Re: Line Noise Interference Question

["Robert Green" <ROBERT_GREEN1963@xxxxxxxxx>]

"Dave Houston" <nobody@xxxxxxxxxxxx> wrote in message
news:42c80d52.98013938@xxxxxxxxxxxxxxxx
> "Robert Green" <ROBERT_GREEN1963@xxxxxxxxx> wrote:
>
> >"Dave Houston" <nobody@xxxxxxxxxxxx> wrote in message
> >
> >> With a 5V signal level even the 30:1 filter will allow 167mV through
and
> >> many transmitters have a 10Vpp signal level.
> >
> >I noticed that when I put an ACT 5A filter between a signal sucker and
the
> >line that a maxicontroller could still reach and control an appliance
module
> >located very closer to the other side of the filter.  I also noticed very
> >odd results combining a surge protector with a Leviton filter.
> >
> >I confess to not having read up as much as I would like on filter design,
> >but perhaps you can give me some guidance.  Is it possible for two
"signal
> >suckers" to interact in unexpected ways?  I plugged two surge strips that
> >gave me X-10 troubles and used the ESM-1 to measure a signal at the end
of
> >both of the units.  It was higher at the end then it was in the middle.
Is
> >that even possible?
> >
> >[outlet] (2v)---------->[strip1] (.5v)---------->[strip2](1.5v)
>
> It may be that the combination is creating a resonant circuit. That's why
I
> suggested to the OP that he remove the powerstrip and test with just the
> filter. It's always best to start with the simplest possible setup.
>
> Without knowing exactly what components are used in each filter, it's hard
> to say what interactions are possible.
>
> Ground loops might cause erroneous results.
>
> >Since I can't get the level of precision I want from the ESM-1, I decided
to
> >bite the bullet and buy the Monterey unit.  The Lynx wasn't very useful
to
> >me in making detailed analyses of the "power picture" at my house. The
ACT
> >unit was just too damn big.   From what I read, aside from the BSC
problem,
> >it's going to give me a signal and noise readout that promises to be
useful
> >in both bug hunting and testing.
>
> I didn't think the Lynx-10 PLC would be very useful as a test instrument.
I
> also hate to see anyone spend so much money for the Monterey. The Monterey
> maxes out at 4.096V so, while being able to measure =<200mV is probably of
> most importance, you will not be able to profile your transmitters since
all
> will output more than the Monterey can measure.
>
> If you open up your ESM1, you'll find a potentionmeter that sets the
> fullscale reading. I would mark at least two settings on it - one that
sets
> fullscale with one of the 10Vpp transmitters and one that sets fullscale
> with a 5Vpp transmitter. The latter will give the most sensitivity at low
> signal levels.
>
> As I understand it, ELK adjusts the fullscale reading to agree with a
> Monterey which means it maxes out at 4.096V as it comes from the factory.
>
> >What I want to do is design a test bench that can not only get some sort
of
> >"device profile" for all my 110VAC equipment.  I was going to set up the
> >meters (I want to make sure the ESM-1 and the Monterey agree) on a plain
> >vanilla power strip plugged into an ACT 15A filter.  Is that a good idea?
> >I'm worried that devices might react differently in the test bench than
they
> >might in the real world.  What else should I be measuring to try to
> >eliminate variables?  I want to know which devices present obstacles to
X-10
> >signal propagation but I don't want to waste time recording worthless
> >readings because I didn't think it through first.
>
> I've found that plugging everything into one powerstrip makes for
resonably
> reliable benchmarks. That's how I measured the outputs of the various
> transmitters at http://www.mbx-usa.com/x10-sig.htm. You need to be careful
> about having other transmitters between the test transmitter and whatever
> you use for a meter since transmitters will attenuate the signal.
>
> The filter will provide further isolation but you probably don't need it
> unless there are signal suckers nearby. You can verify this by taking
> readings with and without the filter in place.
>
> It really is a shame that the web site that had all those papers on
> powerline communications was taken down. There were some really
informative
> studies there that, if nothing else, illuminated the complexity of using
the
> powerline as a communications medium. The powerline acts like a
transmission
> line with a characteristic impedance that varies from ~2-80 ohms. Like any
> transmission line, there can be reflections, nulls and peaks.

I decided I wasn't as concerned about the Monterey's lack of max voltage
indication as I was that the ESM-1 and the Monterey agreed.  In fact, it was
you message about how the ESM-1 was calibrated at the factory to agree with
the Monterey that made finally decide to buy one.  That turns out to be a
plus for me since one meter can serve as a sanity check for the other in the
face of bizarre readings.  As far as profiling the transmitters that
overwhelm the Monterey, I can read them through a filter I'll keep offline
as a "reference attenuator" that shifts the signal into the range the
Monterey and ESM-1 are set to measure.  Not ideal, and certainly not useful
to compare my readings to anyone else's, but it shouldn't affect my goal of
having baseline numbers for every device.  I wonder if the Monterey has a
similar potentiometer to the ESM-1 for adjusting the scale?

This has got to be the most heavily researched thing I ever bought!  )-:
I've read lots of previous threads about the unit, particularly between you
and John Gavin (sp?) where you discussed decay rates of the CM11A signal and
methods of measuring the signal quality (where on the AC cycle samples are
taken, how many, etc.).  I struggled mightily with the Monterey over the ACT
that Bruce R. likes and decided as long as neither has an output port, the
smaller size of the Monterey makes it worth the premium.

While an oscilloscope would be the best way to look at an X-10 signal, on a
practical level, I need something I can tote to the places I have having
problems.  I forsee getting the USB scope you cited a while back, but right
now I need real world tools that help me diagnose the few intermittent
problems that still plague me.

As for a test bench, it's going to be hard to keep it isolated from other
X-10 transmitters, which I learned through you and Google all attenuate (is
that the right word in this context?) the X-10 signal slightly.  I've got
*lots* maxis and minis deployed house-wide.

I thought about plugging the test strips into two 100' 14AWG extension cords
I have just to put some distance between the test bench and the rest of the
house, but your suggestion of measuring with and without a filter will
probably tell me (with the Monterey or a scope, at least) whether there's a
signal sucker on that circuit leg.  If the measurements are too far out of
synch, I might go back to the 200' of cord idea.

Probably the best way to test would be to shut down all breakers in the
house except for the one I was using to test, but the last time I did that,
I got into BIG trouble for blowing up the VCR's programming.  (Actually, I
did it twice.  When I reset the programming, I inadvertently set the time
for AM instead of PM.  Oddly enough, the unit seemed to be coming on at the
right times, but in reality, they were out of phase by 12 hours).

Since the great breaker box fiasco, SWMBO has put a limit on the number and
type of "research projects" I can engage in at any one time.  I have to
apply for permission to shut off the panel since I mucked up the recording
of a "Series Finale."  The currently approved project is to get the HAI Omni
LT function as a basic alarm system, capable of calling a series of numbers
when an alarm event occurs.  I have one week, starting tomorrow, to get it
done!  (So, why am I here in CHA, you ask?)

Wasn't someone in CHA measuring their home's impedance at the breaker box?

I saw an article that talked a bit about powerline impedance here:

Protocol to Avoid Noise in Power Line Networks
engrwww.usask.ca/research/ ee/faculty/ded632/files/Powerline2005.pdf

And there's an enormous powerline FAQ at:

http://links.epanorama.net/links/wire_mains.html

That's looks to be chock full of interesting wiring information, but it will
take me a month to get through.  I wouldn't be surprised if it pointed to
some of the links that were lost when that powerline website went missing.

Thanks again for you insight, Dave.  I'll be sure to post when "Monty"
arrives.  My main purpose in buying it is to get very accurate readings of
the X-10 signal strength at multiple points throughout the house.  There are
just too many "semi signal suckers" that seem to cause a degradation of the
signal, but it's just too small a voltage for the ESM-1 to see it (and I've
tried videotaping the display and playing it back in slow motion to see if I
could see a difference in the # of bars lit per frame).  That's when I
decided that despite its shortcomings, the Monterey is going to give me the
degree of precision I need as admirably as it's going to unfill my wallet.
:-(  It really is just a little too expensive to make me feel really
comfortable with it, but my vendor assures me they'll take it back if I
don't like it.  We'll soon see!

--
Bobby G.