John Smith I wrote:

Digital is not analog, when adverse conditions have made an analog
signal totally unusable, a digital signal, most likely, may still be
achieving 100% error free data transfer--it is just the nature of the
beast.

Hi John,

The error here is that that digital signal in a bpl setting is trying
to function in an analog world. And for all practical purposes, while it
is on the line and till it hits the modem, it is just another RF signal.
Disregard the 1 and 0 aspect, and think about the rapid stream of
pulses. Each one on it's own is just a "state of 1 or 0, but taken
together, they are pulses that occur at RF frequencies in toto.

So here you have a string of pulses that are running at say 10 MHz. If
no other signal gets into that line, all is well. But that same line,
which can inadvertently radiate outward, can pick up another signal on
the same frequency - and it is very likely that whatever frequency you
might be transmitting on will affect it, since the pulsed frequency
equivalent (sorry for the goofy term, I'm not sure what else to call it)
varies by quite a bit, thereby making it vulnerable to lots of different
frequencies being transmitted.

Then if say the local school bus company is transmitting on some
frequency near the BPL line, that power line might pick up some of that
transmission, and send it down the line into someone's modem. That modem
won't be able to make any sense of the messed up packets it is
receiving. It'll call for a resend, and receive more gibberish.


The "intelligence" of the software controlling the data transmission(s)
is the single most important factor--as logic would dictate. Even under
almost total saturation (it would be virtually impossible for 100%
saturation, baring hooking the kw+ rig directly to the power lines) of
the BPL signal some type of heterodyne would be occurring with the KW
signal.


A packet is a surprisingly delicate thing. It takes nowhere near
hypothetical 100 percent saturation with an RF signal to change one bit,
which can disrupt a packet.


Digital is magnitudes more robust than analog, again owing to the very
nature of the beast and the simplicity of the on/off, pulse width,
timing nature of the signal.

John I might respectfully suggest that you do a little studying on the
nature of digital signals. I've been dealing with them since the late
70's, and they aren't anywhere near as robust as you believe.

- 73 de Mike KB3EIA -