Storms and broadband speeds

Can storm/lightning effect broadband speeds? Noticed that during the last few storms we have had over the past few days, my speeds have been abit erratic (usually get 8mbps but can be anywhere from 5-8 during speedtests). Soon as the storm passes the speeds become consistent again.

During the storms my connection remains stable, SNR remains fine, pings etc although do get more corrected CRC errors.. Wonder if the electricity in the air causes issues or something?

Edited by bobble_bob (Sun 05-Jul-15 17:20:57)

In reply to a post by bobble_bob:

Can storm/lightning effect broadband speeds? Noticed that during the last few storms we have had over the past few days, my speeds have been abit erratic (usually get 8mbps but can be anywhere from 5-8 during speedtests). Soon as the storm passes the speeds become consistent again.

During the storms my connection remains stable, SNR remains fine, pings etc although do get more corrected CRC errors.. Wonder if the electricity in the air causes issues or something?

Yes, the electrical discharges are picked up by the copper pair and will appear as noise on the line. Change might be just a dB or so or it could be 20 or 30 dB (or more). Results in short term changes to the noise margin which can effect the sync speed and it will appear erratic.

The connection does remain synced so that is the same, its the actual throughput that changes aswell as the CRC error count. Is that what you meant with "effect the sync speed and it will appear erratic"?

Yes, at the extreme you could get a full resync - a close by lightning strike for example. Up to that point it could change the max throughput, actual throughput, error counts ... and potentially cause intervention and interleaving to be applied.

Cheers for that. Having run a few more speedtests after the storm has cleared things appear to be back to normal, and the error count is as it was before the storm

Thanks for the help

Around 10 years ago when I had 1.5-2Mbit ADSL, there was a summer storm. I was graphing the SNR figure and errors on the line at this point. Several hours before the storm arrived (well before there where any visible signs), the error rate on the line began to increase. I was watching the graph in real time as it happened, and initially, I was slightly perplexed as to what was happening (because I had not graphed anything like this to date). When the storm arrived, several re-syncs happened and the sync speed dropped. After it passed, I waited a few more hours and then forced a re-sync and everything was back to normal again.

So yeah, that was first hand experience of an electical storm with DSL technology. I probably should have been a bit smarter and unplugged the router for the duration, but it was fine in the end.

AM radio is loved because of its range and thus no surprise that bursts of noise travel a long way.

VDSL2 frequencies generally are slightly less range, but would be no surprise to see similar effects.

I wonder how far away storms can be to effect your connection? A few week ago i posted in this forum about flutuating speeds and a resync for no obvious reason. At the time there wasnt a storm where i lived, but maybe somewhere along the line there was

Does not even have to be above the line, if you remember the days of AM radio listening it was common to hear crackling well ahead of hearing the thunder.

I reckon the one I spoke about in my post was hundreds of miles away when I started to see the error count gradually increase on my graph. Then over the space of 2-3 hours, it ramped up and that is when the weather abruptly changed and the storm finally arrived.

Tis all to do with atmospherics, and as MrSaffron said, electrical storms tend to interfere in the AM radio spectrum which will certainly affect ADSL (VDSL maybe not quite as severely), possibly resulting in re-syncs if the interference is bad enough and/or the SNR margin on your line is too low eg. you're syncing at 60/20 (like I was when I had Unlimited Fibre 2 from Zen) and the line is being driven to its maximum speed with no headroom available. This is one of the reasons I dropped back to a 40/10 connection; I have a better SNR margin (more headroom) so the line is less susceptible to noise/interference.