j.hall wrote on Thu, 13 May 2004 16:01 |
WOW.....
that is the answer i'm looking for
help me out a little more if you don't mind
i only get that noise when my phone is actually ringing, it's not constant durring the ringing process
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You'll get the noise when the phone is about to ring, ringing, or perhaps while it's idle "calling" the tower. I have never heard a noise like this from my phone while it's operating (talking). My guess is because the noise is actually caused because of a transitional state that the phone cycles in and out of during ringing and tower comm.
Look at it like this. As you know, when discharged with no voltage across it, a capacitor is a short circuit. When a change in voltage across the capacitor occurs, then current flows through the capacitor until it becomes charged, at which point current won't flow any longer. This is by definition a transient current. If it's AC, then current will flow the other way when the waveform polarity changes, etc. But with DC, like the voltage running your cell phone, the cap charges up and then current only flows if it discharges.
The decoupling caps, filter caps and all that on the DC line will do this when you turn a DC circuit from "off" to "on". So when your cell phone is sitting there doing nothing, the circuitry that's there to ring the phone is "off". It's in standby, some other state of low-current, or maybe in reset or powered off. Phones are designed to conserve power. When it rings, this circuit is turned on, and there is a spike in current flow which is the very definition of what causes an H field to occur, change in state of current flow. When it goes off, then the capacitors and other things discharge (another current spike, opposite polarity), then if it comes back on, another current spike, etc. This is what's causing the noise, methinks. Not for sure, but an educated guess. If you hear the noise BEFORE the phone rings, this is the cause. If you hear the noise occasionally when the phone is idle, this is the cause.
The vibrator in the phone is an electromechanical transducer like a speaker (actually it's like a solenoid). It will DEFINITELY make a cyclic magnetic field. If you only hear the nosie while it's actually ringing (vibrating), then turning off the vibrator in the phone might alleviate the problem.
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my phone is most commonly set to vibrate only, sometime ring and vibrate simultaneously....
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Try setting it to ring only and see if it helps. IMHO it might. If it were a Sony-Ericsson phone, I'd think it wouldn't help.
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is this a shielding issue?
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No. Shielding does not work on magnetic fields, unless you use a high permeability material like mu metal (very expensive, not likely you can use it). You could shield the phone with mu metal and it might work, but it would be very hard to use the display, hear a conversation, or push a button
. Maybe you need a mu-metal holster for it
Your shielding is used for other things (notably, it's really used to improve grounding, but I don't want to get back into that debate).