Re: Water heater eating X-10 signal

["Jeff Volp" <JeffVolp@xxxxxxx>]

"Mr. Land" <graftonfot@xxxxxxxxx> wrote in message
news:1177822295.216764.266090@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> On Apr 27, 6:15 am, nob...@xxxxxxxxxxxx (Dave Houston) wrote:
>> "Mr. Land" <grafton...@xxxxxxxxx> wrote:
>> >I have a theoretical question for those of you with a lot of PLC
>> >experience: if I plug in some device known to eat X-10 signals, would
>> >I expect to see the same drop in signal level at all of the outlets on
>> >that phase?
>>
>> No. Signal sinks tend to be somewhat localized with outlets nearby or
>> downstream most affected.
>
> Huh.  That's interesting.  Obviously I'm no expert, but I would think
> that the (resistance/impedance) from outlet to outlet would be very
> low, so that anything sinking X-10 (or 110V, 60Hz for that matter)
> would be experienced at all the outlets on that circuit.

Electrical power distribution does provide low impedance for 60Hz.  However,
up at 120KHz things are a bit different.  Wire inductance and distributed
capacitance comes into play.  There is normally a steady decrease in signal
strength as the distance from the breaker panel increases.  Any "signal
sucker" will ramp the signal down more quickly on its circuit, and all
receptacles past that device will have a correspondingly lower signal level.

In addition to the steady decrease in signal strength as it moves away from
the panel, there can also be nodes and peaks if inductance and capacitance
just happen to hit a resonant point.  I believe that causes the "black
holes" that appear at certain locations.

Jeff