Metals touching, produce EM waves

In summary, metal on metal noise was once a big problem for people like me that flew radio controller model aircraft. But nowadays radio control systems have much improved and I suspect are virtually immune.
  • #1
sv3ora
22
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Can you help me on this question I had for years?

Every time I touch two metals together (holding them with my fingers) and place a shortwave SSB radio nearby, I hear clicks and noises on the radio.
Why is that happenning?

Has anyone observed this phenomenon before?
 
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  • #2
Those sparks get in everywhere!
It strikes me that your two bits of metal (dissimilar?) are forming a simple electrolytic cell (battery) via the acid in the sweat of your hand. It the "bits of metal" are, in fact, wires then you would have the basis of an antenna, which would couple this energy into your receiver. If you are just describing the effect with two small metal items then it's a bit harder to understand how the dimensions can account for what you are hearing.
Give us a bit more detail, please.
 
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  • #3
There is another possibility, which I thought of whilst driving in the car this morning. If your wires are long, then they could be acting as receiving antennae and having an emf induced between them (or even some current from the mains). This can produce a spark when they are close enough, which will contain power at frequency that your receiver is tuned to.
 
  • #6
davenn said:
no, as there is no applied voltage
The Seebek effect is the 'opposite' to the Peltier effect. Seebek produces an emf due to temperature difference whilst Peltier produces a heat transfer due to an applied voltage. But I don't think the few mV per junction that Seebek can produce could produce enough emf for a spark. Plenty of current available to work a gas cutoff / flame detector solenoid, though, once you have a good contact.
 
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  • #7
Metal on metal noise was once a big problem for people like me that flew radio controller model aircraft. If vibration from the engine caused two bits of metal to rub together it could drive the radio control system nuts causing planes to crash. These days radio control systems have much improved and I suspect are virtually immune.

Edit: For info radios I used were typically 27MHz AM then 35MHz FM(PCM) and now they are 2.4GHz Spread Spectrum.
 
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  • #8
Well, the basic reason is that a current flows between the pieces of metal. The act of making contact creates tiny sparks that emit radio waves.
The current can come from several sources: Galvanic potentials, induced potentials from outside sources, including static electricity (as already mentioned).

You can test this by connecting the pieces of metal with a wire. Now you can make them touch all you want and no noise will be generated (except in very special cases)
 

1. How do metals touching produce EM waves?

When two metals come into contact with each other, electrons from one metal can transfer to the other metal. This creates a flow of charged particles, also known as an electric current. This current produces oscillating electric and magnetic fields, which combine to form electromagnetic (EM) waves.

2. What types of metals can produce EM waves when touching?

Any type of metal can produce EM waves when touching another metal, as long as there is a flow of electrons between the two. However, metals that are good conductors, such as copper and aluminum, are more likely to produce stronger EM waves due to their high number of free electrons.

3. Can metals produce EM waves when touching other materials?

Yes, metals can produce EM waves when touching other materials, as long as there is a flow of electrons between the metals and the other materials. This can occur with non-metallic materials such as glass, plastic, and even air.

4. Are EM waves produced every time metals touch?

No, EM waves are not always produced when metals touch. In order for EM waves to be produced, there must be a flow of charged particles between the metals. If the metals are not in direct contact or if there is an insulating barrier between them, EM waves will not be produced.

5. Can the strength of EM waves produced by metals touching be controlled?

Yes, the strength of EM waves produced by metals touching can be controlled by varying the amount of electric current flowing between the metals. This can be done by adjusting the voltage or resistance between the metals, or by changing the distance between them.

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