Re: Line Noise Interference Question

[nobody@xxxxxxxxxxxx (Dave Houston)]

"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.