On 2019-12-17 01:39 PM, Lew Wolfgang wrote:

Moving this interesting thread to off-topic.

On 12/16/19 2:20 PM, James Knott wrote:

...

On 2019-12-16 05:17 PM, Patrick Shanahan wrote:

...

if a tree falls in the forest and no one hears it, did it make a sound?

The problem with that is interference with modern communications is not noticed until it causes a complete failure.  The signal is either receivable or or it's not, with little in between.  On FM radio, the signal to noise ratio would gradually decrease, but it took a fair bit to be noticeable.  It's not like AM radio where the interference was obvious.

So what are we to do?  Microwave ovens make interference, should we dump them?  Automobiles emit RFI from their ignition systems, and motors in household devices may generate voltage spikes due to inductive kick.  Ditch them all?

Microwave ovens, baby monitors, WiFi and other devices use the ISM bands, where there is no protection from interference.  Auto engines produce nowhere near the interference they used to.  One of the first steps to reduce it was the resistor spark plugs, which have an internal resistor.  Also, the frequencies generated by cars, motors, etc. are fairly low, so by the time you reach the VHF spectrum, they're gone.  This is not the case with data over power lines.  As I mentioned, they symbol rate for 100 Mb & Gb is 125 M symbols (baud) per second.  This means a much greater potential for interference with modern communications.

IEEE and others have standards for powerline systems that are approved by the FCC.  I don't hear any trees falling in my forest, should I ask my neighbors if they hear falling trees?  Presumably I'd be the first to be affected by EMI/RFI from my own devices, true?

BTW, last night I found my old AM/FM radio that I haven't used for more than ten-years, at least.  I set it to the AM band and walked around a bit listening to both the upper and lower bands between stations.  It actually works as a very crude interference collector!  I was able to hear interference from the powerline adapter itself at about 15-cm.  Farther away than that it was undetectable.  I followed the in-wall power wires and didn't pick up anything.  The Visio flat-screen television was much noisier than the powerline adapter, as was the microwave oven, even with it not cooking anything.  I should make a more detailed survey sometime. Granted, using an AM radio like this isn't a true field strength meter, but it's still a data point.  The neighbor's SSB interference would have boomed in, swamping even 50-Kw clear-channel AM stations.

Regards, Lew

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