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Cell Phone Noise in FM Transmitter Answered

I have recently built a dock for my HTC touch for use in my car. The dock is basically a holder with a cheap FM transmitter in the back. The FM Transmitter and cell phone are connected in parallel to a 5 volt USB car charger. For some reason, the FM transmitter is picking up noise from the cell phone. It is digital noise, different frequencies and beeps that vary depending on what I am doing on the phone. The noise is very quiet, but still there. Is there any simple solution to filtering out this noise? Will a simple capacitor do? Thanks Andrew

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BrianKT (author)2009-06-07

I am assuming you are using your HTC Touch on AT&T or T-mobile. These are GSM networks. That beeping is called GSM buzz . To fix it you can use ferrite beads. http://www.maclife.com/article/iphone_buzz_kill

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computerwiz_222 (author)2009-06-07

Yeah I get that too - I listen to streaming radio on my data plan, and i get a steady "purring" sound. Whenever data is transferred between the phone and the tower, or between the phone and itself, it makes a noise in the transmitter.

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lemonie (author)2009-06-07

I picked up a taxi on an old stereo once, made me jump. Some kind of shielding perhaps? L

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NachoMahma (author)2009-06-07

. Electrical filtering may or may not work. If my cell phone is within about 2 meters of my computer, I can hear when it pings the tower.

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