| Author |
Message |
Michael A. Terrell
Guest
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 Posted:
Fri Sep 16, 2005 8:35 am Post subject:
Re: due to some kind of interference, monitor display is "sh |
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"John H." wrote:
| Quote: |
hi, I have two monitors connected to my ati card.
I have
coax on wall - > cable modem surge protector (very small
-> 2- way splitter -> cable modem
-> tv card on pc
there is a line off the surge protector which goes into screw
in order to ground it.
OK, so there are several weird situations from this. If I have
coax from splitter to TV card, and I do not ground it to wall
outlet, both monitor displays shake REALLY heavily. If I ground
it to wall outlet, large 19 inch CRT shakes some, but not nearly
as much(where I am at now).
Now, if I move computer and two monitors to other side of room
with no peripherals attached, no shaking. If I simply plug the
surge protector into the coax on this side of the room, and ground
is connected, even though NOTHING Is connected to surge protector,
on the clear other side of the room, both monitors begin shaking!
I need a way for everything to live in harmony:( The shaking,
even though it is minor right now, is mild, but still too much:(
I know a lot about computers, but not too much about electronics.
How can I get rid of ALL shaking?
thanks!
|
How close are the monitors to each other? You can have interaction
between the electromagnetic deflection, and other wires in the area can
change the field strengths. If you are running the same scan rates you
can have this problem. If you can change one monitor to another rate
and it goes away you need to put something between the monitors to block
the magnetic fields. A simple sheet of steel spaced fairly evenly
between the monitors can do the trick.
--
?
Michael A. Terrell
Central Florida
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Tomi Holger Engdahl
Guest
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| Posted:
Fri Sep 16, 2005 3:36 pm Post subject:
Re: due to some kind of interference, monitor display is "sh |
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w_tom <w_tom1@hotmail.com> writes:
| Quote: | The only device that would be effective on the cable was
something that galvanically separates the cable from the
household appliances. IOW something containing a transformer
- not a filter.
|
You are right the device that is needed is something that
galvanically separates the cable from the household appliances.
Well made galvanic isolation can be made with suitable transformer
(need to be carefully deisgned to well cover the whole
frequency range used in TV cable without too much attenuation
and impedance mismatch).
Other technique used for isolation is to use isolator based
on two capacitors. It is kind of speacial hign pass filter
on both of the signal wire and the shield. This filter does not
pass through any considerable mount of 50 Hz / 60 Hz mains current,
but still passes the antenna signals (50-1000 Mhz) nicely.
Both antenna signal isolator types are described in my document at
http://www.epanorama.net/documents/groundloop/antenna_isolator_building.html
| Quote: | Meanwhile, did you verify the earthing of cable, AC
electric, etc to a common earth ground at the service
entrance? That is even required by code AND often violated by
cable companies who hire on price rather than on technical
knowledge.
|
It is a good idea to check this.
--
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at
http://www.epanorama.net/ |
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Jasen Betts
Guest
|
| Posted:
Fri Sep 16, 2005 4:35 pm Post subject:
Re: due to some kind of interference, monitor display is "sh |
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subj:
it could be magnetic: You don't by any chance have a desk fan or another
monitor next to the monitor do you :)
--
Bye.
Jasen
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Jasen Betts
Guest
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| Posted:
Sat Sep 17, 2005 12:35 am Post subject:
Re: due to some kind of interference, monitor display is "sh |
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On 2005-09-14, John H. <mistamaila@nospam.gmail.com> wrote:
| Quote: | ok, the thing i bought from radioshack is
75-ohm tv/vcr/fm interference filter
????
|
I think those are to block HF CB-radio signals, it's unlikely that such a
device will help.
those URLs look promising.
--
Bye.
Jasen |
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Jasen Betts
Guest
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| Posted:
Sat Sep 17, 2005 12:35 am Post subject:
Re: due to some kind of interference, monitor display is "sh |
|
|
On 2005-09-13, John H. <mistamaila@nospam.gmail.com> wrote:
| Quote: | I found something at radio shack that says it's an antenna
something, and it's coax to coax, but says it is more for
tv, and it's $5.99. It's 75ohm. would that do the same thing as
what you suggested?
|
if it's an atenuator or an ampplifier or a DC blocking module it's not
suitable.
A dc blocking module goes half way to the solution by stopping current in
low frequency current in the centre conductor. you'd have to modify it by
cutting the outer concurtor and installing some ceramic capacitors across
the gap. if the unit has a metal case that's not easily opened it'd probably
be easier to build an isolator from parts.
Bye.
Jasen |
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Jasen Betts
Guest
|
| Posted:
Sat Sep 17, 2005 12:35 am Post subject:
Re: due to some kind of interference, monitor display is "sh |
|
|
On 2005-09-09, John H. <mistamaila@nospam.gmail.com> wrote:
| Quote: | hi, I have two monitors connected to my ati card.
I have
coax on wall - > cable modem surge protector (very small
-> 2- way splitter -> cable modem
-> tv card on pc
there is a line off the surge protector which goes into screw
in order to ground it.
OK, so there are several weird situations from this. If I have
coax from splitter to TV card, and I do not ground it to wall
outlet, both monitor displays shake REALLY heavily. If I ground
it to wall outlet, large 19 inch CRT shakes some, but not nearly
as much(where I am at now).
Now, if I move computer and two monitors to other side of room
with no peripherals attached, no shaking. If I simply plug the
surge protector into the coax on this side of the room, and ground
is connected, even though NOTHING Is connected to surge protector,
on the clear other side of the room, both monitors begin shaking!
|
I think the surge protector is causing a ground loop in your coaxial
and/or mains cable.
to reduce this effect possible move it closer to the service
entrance for the electricity and cable. that way the loop will
exist mostly outside your dwelling and thefore the electromagnetic
effects of it will bereduced.
--
Bye.
Jasen |
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John H.
Guest
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| Posted:
Sun Sep 18, 2005 12:35 am Post subject:
Re: due to some kind of interference, monitor display is "sh |
|
|
On Fri, 16 Sep 2005 04:42:33 +0000, Michael A. Terrell wrote:
| Quote: | "John H." wrote:
hi, I have two monitors connected to my ati card.
I have
coax on wall - > cable modem surge protector (very small
-> 2- way splitter -> cable modem
-> tv card on pc
there is a line off the surge protector which goes into screw
in order to ground it.
OK, so there are several weird situations from this. If I have
coax from splitter to TV card, and I do not ground it to wall
outlet, both monitor displays shake REALLY heavily. If I ground
it to wall outlet, large 19 inch CRT shakes some, but not nearly
as much(where I am at now).
Now, if I move computer and two monitors to other side of room
with no peripherals attached, no shaking. If I simply plug the
surge protector into the coax on this side of the room, and ground
is connected, even though NOTHING Is connected to surge protector,
on the clear other side of the room, both monitors begin shaking!
I need a way for everything to live in harmony:( The shaking,
even though it is minor right now, is mild, but still too much:(
I know a lot about computers, but not too much about electronics.
How can I get rid of ALL shaking?
thanks!
How close are the monitors to each other? You can have interaction
between the electromagnetic deflection, and other wires in the area can
change the field strengths. If you are running the same scan rates you
can have this problem. If you can change one monitor to another rate
and it goes away you need to put something between the monitors to block
the magnetic fields. A simple sheet of steel spaced fairly evenly
between the monitors can do the trick.
|
they are about 1 foot from each other, however, that's about how
close they were at the other location.
the first is a 19 inch crt, at 1600x1200, the second is a 15
inch fp, at 1024x768.
So I am not sure it's the two monitors causing the problems
together? |
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John H.
Guest
|
| Posted:
Sun Sep 18, 2005 12:35 am Post subject:
Re: due to some kind of interference, monitor display is "sh |
|
|
On Sat, 17 Sep 2005 09:03:19 +1200, Jasen Betts wrote:
| Quote: | On 2005-09-09, John H. <mistamaila@nospam.gmail.com> wrote:
hi, I have two monitors connected to my ati card.
I have
coax on wall - > cable modem surge protector (very small
-> 2- way splitter -> cable modem
-> tv card on pc
there is a line off the surge protector which goes into screw
in order to ground it.
OK, so there are several weird situations from this. If I have
coax from splitter to TV card, and I do not ground it to wall
outlet, both monitor displays shake REALLY heavily. If I ground
it to wall outlet, large 19 inch CRT shakes some, but not nearly
as much(where I am at now).
Now, if I move computer and two monitors to other side of room
with no peripherals attached, no shaking. If I simply plug the
surge protector into the coax on this side of the room, and ground
is connected, even though NOTHING Is connected to surge protector,
on the clear other side of the room, both monitors begin shaking!
I think the surge protector is causing a ground loop in your coaxial
and/or mains cable.
to reduce this effect possible move it closer to the service
entrance for the electricity and cable. that way the loop will
exist mostly outside your dwelling and thefore the electromagnetic
effects of it will bereduced.
|
how do you mean "Service entrance".
It's a small apartment, but the other one I was at was smaller
and i got rid of the "shaking" there.
I did, however, order a new UPS, so I don't know if that will help.
If I remove the coax surge protector, it seems to sometimes
be worse. |
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John H.
Guest
|
| Posted:
Sun Sep 18, 2005 12:35 am Post subject:
Re: due to some kind of interference, monitor display is "sh |
|
|
On Sat, 17 Sep 2005 09:35:57 +1200, Jasen Betts wrote:
| Quote: | On 2005-09-13, John H. <mistamaila@nospam.gmail.com> wrote:
I found something at radio shack that says it's an antenna
something, and it's coax to coax, but says it is more for
tv, and it's $5.99. It's 75ohm. would that do the same thing as
what you suggested?
if it's an atenuator or an ampplifier or a DC blocking module it's not
suitable.
A dc blocking module goes half way to the solution by stopping current in
low frequency current in the centre conductor. you'd have to modify it by
cutting the outer concurtor and installing some ceramic capacitors across
the gap. if the unit has a metal case that's not easily opened it'd probably
be easier to build an isolator from parts.
Bye.
Jasen
|
well, i have noticed sometimes now, not even having coax
connection, still problems with monitor shaking ... other times
it goes away after removing coax connection, so I am not even
sure that's what the problem is now??? |
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John H.
Guest
|
| Posted:
Sun Sep 18, 2005 12:35 am Post subject:
Re: due to some kind of interference, monitor display is "sh |
|
|
On Sat, 17 Sep 2005 00:55:37 +1200, Jasen Betts wrote:
| Quote: | subj:
it could be magnetic: You don't by any chance have a desk fan or another
monitor next to the monitor do you :)
|
I have two monitors near each other, as my video card supports 2.
If this is the problem, though, shouldn't it go away on one if
I turn off the power of the other? |
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John H.
Guest
|
| Posted:
Sun Sep 18, 2005 12:35 am Post subject:
Re: due to some kind of interference, monitor display is "sh |
|
|
On Thu, 15 Sep 2005 20:20:51 -0400, w_tom wrote:
| Quote: | The only device that would be effective on the cable was
something that galvanically separates the cable from the
household appliances. IOW something containing a transformer
- not a filter.
Are you ready yet to deal with magnetic fields generated by
underfloor and wall interior electric wires? Minor change was
observed when connecting and disconnecting things. That
reported nothing useful. A moved monitor created
improvement. Why? Classic reasons for a shaking monitor are
external magnetic fields or an unstable (and failing) power
supply inside that monitor.
Meanwhile, did you verify the earthing of cable, AC
electric, etc to a common earth ground at the service
entrance? That is even required by code AND often violated by
cable companies who hire on price rather than on technical
knowledge.
"John H." wrote:
yeah, it didn't fix it. does that mean the other suggestion
for device wouldn't either?
On Tue, 13 Sep 2005 23:11:48 -0500, John H. wrote:
ok, the thing i bought from radioshack is
75-ohm tv/vcr/fm interference filter
????
|
Well, I am not sure how much I can verify as it's an apartment,
and I cannot rip up things to check on things:)
As far as moving things, when I did move both monitors and
computer to other side of the room, yes the shaking seemed
to mostly go away, unless I plugged coax surge protector into
coax on wall and had grounder cable connected, even though
nothing was connected to surge protector!
however, it seems like sometimes the monitor shakes more than others,
any ideas? |
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w_tom
Guest
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| Posted:
Sun Sep 18, 2005 6:46 am Post subject:
Re: due to some kind of interference, monitor display is "sh |
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|
First ignore everything about the surge protector. It does
not even claim to protect your computer from transients that
typically damage electronics AND only complicates your
analysis. Eliminate it completely while trying to solve the
shaking problem. Nothing inside the surge protector will help
you solve this problem nor provide useful information.
Second, having all incoming utilities earthed at a common
point at the service entrance ... where utility wires meet
building wires ... will further eliminate possible reasons for
failure. This too is a question to grasp and answer almost as
if life depended on it. Unlike things like the surge
protector, the common grounding is not a 'witchcraft'
suggestion.
Not only turn off that adjacent monitor. Completely
disconnect it. As a potential source of external magnetic
fields, the only reliable test is to completely disconnect
that second monitor so that it never again need be a variable
in the analysis. Notice we want only definitive 'yes' or 'no'
answers.
Where in the apartment does shaking significantly increase
and decrease? You also know where the main breaker box is
located. From that, approximate where wires go from AC
electric box to the various apartments. Utility wire enters
the building where all apartment wires go for electricity.
Where in your apartment would those wires route through the
walls? Combine those possibilities with where your monitor
does and does not shake. Again, no witchcraft. Your analysis
should answer these questions up front.
Without eliminating these most common reasons for shaking,
then everything done afterwards is akin to speculation -
better called witchcraft. Classic reasons for a shaking
monitor are external magnetic fields or an unstable (and
failing) power supply inside that monitor. Ignore everything
else and first deal only with these concepts - these
questions. Be concerned about things that create external
magnetic fields. You are concerned that all utilities are
properly earthed together at the service entrance - which
means suspect how cable was installed. Get that surge
protector completely out of the analysis since mention of a
surge protector here only adds 'witchcraft' to the analysis.
Remove that surge protector completely in all tests.
Monitor will shake now and not shake one half hour later
when the neighbor's electric hot water heater powers on and
off ... which is why your analysis should include a list of
building electric appliances. We still don't even know what
heavy appliances are major electric consumers meaning we still
don't even have basic facts.
What is creating magnetic fields? Stop worrying about myths
such as 'connect this wire and sometimes the shaking is
less'. Either the shaking is significantly eliminated or you
are grasping at straws. Where does the monitor work without
shaking? What happens when monitor is powered in another
building, or is powered outside on the lawn connected to a 50
foot extension cord - where external magnetic fields would not
exist? Get facts. Determine if external magnetic fields, a
failing internal power supply, or even improperly connected
utilities to the building create your shaking. Until you have
eliminated the classic and major reasons, then everything else
posted only creates confusion.
Notice the engineer's "break the problem down into parts and
then attacking each part with smart bomb precision". Go after
each classic reason and completely ignore other
possibilities. Either it is or it is not external magnetic
fields. Ignore everything else until that and only that
question is answered with a definitive yes or no. Only then
are we ready to consider the next in a list of possible
reasons. You are not breaking the problem down into parts AND
you are adding witchcraft (that surge protector) to the mix.
"John H." wrote:
| Quote: | Well, I am not sure how much I can verify as it's an apartment,
and I cannot rip up things to check on things:)
As far as moving things, when I did move both monitors and
computer to other side of the room, yes the shaking seemed
to mostly go away, unless I plugged coax surge protector into
coax on wall and had grounder cable connected, even though
nothing was connected to surge protector!
however, it seems like sometimes the monitor shakes more than others,
any ideas? |
|
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|
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Jasen Betts
Guest
|
| Posted:
Sun Sep 18, 2005 3:26 pm Post subject:
Re: due to some kind of interference, monitor display is "sh |
|
|
On 2005-09-16, w_tom <w_tom1@hotmail.com> wrote:
| Quote: | The only device that would be effective on the cable was
something that galvanically separates the cable from the
household appliances. IOW something containing a transformer
- not a filter.
|
I've seen TV antenna isolators that just used capacitors.
but yeah it could be done with a tranformer - a single turn
for each winding on a UHF-rated balun core would do it.
Bye.
Jasen |
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John H.
Guest
|
| Posted:
Wed Sep 21, 2005 12:35 am Post subject:
Re: due to some kind of interference, monitor display is "sh |
|
|
ok here is the problem now. The cable guy came the other day, and
after plugging my power into his generator, we observed that the
shaking had gone away, and i no longer had a "hum" on my tv card
display, or rising horizontal bar.
So we told this to the electrician, who came today.
he said the following
"unable to fix cable line problem. new grounds run, all
connection tightened. I did find a loose neutral in main panel and
fixed it"
yet the problem remains! Now I am waiting for the cable people to
come back, but I am almost positive it's some electrical thing, or
something.
Even when I disconnect from coax on wall, my monitor is still
shaking.
what can i do now? |
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Ken Taylor
Guest
|
| Posted:
Wed Sep 21, 2005 12:35 am Post subject:
Re: due to some kind of interference, monitor display is "sh |
|
|
"John H." <mistamaila@nospam.gmail.com> wrote in message
news:pan.2005.09.17.19.46.20.824522@nospam.gmail.com...
| Quote: | On Sat, 17 Sep 2005 09:03:19 +1200, Jasen Betts wrote:
On 2005-09-09, John H. <mistamaila@nospam.gmail.com> wrote:
hi, I have two monitors connected to my ati card.
I have
coax on wall - > cable modem surge protector (very small
-> 2- way splitter -> cable modem
-> tv card on pc
there is a line off the surge protector which goes into screw
in order to ground it.
OK, so there are several weird situations from this. If I have
coax from splitter to TV card, and I do not ground it to wall
outlet, both monitor displays shake REALLY heavily. If I ground
it to wall outlet, large 19 inch CRT shakes some, but not nearly
as much(where I am at now).
Now, if I move computer and two monitors to other side of room
with no peripherals attached, no shaking. If I simply plug the
surge protector into the coax on this side of the room, and ground
is connected, even though NOTHING Is connected to surge protector,
on the clear other side of the room, both monitors begin shaking!
I think the surge protector is causing a ground loop in your coaxial
and/or mains cable.
to reduce this effect possible move it closer to the service
entrance for the electricity and cable. that way the loop will
exist mostly outside your dwelling and thefore the electromagnetic
effects of it will bereduced.
how do you mean "Service entrance".
It's a small apartment, but the other one I was at was smaller
and i got rid of the "shaking" there.
I did, however, order a new UPS, so I don't know if that will help.
If I remove the coax surge protector, it seems to sometimes
be worse.
|
So what did you do at the other place to get rid of the shaking?
Ken |
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