Can hear neighbour's cell phone ringing...

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Yonatan
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Post by Yonatan »

I can hear my neighbour's cell phone ringing through my amp when using my circuits. Is this RF interference, and how can I prevent it? Capacitor to ground on the input? Resistor on the input (in audio path? to ground?). Or is this a problem of enclosure shielding? (I have one circuit built into an enclosure, and one circuit sitting on the breadboard, but they both have this problem.)

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jmraney317
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Post by jmraney317 »

Yes, that is exactly what you're getting. The solution, though, is going to depend on first finding which part of your rig is acting as an antenna. Since you have something on a breadboard, try adding a small (47 pF or so) capacitor from the output of your breadboard circuit to its ground and see if that helps.

If not, you may need to try the same thing across the input jack of your amplifier. If that doesn't solve the problem, the problem would have to be somewhere inside your amp. (You are using a three-prong plug, aren't you?)

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Yonatan
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Post by Yonatan »

Just to follow up, for the circuit in the enclosure, this was solved as far as I can tell by putting the back on the enclosure :)

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RnFR
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Post by RnFR »

the remedy for RF interference is a small series resistor and cap to ground (LPF) on the INPUT. you want to filter it out before it is amplified, not after. on the upside, you may get to spy on your neighbors phone calls.
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