Re: Justify Upgrade from X-10 to Z-Wave?

["Robert Green" <ROBERT_GREEN1963@xxxxxxxxx>]

"Jeff Volp" <JeffVolp@xxxxxxx> wrote in message
news:Kb79k.77043$102.32851@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> "Robert Green" <ROBERT_GREEN1963@xxxxxxxxx> wrote in message

<stuff snipped>

> Good question.  Actually I have that situation here all the time.  When
I'm
> testing XTBs in my lab, my "home" XTB-IIR does participate too.  Since the
> 120KHz is created locally at each transmitter, the frequencies will differ
> slightly.  The actual voltage at any given point is the vector sum of both
> signals.  The original transmitter will obviously dominate the local
> circuit.  Since the XTB-IIR should have the lowest impedance coupling to
the
> distribution panel, its signal should dominate for the remainder of the
> home.

I hooked up the Monterey PLSA behind an AF120 15A filter and got some
interesting readings.  The WGL received an RF command and put it through a
TW523 onto the house wiring.  The Monterey showed normal commands being
received (at .15 volts, even behind the filter!) with one exception:  The
display showed them all in lower case, which means it only saw the second,
repeated half of the command.  That makes perfect sense.  The II is stronger
than the original XTB and the XTB/TW523 combo was on another circuit.  Only
the repeated signal could punch through the filter, as would be expected.

The next test is to see whether the WGL's TW-523 alone gives the same
readings.  If it's higher without the XTB, then there's cancellation going
on.  If it's higher *with* the XTB then the two signals are combining.
IIRC, the IIR alone can't punch through the AF120.  The fact that is does so
when it's amplifying an already boosted signal from the XTB seems to
indicate that the end voltage of an XTB that's repeated by the XTB-IIR is
considerably higher than either unit alone.

I tried doing some "signal dissect" runs where the Monterey looks at each of
the 22 cycles and records 0's and 1's and their voltage during each cycle
and that gave me information that seems to imply cancellation is occurring.

Cycle
01        1    .42      1  .43
02        1    .39      0  03m
03        0    02m    1   .42
04        1    .38      0   03m
05        1    .38      0   02m
06        0    02m    1    .41
07        0    02m    1    .41
08        0    02m    1    .41
09        1    .37      0    03m
10        1    .37      0    03m
11        1    .38      0    02m
12        1    .25      1    .24
13        1    .22      0    03m
14        0    03m    1    .22
15        1    .21      0    03m
16        1    .20      0    03m
17        0    03m    1    .20
18        0    02m    1    .19
19        0    02m    1    .19
20        1    .18      0    03m
21        1    .18      0    02m
22        1    .17      0    03m

Now that I've transcribed that lengthy list two things seem to jump out.
First, the noise level is very low, probably the result of the Monterey
sitting behind the AF120 filter.  The second is that the repeated frame is
seems to be actually weaker than the first copy of the X-10 command.

Obviously I need to run more tests with both the XTB and the XTB-IIR but it
looks like we're seeing some fade in the voltage as the command progresses.
Looks fairly linear, too.

> For the techies out there - it is feasible for null points to exist where
> the two signals will exactly cancel.  However, that would mean both
signals
> are identically strong at that point, and are exactly opposite in 120KHz
> phase throughout the transmission window.  Should such a situation occur,
> remember the first half of the X10 signal is not repeated.  That would be
> the same strength as that received from the XTB-IIR at that node, and the
> receiving module should have no trouble responding to that first half of
the
> command.

I didn't expect there to be any trouble.  I've been operating a number of
ControlLinc Maxi's, MiniTimers and TW523's through XTB's and then through
the XTB-IIR that's installed at the circuit breaker panel without any
noticeable problems.  The very faint X-10 signal noise I can hear if a chime
module's plugged in too close to the XTB isn't really a problem - it makes
me wonder if the human brain could distinguish the different commands if
they were a little louder.

Anyway, I'll take some more measurements when I get a chance.  The next
thing I want to see is whether the XTB-IIR can punch a signal through the
AF120 when it's not boosting an XTB signal.

--
Bobby G.