Joe Zeff:
Indeed. At one point, I was doing senior tech support for an
ISP. One day I got a call from a customer who was having connection
issues with his ADSL, and the description made it sound like line
noise. After asking some questions, I learned that the cable from
the phone socket to the modem was too long and he'd coiled it up. I
explained that this just made an electromagnet out of the line and it
was causing interference with itself. I told him to get a shorter
cable, and not let it get coiled again. AFAICT, problem solved.
If they used twisted pair in the phone cables inside your house, and
the phones and modem equipment you plug into it, instead of just
parallel wires, it'd eliminate a lot of interference problems. I got
rid of an awful hum and buzz, in mine, by doing that.
And I used to have a portable USB hard drive that would kill off my
ADSL. It had an el-cheapo switchmode power supply that radiated so
much crap that it didn't matter where it was plugged in (inside any
room in the house), it'd instantly kill the ADSL, and it'd never
recover until the hard drive was unplugged.
It didn't have to be connected to anything related to the modem to
wreak it's havoc. I could plug in an isolated computer (just the mains
plug into the wall socket), and connect the hard drive to that
computer, and that would do the damage. Didn't even have to turn the
computer on.
You can get similarly annoying mains hash from household lighting
dimmers. And just about every appliance has a switch mode power
supply, these days.
--
[tim@localhost ~]$ uname -rsvp
Linux 4.12.14-300.fc26.x86_64 #1 SMP Wed Sep 20 16:28:07 UTC 2017 x86_64
Boilerplate: All mail to my mailbox is automatically deleted.
There is no point trying to privately email me, I only get to see
the messages posted to the mailing list.
It seems the modern trend with Linux programmers is to change existing software
so that it's more annoying to use (e.g. making reboots required, when they
never used to be), then denying that *that* is a nuisance, then saying it's
necessary (ignoring that several years of prior versions didn't have that
stupid requirement), then complaining about being criticised for making things
worse. Don't try giving me an Emperor's New Clothes routine, it won't wash.