Timeline for Why does an MRI machine or other EMP generating machine not damage humans, but it will fry computers?
Current License: CC BY-SA 4.0
11 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| May 8, 2023 at 21:20 | comment | added | The Guy with The Hat | @JohnDoty To add another anecdote, I once made a breadboard circuit that IIRC was intended to be a simple mic -> speaker amplifier. I discovered that when I touched the metal top of one of the capacitors, I could make out voices from a nearby radio station. I assume that this was my body acting as an antenna. | |
| May 7, 2023 at 12:39 | comment | added | John Doty | @ShoulO On a circuit board, the wires are surrounded by insulation. Nerves are surrounded by conductive salt water. | |
| May 7, 2023 at 9:53 | comment | added | Therac | @JohnDoty That should have been the plot of the new Matrix.... Machines have run out of good antennas and now need humans to hold their rabbit ears. | |
| May 6, 2023 at 14:34 | comment | added | ShoulO | that is what my question is about. It looks to me that human body is packed with 'wires' - i.e. nerves | |
| May 5, 2023 at 21:37 | comment | added | John Doty | @hyportnex Below 1 MHz, you're right. Even at 30 MHz, atmospheric noise is still pretty high. But things are get quieter above 100 MHz, and a human body is a decent size for that. Of course, its conductivity isn't great, and it won't work at high power. RF burns are a thing... | |
| May 5, 2023 at 21:20 | comment | added | hyportnex | @JohnDoty the reason for the transmit application is that the receiver CNR below 1MHz is limited by external atmospheric and man-made interference and not by front-end amplifier's thermal noise, hence the size of the receive antenna is almost irrelevant to the receiver's quality but not so the transmit power: the bigger the transmit antenna the higher the CNR. | |
| May 5, 2023 at 21:13 | comment | added | John Doty | @hyportnex hah ツ | |
| May 5, 2023 at 21:11 | comment | added | hyportnex | @JohnDoty actually I remember being the youngest in the family always to get that damned assignment to be holding on to the rabbit ears. Anyhow, I meant to say not any kind but specifically "transmitting antennas". I think you agree that kind of application would be a bit unusual for a human body... | |
| May 5, 2023 at 21:02 | comment | added | John Doty | @hyportnex "humans have not been used as antennas". You must be too young to remember how the "rabbit ears" on VHF televisions sometimes worked much better with somebody touching one of them ツ | |
| May 5, 2023 at 20:18 | comment | added | hyportnex | "There aren't any wires like that in our bodies." this is not quite true. Our whole body is not a bad electric conductor. While humans have not been used as antennas, there have been experiments to use trees in a dense forest as HF, below 100kHz, antennas. It can work because the tree juices are not too bad conductors. You run a few loops around the tree as a kind of magnetic coupling to induce the currents. | |
| May 5, 2023 at 19:40 | history | answered | Solomon Slow | CC BY-SA 4.0 |