Lightning and modems


K

KenK

Several years ago, my built-in dial-up modem was evidently damaged by
static electricity from a nearby lighting discharge. Anyhow - it no longer
worked and I had to get an external modem. Since then I always unplugged
the phone line from the modem during stormy times or when the computer is
not in use. Normally I don't use the computer if thunder is in the area.

Now I have DSL. Should I unplug the phone line from the CenturyLink C1000A
modem as I did with the other or is it protected? Anyone know? Or found out
the hard way?

TIA
 
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P

Paul

KenK said:
Several years ago, my built-in dial-up modem was evidently damaged by
static electricity from a nearby lighting discharge. Anyhow - it no longer
worked and I had to get an external modem. Since then I always unplugged
the phone line from the modem during stormy times or when the computer is
not in use. Normally I don't use the computer if thunder is in the area.

Now I have DSL. Should I unplug the phone line from the CenturyLink C1000A
modem as I did with the other or is it protected? Anyone know? Or found out
the hard way?

TIA

I would treat it the same as your other modem.

I've looked at pictures of ADSL PCBs, and I
don't "see any magic" on there. It's just as
exposed as a dialup modem.

Paul
 
K

Ken Blake, MVP

Several years ago, my built-in dial-up modem was evidently damaged by
static electricity from a nearby lighting discharge. Anyhow - it no longer
worked and I had to get an external modem. Since then I always unplugged
the phone line from the modem during stormy times or when the computer is
not in use. Normally I don't use the computer if thunder is in the area.


Not using the computer is meaningless. You should unplug it, not just
refrain from using it.

Now I have DSL. Should I unplug the phone line from the CenturyLink C1000A
modem as I did with the other or is it protected?


The risk is exactly the same. Unplug it.

Anyone know? Or found out
the hard way?


Do *not* rely on using surge protectors. Most of them are little more
than fancy extension cords, and offer next to no real protection.
 
P

Paul in Houston TX

KenK said:
Several years ago, my built-in dial-up modem was evidently damaged by
static electricity from a nearby lighting discharge. Anyhow - it no longer
worked and I had to get an external modem. Since then I always unplugged
the phone line from the modem during stormy times or when the computer is
not in use. Normally I don't use the computer if thunder is in the area.

Now I have DSL. Should I unplug the phone line from the CenturyLink C1000A
modem as I did with the other or is it protected? Anyone know? Or found out
the hard way?

TIA

ADSL uses the same 2 wires that your pots line did.
So does VDSL.
Keep unplugging your phone line in storms.
That's what I do.
 
G

gargoyle60

Several years ago, my built-in dial-up modem was evidently damaged by
static electricity from a nearby lighting discharge. Anyhow - it no longer
worked and I had to get an external modem. Since then I always unplugged
the phone line from the modem during stormy times or when the computer is
not in use. Normally I don't use the computer if thunder is in the area.

Now I have DSL. Should I unplug the phone line from the CenturyLink C1000A
modem as I did with the other or is it protected? Anyone know? Or found out
the hard way?

TIA

Basic surge protection offers only limited help regarding static and EM from lightning stikes.
I've lost one dial-up modem to a nearby lightning stike and had one ADSL router corrupted (luckily I
was able to reset and reconfigure after much effort).

You have to ask yourself if you really want to take the risk and how much /money/time/effort you
want to spend fixing the damage after a lightning stike? Personally, I would prefer to avoid the
hassle and simply play it safe. Your choice.
 
R

RobertMacy

.>...snip...

If you buy decent surge protectors and assure your grounding is good,
there is no reason to ever unplug anything.
I am in the lightning capital of the world and I have not lost
anything in 30 years.

where is 'lightning capital'?
 
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P

Paul

If you buy decent surge protectors and assure your grounding is good,
there is no reason to ever unplug anything.
I am in the lightning capital of the world and I have not lost
anything in 30 years.

I think it's still healthy to ask the question, of whether
certain types of surge protectors affect ADSL. That isn't answered
here, but at least someone asked the question.

https://community.bt.com/t5/ADSL-Co...rge-suppressor-affect-my-BB-speed/td-p/375299

The original phone network, only has to pass 4KHz, and so impairments
to the line are allowed to be different, than they would be if attempting
to pass a megahertz baseband signal (2.2MHz on ADSL2+).

In the pictures here:

http://www.kitz.co.uk/adsl/btsockets.htm

the BT main plate uses something I don't recognize.

http://www.kitz.co.uk/adsl/images/phone/components.png

Is that a gas tube ? It looks too thick for a MOV.

One difference between their phone system and ours,
is their ringer signal is carried on a third wire. Whereas
our ringer is HV AC carried on the line pair.

*******

If your modem is capable of reporting line statistics,
you can compare performance (noise margin) with and without the surge
protector in place, and see if it makes any difference.

I worked with an engineer, who was tasked with putting
surge suppression on an Ethernet interface (higher frequencies
than ADSL), and his comment at the time was that it
was pretty difficult to find a protection device that
didn't degrade return loss. He was experimenting with a
semiconductor device, which has two devices in series
inside, the first device with a very low junction capacitance,
the second device more robust. And the combination was
intended to keep capacitance down to the picofarad level.
But the device probably doesn't have all that high a surge
rating. I didn't look at all the details at the time,
but at least noted there was yet another flavor of
protection available.

*******

So I plugged return loss into the search engine, and found this
article.

http://www.epanorama.net/newepa/2012/07/30/adsl-overvoltages-and-protection/

And rather than worry about the details, all I can say is
you'd want to do a noise margin test with and without the
surge protector in place, to see if the surge protector
might be the wrong type.

Paul
 
K

Ken Blake, MVP

If you buy decent surge protectors and assure your grounding is good,
there is no reason to ever unplug anything.


I completely disagree. First, note that a decent surge protector is
expensive, the better part of $100. Those that are around $15-25 are
useless junk.

Second, even the best surge protector can do nothing more than
substantially reduce the risk. It can not eliminate it. The only way
to eliminate risk entirely is to unplug.

And by the way, the best kind of surge protector is a whole house
surge protector, not any of those that go between the computer and the
electrical outlet.

I am in the lightning capital of the world and I have not lost
anything in 30 years.


That's like saying. "For the last 30 years I have worn a seat belt
when driving my car, and I haven't been killed yet."

Consider yourself lucky.
 
R

RobertMacy

And rather than worry about the details, all I can say is
you'd want to do a noise margin test with and without the
surge protector in place, to see if the surge protector
might be the wrong type.

Paul

I've designed systems that pass beyond 1GHz, and keep out 50kV trash. Just
have to make the protection system a 'design' [I could find nothing nearly
as good off the shelf.]

The aforementioned design only had to protect the electronics. Another
such protection design REQUIRED passing the 1MHz+ data WHILE being zapped
AND still meet full product's communication specs! That design was more
challenge.
 
R

Rodney Pont

One difference between their phone system and ours,
is their ringer signal is carried on a third wire. Whereas
our ringer is HV AC carried on the line pair.

It is in the BT system. There are only two wires from the exchange, an
RC network in the master socket spits out the ring signal to the ring
wire. Thus the third (ring) wire is only present in the premises and
even that is not needed with modern equipment since they extract the
signal internally. With ADSL in the UK it's often recommended to
disconnect the ring wire at the master socket to get less noise.
 
R

RobertMacy

Central and south Florida
We have a thunderstorm every day in the summertime and some will have
flash bang strikes several times (the time between flash and bang is
virtually imperceptible)
I had the lightning rod on my weather station hit several times. Once
I lost a serial card in the PC that runs it. After fixing the surge
protection on that line, the worst that happened is I needed to reboot
the PC.
...snip...to keep Aioe happy

I was going to guess Florida!

I was there inone of your summer storms and remember many flash/bangs!

All your constructions sounds good! I agree about 'should be able to keep
operating' attitude. just a matter of understanding the principles and
designing for them.
 
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K

Ken Blake, MVP

Somewhat true


If you never took it out of the box it would last forever. Are you
going to rush home from work to unplug everything?


No. First of all, I'm retired these days, so I don't have to rush home
from work. Second, when I was working, and even now, when I'm not, if
I was leaving the house for any length of time, if thunderstorms were
forecast, I would unplug before leaving. And regardless of forecasts,
if I were leaving for multiple days, I would unplug before leaving.

That is just the first line of defense, not the whole solution


That's fine. I don't disagree with that point of view.
 
B

Buffalo

"Ken Blake, MVP" wrote in message
No. First of all, I'm retired these days, so I don't have to rush home
from work. Second, when I was working, and even now, when I'm not, if
I was leaving the house for any length of time, if thunderstorms were
forecast, I would unplug before leaving. And regardless of forecasts,
if I were leaving for multiple days, I would unplug before leaving.




That's fine. I don't disagree with that point of view.

When I leave for a long period of time, I not only unplug the power cord to
the computer, I also unplug the Cat cable from my computer, just in case.
Is it necessary even though I have an APC Battery Backup with built in
suppressors, I don't know, but I feel better that way. :)
 
K

Ken Blake, MVP

"Ken Blake, MVP" wrote in message


When I leave for a long period of time, I not only unplug the power cord to
the computer, I also unplug the Cat cable from my computer, just in case.
Is it necessary even though I have an APC Battery Backup with built in
suppressors, I don't know, but I feel better that way. :)


Necessary? Perhaps not. Safer? Definitely!
 
R

Rodney Pont

When I leave for a long period of time, I not only unplug the power cord to
the computer, I also unplug the Cat cable from my computer, just in case.
Is it necessary even though I have an APC Battery Backup with built in
suppressors, I don't know, but I feel better that way. :)

A few years ago we had a lightening strike near to us and every switch
port and system on a north/south running cable blew while those on the
west/east running ones survived. In August this year it was the
opposite where the west/east running cabled ports blew. So I'd say it
is worth doing if you are happy to do it but I don't unplug. An 8 port
gigabit switch isn't expensive and I've usually got a spare PCI network
card. I buy 8 port switches even though I only use about 4 ports and it
might take 20 years for me to loose 4 ports because it is a rare
occurrence.
 
B

bud--

No. First of all, I'm retired these days, so I don't have to rush home
from work. Second, when I was working, and even now, when I'm not, if
I was leaving the house for any length of time, if thunderstorms were
forecast, I would unplug before leaving. And regardless of forecasts,
if I were leaving for multiple days, I would unplug before leaving.

Excellent and reliable information on surges and surge protection is
available from the IEEE:
http://www.lightningsafety.com/nlsi_lhm/IEEE_Guide.pdf

A simpler guide aimed at the unwashed masses is available from the NIST:
http://pml.nist.gov/spd-anthology/files/Surges_happen!.pdf

What gfretwell has written is consistent with both guides (except I
don't think they include ferrite cores).

I don't think 'unplugging' is in either of them. Lots of places in high
lightning areas have equipment that is not practical to unplug and the
equipment survives - protection is not that difficult. But do what you
want. If you unplug, you probably need to unplug everything, including
phone, ....
That's fine. I don't disagree with that point of view.

The IEEE and NIST include both service panel and plug-in protectors.
(Also electrical system earthing, and connecting all wiring to the house
through entry protectors that are connected with a short wire to a
common bonding point on earthing system. Coax ground blocks do not
provide surge protection.)

When using plug-in protectors, all interconnected equipment needs to be
connected to the same protector. External connections, like coax also
must go through the protector. As explained in the IEEE guide (starting
page 30) plug-in protectors work primarily by limiting the voltage from
each wire to the ground at the protector. To do that all wires must go
through the protector.

The NIST surge guide suggests that most damage is from high voltage
between power and signal wires.

The author of the NIST surge guide looked at the energy that could be
absorbed in a plug-in protector using US wiring systems. Branch circuits
were 10m and longer, and surges were up to the largest with any
reasonable probability of occurring. The maximum energy was a
surprisingly small 35 joules. In 13 of 15 cases it was 1 joule or less.
(And the largest surges did not produce the largest energy.) Exposure is
less than you probably imagine. Plug-in protectors with much higher
ratings are readily available. High ratings mean long life for both
plug-in and service panel protectors.
 
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N

Norm X

I am in the lightning capital of the world and I have not lost
anything in 30 years.

I live on the Western side of the Salish Sea (not Salton Sea) and no one
remembers lightning nor static electricity. I guess the salt air is a good
conductor.
 
P

Paul

Norm said:
I live on the Western side of the Salish Sea (not Salton Sea) and no one
remembers lightning nor static electricity. I guess the salt air is a good
conductor.

Then what's this fuss all about ?

http://www.kp44.org/LightningProtectionABYC_Standards.php

Same sort of practical advice.

http://l-36.com/read_html.php?file=...protection&title=Boating Lightning Protection

I have to laugh at this section.

"You are two miles from shore. The thunderstorm which is
now five miles away is traveling in your direction at
20 miles per hour, which means it could be overhead within
15 minutes. Can you reach shore--two miles away--and seek
shelter within that time? You better move!"

And the following is what happens if you don't check
your weather radio.

*******

Just sit right back
And you'll hear a tale
A tale of a fateful trip,
That started from this tropic port,
Aboard this tiny ship.
The mate was a mighty sailin' man,
The Skipper brave and sure,
Five passengers set sail that day,
For a three hour tour,
A three hour tour.

The weather started getting rough,
The tiny ship was tossed.
If not for the courage of the fearless crew
The Minnow would be lost.
The Minnow would be lost.

The ship set ground on the shore
Of this uncharted desert isle
With Gilligan,
The Skipper too.
The millionaire
And his wife,
The movie star,
The professor and Mary Ann,
Here on Gilligan's Isle.

Paul
 
B

Buffalo

"Paul" wrote in message news:[email protected]
Then what's this fuss all about ?

http://www.kp44.org/LightningProtectionABYC_Standards.php

Same sort of practical advice.

http://l-36.com/read_html.php?file=...protection&title=Boating Lightning Protection

I have to laugh at this section.

"You are two miles from shore. The thunderstorm which is
now five miles away is traveling in your direction at
20 miles per hour, which means it could be overhead within
15 minutes. Can you reach shore--two miles away--and seek
shelter within that time? You better move!"

That link also says: " This potential may be as much as 100 million volts.
To help you understand the magnitude of this voltage, the voltage needed in
an automobile to cause a spark plug to fire is only 15 to 200 volts! And the
spark plug gap is but a fraction of an inch! "
15 volts will not jump a normal spark plug gap and neither will 200 volts.
Most of the time the voltage is well above 10,000 volts.
Just makes me wonder how knowledgeable the author is on the high voltage and
amperage of lightning. :)
Ah yes, Gilligan's Island. :)
 
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B

Buffalo

"Buffalo" wrote in message news:[email protected]
"Paul" wrote in message news:[email protected]

That link also says: " This potential may be as much as 100 million volts.
To help you understand the magnitude of this voltage, the voltage needed in
an automobile to cause a spark plug to fire is only 15 to 200 volts! And
the spark plug gap is but a fraction of an inch! "
15 volts will not jump a normal spark plug gap and neither will 200 volts.
Most of the time the voltage is well above 10,000 volts.
Just makes me wonder how knowledgeable the author is on the high voltage
and amperage of lightning. :)
Ah yes, Gilligan's Island. :)

But, once the air is ionized, then it might only take the low amt of voltage
to continue the arc. Perhaps that is what he was talking about.
 

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