>> Choreboy wrote:
>>> Couldn't technology analogous to a megaphone be applied to dialup as >>> well as DSL?
>> Yes.
>>> Ah, crosstalk! It seems to me that if DSL uses the same wire dialup
>>> used, the same crosstalk will be present.
>> Not necessarily. Remember AM and FM radio waves go through the same
>> air, but AM is much more sensitive to lightning and other static than >> is FM.
>> DSL service may be arrangeed to minimize crosstalk.
> You've hit it on the head. Both AM and FM use radio bandwidth, but
> each uses a different form of modulation. AM stands for Amplitude
> Modulation -- the amplitude is how high a particular sine wave rises or
> falls. FM is frequency modulation, the carrier frequency varies
> depending on what signal is being fed to it.
Broadcast AM uses a channel 10 kHz wide. Broadcast FM mono uses 150 kHz.
It's sort of the same setup on DSL with the data signals occupying a > higher frequency.
Frequency shift keying and phase modulation could be called forms of FM. Modems have used them for decades.
I think dialups use a carrier of 2kHz or so. I think the baud rate is the samples per second. I think the 14.4k modem used 2400 baud with phase modulation so precise that each sample yielded 6 bits. Amazing! It's incredible that they found a way to get 56k out of a carrier somewhere around 2k.
Do you mean DSL has a much higher carrier frequency? I haven't found anything about it, but it could explain how it can carry 50 times more bits.