Howdy all. I recently upgraded my internet connection from dial-up to
high speed via cable (about time, I know). Since installing the cable
I have been having problems getting connected to the internet. If I
connected the modem straight to the cable drop coming in the house I
would get a good connection, but when I run a cable from the drop to
the computer (about 25', no splitters) I would fail to get a
connection. Sometimes it would connect, but most the time it would
not. So, I got to looking at the cable run (finished basement, drop
ceiling) and discovered that in two places the cable was running along
side and sitting right on top of some romex. Hmmm, I thought to
myself. Could I be getting interference on the cable from the romex?
So, I moved the cable several inches away from the romex and low and
behold a got a good internet connection.
I have a cable guy coming out later this week to check my signals so
I'll ask him if the electric lines could cause enough interference to
affect my internet signal. It appears so and makes sense to me
especially if the cable is right on top of and running parallel with
the romex. Has anyone had any similar experiences?
There is coax and there is coax. Some
coax is not meant for the broadband
signal from cable TV. Some Coax has
very poor shielding. Some older coax
for VHF/UHF TV was not 100% shielded.
Check the type
of cable in your run as that might be
part of the problem.
On Feb 19, 9:32 pm, firstname.lastname@example.org wrote:
Apparently nobody read my full post. I have no problems with the
cable. I did have until I move my cable line away from the electrical
lines. I was just curious if anyone has had a similar experience when
running a cable internet line too close to an electrical line.
Because I was getting suggestions on how to fix the problem. I said in
my post that the problem appears to be fixed. I was only hitting on
anyone with similar experiences.
Okay, I see what you mean. I am using thr cable supplied to me by the
cable company (Time Warner - Road Runner). It is RG-6. Still no
problems since I moved the cable away from the electrical lines. So,
to me that implies I was getting interference from the electrical
lines. Maybe, maybe not. It's only been 24 hrs since I "fixed" the
problem. I'll ask the cable guy when he comes out.
Sorry for any misunderstandings.
I think you have another problem. The cable runs for miles on a pole
in line with 13kv or more on the top strand and usually a 120/240v
secondary. The ingress into the coax is negligable and intentionally
blocked anyway. My cable splitter/amp is about 2" from my electrical
panel with no problems.
If I had to bet on what you have going on I would say it was a bad
termination on your cable. The cable guy will usually cut off all the
ends and put new snap/lock ends on ... just to protect his plant. In
the end, the cable company is responsible for preventing ingress. That
is why they cringe when homeowners start stringing cable.
no. but clarification needed: this sounds like a self-installation
that simply needs a cable company technician. our cablemodem runs off
basic time warner RG6 cable wire. the cable company in buffalo ny
installs and maintains it. does yours?
are you speaking of a second type of wire, ethernet [category___]
wire fed from a router? here that is maintained by the homeowner.
I have cable internet, which works well. I put the modem as close as I
could to where the cable enters the house, and ran ethernet (CAT5)
cable the rest or the way. Also, CAT5 is easier to handle than coax.
And (once you get a good connection) there's other things to worry
about. An inexpensive router between the cable modem and the
computer(s) is a good idea, even if all you have is one computer.
You can ask the cable company about that (SOME are helpful that way),
but there's really no need to. It's YOUR network.
This is my second try, but my response from yesterday
didn't show up in my list today.
You did the right thing in moving the coax away from the
Generally speaking, it is a bad idea to run
communications cables parallel to power cables. There
is always a good chance of interference. When I was an
engineer at NASA the standard policy was to never run
power cables and signal cables in the same raceway. And
when signal and power cables have to cross they should
cross at right angles.
Even if there is no apparent problem when running power
and signal cables together there may be when unusual
power conditions occur. I have been told of severe
consequences when such events occur.
In the home power and signal cables should always be run
in separate wall cavities.
That is certainly a good theroretical design goal but reality is the
power company and the telco/cableco share the same poles and
underground ducts so their wires do run parallel for hundreds of
If you are getting ingress on coax or twisted pair, you have another
problem. I bet you could see it using TDR in a second.
On poles, they are often a few feet a part. What is the range or field that
is going to matter? I would imagine the difference between a couple of feet
and touching makes a difference in signal, magnetic field or whatever.
It will still add up and on a power pole in a neighborhood you usually
have a single 13kv unbalanced primary. In your house they use balanced
cables with a hot and neutral or 2 balanced hots.
When I was doing communication wiring we set up a torture chamber in
the office and did everything you "can't" do like looping LAN cables
around florecent fixtures and running along next to the building
feeders from the transformer. We found that if everything was
terminated properly it had zero effect. It was only when we had other
problems that it screwed up the data.
This was using test programs that collected LAN statistics with
unusually high loading.
Again, the TDR flagged these problems immediately. Coax and twisted
pair are very good at eliminating outside interferance
That means that good design rules don't apply because
you know that they don't really mean anything. And of
course everybody lives in an ideal world where all
circuits are properly terminated and there is never any
need to follow the design rules.
Power and communications lines do not share conduit in
long distance runs. They may be "near" each other, but
they are separated not only by space but by earth which
makes a pretty good shield.
On the pole out in back of my house the telephone and
cable lines are something like 6 to 10 feet from the 220
lines and about another 20 feet from the 7 KV lines.
With the square cube drop in level that makes quite a
difference in the interference level between say 6
inches and 10 feet.
And power lines are not balanced. One side is grounded,
both the neutral and the ground are grounded at the
entry point to the house. The closest you can come
to a balanced power line is a 220 line. And that
may not be completely balanced, because the device
connected to it may have a 120 circuit in it that will
cause an unbalanced flow in the 2 legs.
The best thing to do, even under ideal conditions is to
always follow conservative design rules. That will help
to take care of the cases where things don't meet the
ideal that you say will take care of all of our problems.
If you don't make good terminations all the routing design rules in
the world won't help that much and if the terminations are good it
doesn't matter. Coax and twisted pair are very robust transmission
methods. Certainly you can go around separatring cables and
rearranging them so they cross at perfect 90 degree angles but if that
is fixing anything you are just pissing on the fire. That time would
be better spent fixing the NeXT problems you have from bad
terminations and impedance problems damaged cables.
I never designed anything but I fixed them for 40 years. I know what
I've said it before. Good design rules are good at any
time. Good design rules do include good terminations,
but they aren't everything. Follow good conservative
design rules and the chance of ever having a problem is
much reduced. Don't throw out the baby with the
bathwater just because you have all the answers. Not
too long ago I had a cable tech in because I was having
an intermittent cold weather outage. He walked in and
jumped right on the connectors on my cables and refused
to listen when I tried to tell him the problem. The
system was working when he got there, because he got
there after sun rise and it had, as usual, started
working. I admit he got a little better signal on my
TV, but he didn't fix the problem and refused to admit
that there was a real problem. It sounds a lot like you.
There are other problems than just bad connectors. And
the way to help reduce them is to follow good design
rules in all cases.
This is highly correct.....running parallel to electric ( AC ) lines
will cause interference. AC lines create a magnetic field around the
AC wire.......when running Cable line parallel to it; the magnetic
field basically raps or surrounds the Cable line and therefore causing
interference. Note-The magnetic field will not be felt if cable line
is run at a 90 degree angle across the AC line nor if cable line is
far enough away from the AC so that the "M" field does not encircle
it. But- you got it and found it.....good job!!
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