Streetlight and Appliances problem

Does the noise come from the speakers, or from inside the box with the volume turned all the way down also?

You might try a noise reducing surge protector power strip (glorified extension cord) to plug the computer and television into.

You might try improving the grounding. Get a long (bare or insulated, #14 to #18 gauge) wire and daisy chain it from one piece of equipment to the next. For the computer, attach it to one of the screws that holds the back cover in place. For the television, attach it to one of the stud jacks in back for left/right audio or composite video (yellow). Connect the far end of the wire to a known ground. For the latter you might get away with a radiator or a water pipe or the screw that holds a receptacle cover plate on but a sure shot is down the basement stairs to the electrical panel or the fat bare ground wire coming out of that.

Note that plug in noise reducers (that "clean up" "dirty" power) draw some power 24/7 unless unplugged. The harmonics that get filtered out are dissipated in a manner not too different from running a light bulb or heater and that counts as billable power.

nagareru said:

Hello, I think too it is a problem with harmonics. I have been looking for an on-line UPS, the problem is that on-line ups are just too noisy 45db and up. That is just too much. Besides that I cannot find a device that can filter the harmonics. I called the power company already, they sent a guy who said never heard of something like this (which I believe) because he said he couldn't listen to anything! The sound is kind of high pitched and I can hear it very well at use-distance from the computer.

How about a surge protector with some noise filtering? Would that help?
When I google "Harmonic Filter" in google, only industrial ones appear... am I doomed? T-T

Click to expand...

I don't know of any surge protector that will filter harmonics. You get minimal filtering with caps.....it really takes an inductor coil to filter out the high freq stuff.

As for UPS's....unless you spend $500 or more, the lower end models (which are still good devices) do not filter out line noise in normal mode. In other words, if your power is not in a brown out condition or off, then the AC power bypasses the inverter in the UPS. It's only when you go on battery power that things get cleaned up.

With that said....it's worth having a UPS on your computer. The surge protection in them are typically much better than your Wallmart surge outlet strip.

This is what I use at home.....



The one I have is good for about 15 min computer time....I think I paid $75 for it....if I kill the computer....I can power a CFL light for more than an hour.....if you don't mind the beeping....

Not exactly on topic but power line interference can be difficult to remove particularly on circuits providing large current draws. A "choke coil" can be put in line (in series) with the load to filter out most of the higher frequency noise. Also capacitors are placed across hot and neutral and/or in parallel with the coil. With both capacitor(s) and coil(s), we have a "tuned circuit" that passes the 60 Hz power with little loss but more loss compared with a straight wire and enhanced although still not perfect blocking of other frequencies.

The college I attended had a central clock synchronizing system (by Simplex) that injected a high frequency tone into the power lines. (It was for a few seconds every hour.) The college had its own substation and the tone was injected there. The tone was heard in most audio equipment and even from some light bulb filaments and some electrical equipment in every campus building and also in a few homes and town buildings near the substation. Several unsuccessful attempts were made over the years to eliminate the tone from the campus radio station broadcasts.

Incidentally, in earlier years the college radio station broadcast its signal via power lines rather than over the air. A radio placed near a power line, including wires in the wall daisy chaining from one receptacle to the next, would pick up the signal.

I do not think that the spurious frequencies would cause damage to computers and modern electronics. The power is rectified (converted to direct current) before being used by the circuits, and the filtering contained in the power supply removes a much greater percentage of higher frequency ripples when performing the needed function of smoothing out the 60 and 120 Hz ripples coming from the rectifiers proper.