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Sources of noise
Hello,
I'm interested in external Electromagnetic noise measurements taken out in the middle of the California or Arizona or Nevada desserts. Please note that I am not referring to hot-rock noise that comes from a metal detector transmitter. I'm gearing to head out to the desert in a few weeks to do some measurements but would appreciate as much data as possible. Basically I'll have an op-amp circuit with a bandpass filter hooked up to a multimeter-- nothing fancy, lol. So this is just signal receiving-- no transmitting. It's the external noise that is of interest. In other words, any noise except the noise that comes from your circuit. I understand that op-amps generate over 1nv/SqrtHz-- typically 5 to 15 nV/SqrtHz. Lets say you have a typical 16" coil. Does typical desert noise exceeds op-amp noise? How often is external noise lower than op-amp noise?
Frequencies of interest range from 500 Hz to 100,000 Hz. So the question is, where does the dominating noise in these desert areas come from and what's their strength? Any voltage levels, coil size, number of turns on coil would be great, but any data is appreciated even if it's your best guesstimate and you do not have any specific numbers. Do you think the noise came from below, above, north, south, east, west? Is it terrestrial noise or manmade noise? I'd presume that it is terrestrial noise. Although I'm not sure how much noise you would get from far away radio stations and power lines in the 500 to 100,000 Hz range. Perhaps there are underground power lines, but how common is that.
Here are some noise sources:
1. Atmospheric noise. This changes a great deal from day to night.
2. Galactic noise.
3. Thermal noise. Caused by vibrating electrons in all matter and covers the entire frequency spectrum.
4. Radio broadcasting. This includes everything from cell phones to radio stations to even household appliances. Of course this noise might be negligible out in the middle of the desert. I'm wondering on average just how close to a city one must get before this noise dominates.
5. 60 Hz Power lines.
6. Noise from vehicles such as cars, motorcycles, and planes.
7. Satellite noise.
8. Solar noise.
I'm thinking that #3, thermal noise, is extremely low. Obviously electronic components, with exception of perfect capacitors and inductors, possess thermal noise which covers the entire frequency spectrum. #3 thermal noise is mentioned because the vibrating electrons in the ground actually cause noise. Although I'm predicting that ground thermal noise is extremely low. The basic thermal noise power equation is (4 k T B).
I'm guessing that #4 radio broadcast noise is locatable by pointing the coil up toward the horizon and directed toward the source.
Thanks,
Paul
I'm interested in external Electromagnetic noise measurements taken out in the middle of the California or Arizona or Nevada desserts. Please note that I am not referring to hot-rock noise that comes from a metal detector transmitter. I'm gearing to head out to the desert in a few weeks to do some measurements but would appreciate as much data as possible. Basically I'll have an op-amp circuit with a bandpass filter hooked up to a multimeter-- nothing fancy, lol. So this is just signal receiving-- no transmitting. It's the external noise that is of interest. In other words, any noise except the noise that comes from your circuit. I understand that op-amps generate over 1nv/SqrtHz-- typically 5 to 15 nV/SqrtHz. Lets say you have a typical 16" coil. Does typical desert noise exceeds op-amp noise? How often is external noise lower than op-amp noise?
Frequencies of interest range from 500 Hz to 100,000 Hz. So the question is, where does the dominating noise in these desert areas come from and what's their strength? Any voltage levels, coil size, number of turns on coil would be great, but any data is appreciated even if it's your best guesstimate and you do not have any specific numbers. Do you think the noise came from below, above, north, south, east, west? Is it terrestrial noise or manmade noise? I'd presume that it is terrestrial noise. Although I'm not sure how much noise you would get from far away radio stations and power lines in the 500 to 100,000 Hz range. Perhaps there are underground power lines, but how common is that.
Here are some noise sources:
1. Atmospheric noise. This changes a great deal from day to night.
2. Galactic noise.
3. Thermal noise. Caused by vibrating electrons in all matter and covers the entire frequency spectrum.
4. Radio broadcasting. This includes everything from cell phones to radio stations to even household appliances. Of course this noise might be negligible out in the middle of the desert. I'm wondering on average just how close to a city one must get before this noise dominates.
5. 60 Hz Power lines.
6. Noise from vehicles such as cars, motorcycles, and planes.
7. Satellite noise.
8. Solar noise.
I'm thinking that #3, thermal noise, is extremely low. Obviously electronic components, with exception of perfect capacitors and inductors, possess thermal noise which covers the entire frequency spectrum. #3 thermal noise is mentioned because the vibrating electrons in the ground actually cause noise. Although I'm predicting that ground thermal noise is extremely low. The basic thermal noise power equation is (4 k T B).
I'm guessing that #4 radio broadcast noise is locatable by pointing the coil up toward the horizon and directed toward the source.
Thanks,
Paul
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