AM Radio Interference: FAQs & Solutions

[ChromeBit]

Hi,
I'm interested in AM radio transmissions causing interference (not just noise, but the transmission actually being demodulated by the speaker and leaking into the amplifier circuit) in devices such as unshielded speakers (that are not designed to work with radio). I'm currently having issues with a CB or HAM radio enthusiast nearby and I'm trying to work out a couple of things.

1. What is the lowest amount of power someone would need to be using to generate audible interference, especially if they are quite close to my speakers? (Could this person still be transmitting on the legal levels?)
2. Is this interference more likely to happen at a specific frequency, such as either a CB or HAM frequency?
3. How does the signal get demodulated by my speakers? (I know that extremely simple crystal radios use just a diode)
4. Is there anything I can do at my end to stop the interference?
5. I've heard people suggest his/her equipment might be faulty (or modified), why might modified/faulty equipment cause this interference more readily?

 

[nsaspook]

Drop a note to the person causing the interference, if it's a licensed operator they should be glad to help.

The simple solution at your end is adding RF chokes to the signal and power lines of the effected equipment to stop the RF signal from entering and being demodulated by some non-linear process.

http://audiosystemsgroup.com/SAC0305Ferrites.pdf

 

[kyaw ye yint]

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