Re: Water heater eating X-10 signal

["Robert Green" <ROBERT_GREEN1963@xxxxxxxxx>]

"Dave Houston" <nobody@xxxxxxxxxxxx> wrote in message
news:4639b56e.164531546@xxxxxxxxxxxxxxxx
> "Robert Green" <ROBERT_GREEN1963@xxxxxxxxx> wrote:
>
> >What happens if you move the ESM1 meter head near the transformer, as in
> >mounting both the head and a power supply inside the same box and having
> >just a line cord extend from the unit?
>
> >What would happen if I recorded in MP3 and converted back to WAV format?
> >would the loss be noticeable?  Disk space wouldn't be as much of an issue
> >that way.
>
> I tested the effects of the wall transformer on the meter extensively when
> the ESM1 was introduced (and my review here savagely attacked on those
very
> grounds). I found no effect. My test setup usually has the wall
transformer
> in a powerstrip on a work bench with the meter sitting atop the
transformer
> and my Scope-Test2 or other filter plugged into the same powerstrip.

That's good to know.  If it all works out, I will remount everything in a
different case with a single, very long line cord.

> I have no idea how lossy MP3 might be in this case. I use Loop Recorder
for
> tests like these and it only records .WAV files. All I can suggest is that
> you experiment.
>
> Until I test it I don't know whether the soundcard will record the higher
> frequencies that are beyond the audio range. Since we're sampling at a
rate
> well below the Nyquist limit, we'll see an aliased noise signal if it's
not
> filtered out first. My Audigy soundcard can sample at 96Kb/s (although
Loop
> Recorder does not go that high) but higher frequencies may be filtered
> before the sample is taken. This is, after all, a $1.98 solution (1 audio
> cable, 2 resistors) which, while it may not be the ultimate piece of PLC
> test gear for all conditions, it should prove useful to anyone who already
> has the ESM1.

I see.  IIUC, the X-10 signal's frequency (120KHz?) is way outside the
normal audio range so eventual success is going to depend a lot on the
characteristics of the sound card and recording software.  Are there any
electronic tricks that can bring the frequency down?  Halving the playback
speed would reduce the frequency of a normal audio signal but that wouldn't
work here because the card may not be able to capture the higher frequency
to begin with.  No magic frequency divider in a IC package or does that mean
lots of additional support circuitry and isolation issues?

--
Bobby G.