In article ,
"Frank Dresser" wrote:

"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. This would certainly still be a big problem for the
radio hobbyist, but not so much for the FM/TV user. There have been
several BPL tests in various communities, and it doesn't seem to have
wiped out normal broadcast use.

If BPL caused enough bothersome interference to keep people in the test
communities from their TVs and radios, the National Association of
Broadcasters would have squashed it like a bug.


It is a common error to assume that digital communications are similar
to analog RF. One reason is very fast edge times are required to create
the most eye margin possible at the decoding end of a data stream so the
bandwidth required is much greater. A good rule of thumb is 3.7 times
the clock rate as a minimum. Usually the engineering shoots for the
fastest edge times practical.

An one/zero pattern and multiples thereof are square waves but I should
not have used that term because it looks like I just threw you off the
path of understanding.

--
Telamon
Ventura, California