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![]() "Frank Dresser" wrote in message ... "Telamon" wrote in message ... Data communications occupy wider bandwidths than the stated clock rate. It is not unreasonable to expect harmonics 3 to 5 times the clock rate because the signaling uses square waves and there is significant power in the odd harmonics. -- Telamon Ventura, California A square wave, itself, won't convey much information. It needs to be modulated, and the modulation would have to effect the symmetry and result in both odd and even harmonics. I don't know what sort of modulation BPL is using. I can imagine hundreds of low amplitude sine wave carriers from 2 to 60 Mhz, all of them phase modulated. In that case, I don't think there would be much harmonic output. Digital comms are purely square waves. The modulation is FSK or similar (generally)... in other words, the on-state is one frequency, the off state is another. This creates a chain of square waves which themselves are not modulated. The bandwidth, in this case 75 MHz, is how many on/off states there are in one second. This is also concurrent with bitrate. Compression schemes can raise the apparent bitrate, however the actual bitrate is the same as the frequency used. I'm not sure how they do the band notching that Japan tried before they tossed out the idea completely. |
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