I'm going on a service call next week to address an issue of AM radio
interference on a telephone line. The lady has her computer connected
to this line and it seems to keep getting bumped off especially
throughout the day. There is a 5KW AM transmitter operating on 610KHZ
about a quarter of a mile from the customers home. At night they drop
their power to 1.0KW and she tells me the interference decreases. She
has tried filters purchased from Radio Shlock which were marked ".50MHZ
to 3.0MHZ but apparently they did not help.
The other day while discussing this with her on the phone, (she called
me from her work so I have never heard the interference), she told me
that someone had suggested that she plug her modem dierectly into the
interface on the side of the house. The length of cord used was
approximately 15 feet. When she did this she found that there was
apparently no interference problem. I'm suspecting then that if the
line is clean up to the interface, then the telephone company has
perhaps already addressed the close proximity transmitter issue in her
neighborhood using sheilded wire and perhaps filters on the street and
that her problem is the straight untwisted wiring throughout her home
which may be acting as an antenna.
I've considered running a new sheilded wire from the interface,
grounded to the telephone company's ground, directly to her computer.
I would try that first with no other house wiring connected.
In theory if that were the only line connected then that should work.
However, I would suspect that as soon as I would connect her existing
house wiring back up to the interface, (essentially reconnecting the
"antenna") the problem I would suspect would return.
Should I plan on completely rewiring the house with sheilded or does
anyone have any another ideas they might suggest? Thanks very much for
any assistance. Lenny Stein, Barlen Electronics.