I am working on a system which should communicate with a ~100kHz signal, and read that low frequency channels, e.g 10kHz to 200kHz, are especially susceptible to interference.
Why is that? Are they more susceptible than say a 500Hz signal?
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If one is trying to send a 10kbit/second data stream modulated at 910.0MHz, the information for every bit of data will be spread out over 91,000 cycle. By contrast, if one were trying to send a 1kbit/second data stream modulated at 100kHz, each bit of data would be spread out over only 10 cycles. A lot of radio interference comes from events like the closing and opening of switches that start and stop significant currents. Each such event may be modeled as clobbering a cycle's worth of communication on all frequencies. At 910MHz, an event which clobbers one cycle's worth of communication would probably go unnoticed, but at 100kHz, it's far more significant. It wouldn't take very many such events happening close together to disrupt a bit on a 100kHz-modulated data stream.
Higher frequencies allow for more robust modulation techniques. Eg. frequency modulation is a lot less susceptible to noise than amplitude modulation or no modulation at all. The downside of FM modulation with regard to AM modulation is the increased bandwidth required.
In amplitude modulation or when using no modulation at all, the information is stored in the amplitude of the signal. Interference will introduce variations in amplitude, like spikes, which in turn will be in the received signal.
Higher frequencies tend to use (some sort of) frequency modulation. With FM no information is stored in the amplitude of the signal; all information is stored in the frequency of the carrier wave. When interference is picked up, it may introduce variations in amplitude, but these variations will be discarded by the receiver anyway. The noise introduced on the carrier wave frequency can easily be removed by the receiver, because the receiver can tightly track the carrier wave and disregard changes to it that are too fast to be correct.