Magnetic Fields, Phone Lines, and Data Disruption.

General Questions
#1

Came across some rather powerful magnets at work which led to some experimentation of various sorts. Ended up bringing one of them home. Computer is hooked up to a standard twisted pair which supplies an extremely slow connection. Tests were performed with the computer idling, as well as during uploads and downloads.

With the magnet sitting on the phone line, and a timer and transfer rate program running, no differences could be detected with or without the magnet. There did not appear to be any problems with the information and images up or downloaded.

By varying the distance of the magnet from the wires and moving it extremely rapidly in a circular manner, incoming and outgoing data could be thoroughly scrambled or only slightly disrupted. Once, and then unrepeatable thereafter, the connection was lost. No way to know whether the magnet was the cause or not.

Even with a moderately passable understanding of electricity and magnetic fields, I was actually surprised at these results. I’ll be in search of a gauss meter that can be borrowed, to quantify and compare the strength of the magnetic field being used. This was an amazing magnet being played with, but still the results were unexpected.

Are there any thoughts out there that might help those of us with less than adequate training to more completely understand what happened here? My guess would be that any offerings need not go back as far as magnetic fields, wire, and induced flow. Personally, my hang-up seems to be with a permanent magnet that can be carried by one person accomplishing what was experienced.

#2

A moving magnetic field induces an electric charge, whose strength depends on the rate of change of the field (so if you stop moving it, the field goes away). If this electric field impinges conductive wires (such as your telephone wires), electric current results. This current must have interfered with the analog modem signals.

If the wires were perfectly twisted (i.e. infinite twists per inch), the fields hitting each wire would have canceled out. Your wires may only have had 1 twist per inch or so, which must not have been enough to cancel out your rapidly moving field.

Arjuna34

#3

Thanks Arjuna34.

It would seem almost certain that the modem was interfered with, particularly when one takes into account that the moving field does nothing to the quality of conversation on a standard telephone. What is confusion is that when using the full duplexing capabilities of the modem along with a microphone and headphones, the moving magnet had no effect whatsoever on an ongoing ‘through the computer’ phone conversation. I had fully expected some degree of interference based on the first experiment. Now I am even more confused.

Any thoughts from anyone would be appreciated.