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Re: Line Noise Interference Question



In article <42c9186b.166143714@xxxxxxxxxxxxx>, nobody@xxxxxxxxxxxx (Dave Houston) writes:

| AFAIK, all of the diagnostic tools available have similar frequency
| responses. If Dan Lanciani is right, its possible to have a noise source
| that will not show up on them that will still jam X-10. He said he had a
| ~200kHz noise source that interfered with X-10 but did not register on the
| ESM1. I'm not sure whether he was using the ESM1 that I loaned him
| (fullscale=10Vpp) or an ELK model (fullscale=5Vpp).

It was a brand new, out-of-the-box Elk model.  Note that the original Leviton
test unit did not register either.

| It might be that it
| would register on the latter but not the former. It's hard to say because he
| really didn't provide much detail about the actual frequency and amplitude.

The actual frequency was just over 200kHz, perhaps 205kHz.  That's as close
as I can estimate looking at a scope.  The amplitude was quite low (maybe
50mV--I don't remember), affecting only two-wire wall switches in their
off state.

To confirm the frequency response of the Elk meter at more reasonable amplitude
I used an old remote control box which conveniently generates a steady 197kHz
carrier at several volts.  Again the Elk read nothing but all X10 operation
on the line was inhibited.  (I.e., this is an even better jammer than the
200khz signal generator I had used before. :)

Finally, I reprogrammed an RR501 (using my own firmware) to use 192kHz
carrier for normal X10 transmission.  Its transmissions were accepted
by every normal X10 receiver I tried (including a CM11a).

As I've said, the cycle-counting technique used in many X10 receivers helps
only with noise of lower frequencies and the analog filters don't have that
sharp a cutoff.  Test tools are doing you no favor by implementing a band
filter narrower than that of the actual receivers.

Last time I posted about this you said you had ordered a signal generator so
you could test the frequency responses for yourself.  What did you find?

				Dan Lanciani
				ddl@danlan.*com


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