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Good night, Since 2014 when I bought my car I use a FM transmitter inside it to play my bluetooth musics, to escape for every radio in city I put the radio to work in the highest frequency it works that is FM 107.90Mhz. A couple of years now I started to notice a very strong and loud interference and a white noise overlapping my music everytime I passed near every Gas Station. So Today I drove with 3 different radios in the same frequency 107.90FM and it happened in all my radios, those strong interference, only when I passed near the gas stations... So I googled it and find nothing about. What can be this strong interference on my radios in this frequency? I don't know where I could ask it, but I pretty sure it's physics area. The Gas stations doesn't have radio transmitters or antennas. Nothing near that could interfere with that weird loud white noise

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  • $\begingroup$ Not physics in the sense it is dealt with here. However you actually do not know if there are radios or transmitters in the gas station or near it. You are assuming that. There could also be other radio frequency equipment. Too many unknowns. $\endgroup$ – StephenG May 3 at 21:37
  • $\begingroup$ I went inside some gas stations that cause the noise, it's sure they don't have radio transmitters! It's a note of 5 years that I'm observing it $\endgroup$ – Victor Melo May 3 at 21:41
  • $\begingroup$ Victor, are the gas stations next to intersections with traffic signal lights at them? $\endgroup$ – niels nielsen May 4 at 4:57
  • $\begingroup$ No! I checked at least 30 differents gas stations around the city. I live in Brazil. And only gas stations cause it $\endgroup$ – Victor Melo May 5 at 2:56
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Possible sources of noise:

  • switching power supplies; modern switching transformers interrupt current with high frequency (kHz) to transform between high-low voltages; the rectangle-wave current makes the transformer radiate;
  • digital electronics and its wiring: computers, computer network wiring work close to MHz frequencies;
  • electric motors with brushes where sparks occur; arcs and sparks produce broad-spectrum radiation;
  • faulty isolation or otherwise faulty electrical equipment which makes electric arcs occur.

All these are likely to be present in a modern business building, including gas stations (pumps, computers, air conditioning system).

For more on the sources of EM noise, see for example

https://www.randombio.com/interference.html

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