"Brenda Ann" wrote in message
...


Digital comms are purely square waves.

I'm using the term "square wave" to mean a sharp cornered pulse train
with an exactly 50% duty cycle. There's not much information there.
You've seen one pulse of the square wave, you've seen them all.


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.

And the square wave is recovered after only after demodulation of the
sine waves. The modulation doesn't necessaraly create harmonics, but it
does create sidebands.

This guy likes to use triangle waves in his illustrations:

http://www.cs.ucl.ac.uk/staff/S.Bhat...es/node12.html


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.

The carriers can be both amplitude and phase modulated to increase
bitrate.

Given that the BPL is usually described as a spread spectrum technology,
I'll assume there's many carrier frequencies.

I'm not sure how they do the band notching that
Japan tried before they tossed out the idea completely.




Doesn't Japan have a higher percentage of SWLs and radio amateurs than
the US? I don't think most Americans will much care about BPL unless it
effects the TV. I'll bet the BPL traps at 3.58 MHz work just fine.

Frank Dresser