All of this makes sense, but the modem may also contributing through
poor circuit board layout. That's an important part of the difference
between models of modems. And, of course, shielding.
In the olden days, all telco wiring WAS twisted pair, but far too much
parallel conductor cable has come into the system. CAT5 and other cable
for wired Ethernet is VERY VERY good at minimizing leakage of the
differential signal from wiring, and pickup on that wiring to the
differential pair. That's because it is VERY high quality twisted pairs,
with many more turns per inch than traditional land line twisted pair.
So -- one of my primary recommendations for RFI to/from anything telco,
including DSL, is to have telco provide CAT5 or better for the last
1,000 ft or so of the run, and for a greater distance if possible. Note
that you may also be hearing your neighbors modems and leakage from
their wiring. My second primary recommendation is to apply very good
common mode chokes to every cable connected to the modem and to the
telco wiring itself.
Most of this and a lot more is documented in
http://k9yc.com/KillingReceiveNoise.pdf
Two other points -- you've already done the right thing by complaining
to AT&T, but don't stop there. Contact ARRL's RFI group and get their
help in dealing with AT&T. And as others have noted, keep careful notes
of all of your contacts with AT&T.
73, Jim K9YC
On Fri,3/17/2017 12:37 PM, John Saxon via Elecraft wrote:
If I am reading it correctly, they are saying that the bands that Uverse uses for
multiplexing includes 160,80 & 40 frequencies. One of the contributors said that
AT&T eventually upgraded his equipment, including replacing some twisted-pair
cables with CAT5 cables, and it solved the problem.
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