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Hot answers tagged signal-identification

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If you approximate the yellow trace as a rectangular function: $$\text{rect}(ax)$$ then the Fourier transform of this is: $${1 \over |a|} \cdot \text{sinc}\left(\xi \over a\right )$$ Of course, a lightning impulse isn't exactly a rectangular pulse, but I suspect that does not substantially change the character of the frequency response: infinite, with ...

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You have to provide the -i option to invert the signal in order to decode it properly. The lowpass filter is not really required as this is a quite strong signal (but does not harm either). \$ ./rs41ptu -i --crc -vx wav/20140717_402MHz.wav sample_rate: 48000 bits : 8 channels : 1 samples/bit: 10.00 [ 5047] (K1930308) Do 2014-07-17 12:32:13.999 lat: ...

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There's multiple way that multiple signals can be sent at the same time on the same frequency. One is to have multiple antennas, where even though the antennas themselves can be omnidirectional, they can be used to "beam form" by carefully offsetting the signal. And likewise the receiver can do this trick. Also see this article on MIMO. Wifi can ...

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Transmission between antennas is "two port in to two port out". But: in between there is a transmission path with reflections. Some frequencies are attenuated and some other frequencies are even stronger than average. That is called Rayleigh path (sorry, not complete for the moment). The transfer is frequency-dependent AND antenna position ...

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From the wide spectrum screenshot it's evident your receiver is seriously overloaded. Note: the signal around 445.982 which appears to be identical other than being "flipped", and a little stronger. This comes from IQ imbalance in the receiver. additional copies of the signal all over the place. These are caused by intermodulation and harmonic ...

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A Wi-Fi transmitter, like a lightbulb, throws out photons in a lot of directions. Only some of them will be captured by the receiver. Most will go elsewhere, eventually being absorbed by walls, atmospheric water vapor, and so on to be converted to heat. The Friis transmission equation explains this in more rigorous terms. Even if the two antennas are ...

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Yes, multiple signals can exist on the same frequency at once. In a net, this could happen if two people tried to talk at the same time. This is called a "double". When this happens, the signals mix, or add together. If the two signals are AM, the amplitudes of the radio waves add, which corresponds to the amplitudes of the audio, so you get ...

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First, the router power will be +20 or +22 dBm. Subtract a few dB on the way to the antenna, more if it's an internal antenna. Second, the free space path loss will be at least 20 dB, from phone to router, a few cm apart. This means that even held close by, the phone antenna only captures 1% of the transmitted signal. This will be made worse by the ...

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