and rewire wherever he puts the airport, or run it through a UPS or power conditioner (that way it will get converted to DC then back to AC cleanly).
power conditioning is always a good idea for any audio application, because even if it isn’t to a level where it’s noticeably degrading the sound quality, it is always present to some degree as part of the noise floor.
Ben Munson writes:
My conventional headphone extension cord running from my CPU to my stereo does the same thing. You do not need the Airport to create the problem. As far as I can tell, it has to do with the insulation of the cord itself running from the Airport/CPU to the stereo. I don’t hear it with other inputs, but I can hear it whether or not music is playing. He should try a new cord, different length cord, or something to change the linkage. The wire could also be picking it up from something else nearby.
Eric Bakken writes:
The cause of this is almost definatly the wires connecting the airport express to the stereo. I used to have a long stereo mini plug —-> RCA jacks going into my stereo from computer and the same thing would happen. The length and quality of the cord will make a difference. We are using a monster cable patch cord from the express to stereo and have no problems with interference. Spend good money on that stereo-mini plug to RCA inputs or use Apple’s other audio link cable, and the FM interference will disappear.
Jame Piggot writes:
In regards to your story “Airport Express Picking Up FM” — it’s not just him, and it’s not just New York. I live in Los Angeles, and the same thing happens to me; it’s drives me up the fucking wall. I finally figured out that it seems to pick up FM stations whenever it’s plugged into my A/V receiver, and when the USB cable connected to my printer is also plugged in. A weird combination of improperly shielded cables, maybe. But all I know is that I have to unplug my printer from the Airport Express everytime I want to use it to stream music, or I’m in for an afternoon of Korean religious radio.
Sounds like the cables should be shielded.
