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how far away does a storm have to be

winnipeg1823
Grafter
Posts: 156
Registered: 08-08-2007

how far away does a storm have to be

Once last month, and again for the last two days I have lost, on a regular basis my adsl connection, so much so its impossible to use the internet. The adsl light will go out, come back, then go off again.

On all occasions, when you turn on the car radio there is interference from lightening, so Iam guessing thats what is causing my problem, but there is never a storm overhead, so how far away can it be to affect my connection
6 REPLIES
Plusnet Staff
Plusnet Staff
Posts: 12,169
Thanks: 18
Fixes: 1
Registered: 04-04-2007

how far away does a storm have to be

Hi,

I don't know if there's a scientific answer, there probably is. I'd have thought the storm doesn't have to be overhead to cause interference, it could be anywhere between you and the exchange and then probably can have an effect from a few miles away.
Community Veteran
Posts: 38,215
Thanks: 913
Fixes: 54
Registered: 15-06-2007

how far away does a storm have to be

Of no particular relevance - this is what happened to my connection with a thunderstorm about 2 miles away and most of the cables are underground
Plusnet Staff
Plusnet Staff
Posts: 12,169
Thanks: 18
Fixes: 1
Registered: 04-04-2007

how far away does a storm have to be

I always notice a fluctuation in the SNR during a storm. It normally sites around 10-11dB but can drop to 5 or 6dB as the storm gets closer. You can see when a storm's coming where I live and the SNR will start to fluctuate before the storm is visible.
alanPN
Grafter
Posts: 27
Registered: 01-08-2007

how far away does a storm have to be

I'm not an expert in lightning but do know a bit about radio communications.

A storm cloud (even with no lightning) can induce voltages on power and telephone lines. Exchange equipment takes care of it, as does the surge arrestor in your telephone master socket, since the current is miniscule.

A lightning bolt will also induce voltages on nearby telephone lines. The induced current here is greater, and is a sharp but very short pulse.

That pulse will cause a router drop out or if a bolt is close enough will fry your router as the surge arrestors would be overwhelmed. Distance depends on the size of the bolt, the telephone cable length, other paths to earth etc. It's unpredictable as far as I'm aware, but clearly the closer the bolt the higher the risk.

Lightning activity also produces radio frequency energy that affects an ADSL signal. This could be from as far as 100 miles away, but more likely to be in the range of 10 to 40 miles for the RF frequencies involved. That is why SNR drops when storms are about - the general RF noise level on the telephone line goes up.

Underground cables are not immune as the RF at these frequencies is ground penetrating for a short distance.

However, there are too many variables and even the professional experts cannot predict all of this!
kitz
Rising Star
Posts: 817
Thanks: 46
Registered: 08-06-2007

how far away does a storm have to be

>> but there is never a storm overhead, so how far away can it be to affect my connection

Entirely depends upon the strength of your signal and your individual line stats to begin with.
The further away from the exchange you are then your adsl signal is obviously not going to be as good as someone who lives near the exchange.

The other night there was a pretty good storm going on a several miles south of here. (at a guess about 10-20-30 miles). My desk at is in front of a window that looks south (and out at the exchange) and I was sat watching it only by the light of my monitor.. but also watching my router stats at the same time.

Every flash of lightening without fail caused my Errored Seconds count to increase by 1. The nearer flashes of around 10 miles away also caused the CRC errors to start racking up.

Please do NOT try doing what I did. Its NOT recommended the only reason I did was because the storm was in the distance and not direct overhead.. and Im on a very short line (7db) to the exchange which is all underground cable.
My reasoning is that I could have been out that night anyhow and my router is always on 24/7 (yes its surge protected). If I had of been out then I wouldnt have been able to turn it or my pc off. If the storm had been nearer then yes I would have.
N/A

how far away does a storm have to be

On three occasions I've lost equipment to lightning strikes nearby. The first was before I went broadband, then later I had the phone port on an antisurge astrip burnt out (worked though, no further damage) and the third time went straight through the protection, took out a router, hub, development system and PC com port.