Kitz Forum
Broadband Related => ADSL Issues => Topic started by: Weaver on January 15, 2020, 09:33:04 AM
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Two lines
down so I thought at the time, wrongly, after close strike less than 1km away just above the north shore of Loch Eiseort, to the east of Heasta between here and Druim Fheàrna. Did not unplug lines in time so some kit was broken. Was running on 3G firebrick failover instead in the night.
AA support was emailed, thinking there were two lines down.
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I wonder how many times they have to fix your lines before FTTP suddenly seems affordable for them? ::)
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Google maps tries to get one out of two correct . . . as it shows "Loch Eishort" and "Drumfearn".
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Google maps has located the anglicised forms. Eishort is as something+"fjord" where the initial f is deleted according to the rules of Gaelic grammar. Not sure what the first element is, perhaps "ice"+"fjord" ?
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Contacted AA who couldn’t find any problem with the lines - that’s because it turned out that the problem was at our end. Two modems : 2, 3 - were slightly cooked - replaced the modems and an Ethernet cable and all was well.
The ethernet cable between modem #3 and the 8-port VLAN MUX/DEMUX switch was on inspection sooty, blackened. Luckily however, the 8-port MUX switch itself seems fine, does not seem to need replacing. Although somehow this time the mux escaped, this has once again set me I’m thinking I ought to have a spare. Alternatively, if a MUX got blown up, AA could send me another one and I could live on three modems and with a VLAN-free XML config in the Firebrick until it came. The ports in question on the mux did not seem cooked, just the ethernet cable so it seems that the 0.5m cat7 patch cable seems to have had some resistance perhaps.
Two ‘new’-ish VMG 1312-B10A modems were programmed with my preferred ‘Johnson’ firmware load, and the correct XML config file for each modem in the appropriate slot (slot #2 or #3) was generated and pushed into the modem concerned. A short CAT-8 patch cable was put in in place.
Modem per-slot # config :: I have an iOS Shortcuts program that generates the correct XML config file for slot #n and pushes it into the iOS Textastic text editor, an XML cfg file with an appropriate filename that includes the date and slot <yyyy-mm-dd>-m<slot>.cfg.xml all ready for me to just hit Save and to upload the cfg XML file into the modem once it has been configured with the right firmware.
(https://i.postimg.cc/FRGV5DbJ/644-B72-FD-AD32-471-A-B841-8492-E76457-EE.jpg)
Blackened ethernet cable to modem 3; both ends were similar
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I had wondered if ethernet surge protectors are actually any good? Sounds like its something that could be worth looking into.
Very curious that it didn't damage anything further up, although some hardware I believe have built-in surge protection so maybe that's why?
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I have not tried ethernet surge protectors before. I would need four of them.
I had thought about getting four pairs of fibre-media-convertors. Bit of a nightmare tho.
I have decided to order a spare VLAN MUX switch; at least that stands in front of the Firebrick. I blew a port of a Firebrick FB2700 and AA gave me a replacement free of charge, incredible ! I just contacted them to ask about costs of repair for an insurance claim on the damage and got a new unit and a warranty extension too!! If my current Firebrick FB2900 blows up now, I have my spare Firebrick FB2500 which went back into service when the first FB2700 was damaged.
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I was thinking along the lines of four xDSL to optical media converters, a "four to one" optical mux/demux and then to the Firebrick FB2900 via the appropriate SFP transceiver. :-\
Any high voltage zap on the metallic pathway would have the potential to "take out" a media converter but the equipment further downstream would then be protected by the optical fibre.
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I would like to see a picture of that. Your proposal avoids the need to convert with four pairs ?
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I suspect that the xDSL to optical media converters may be difficult to source. Four would be required, each one to take the place of a ZyXEL VMG1312-B10A.
The "four (or more) to one" optical mux/demux should not be too difficult to source, likewise the SFP transceiver for the Firebrick FB2900.
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I’m sorry to be so dim. I thought I had found a mention of a device that would just convert gigabit Ethernet copper into fibre optics and then this paired with another similar device could do the reverse conversion. But that device would not replace a B10A, just be added on to it ?
An optical mux/demux - I am learning something.
I would prefer not to have a solution that used the SFP port, because if I did, then the config would not work on the fb2500 which I use in an emergency.
I have a program that converts fb2900/2700 XML inti FB2500 by preprocessing it and spotting special significant comments and replacing some sections with marked alternatives. This is in order to handle the lack of a USB ‘dongle’ 3G NIC interface. These markers are like #if / #else in C. The default unpreprocessed xml is legal ready to rock-and-roll fb2700/2900 code which does not need any processing to make it legal as all markers are hiding inside special decorated comments. The code that is in for-fb2500 alt-blocks is all inside commented-out wrapper markers so it’s invisible normally and is exposed when converted to fb2500 mode.
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I’m sorry to be so dim. I thought I had found a mention of a device that would just convert gigabit Ethernet copper into fibre optics and then this paired with another similar device could do the reverse conversion. But that device would not replace a B10A, just be added on to it ?
A pair of Planet GT-802S (single mode fibre) or a GT-802 (multi-mode fibre) media converters (per line) would do exactly what you have described. But as you have four lines, that setup would require another eight PSUs to be mains powered! :swoon:
The more I think about it, the more I am convinced that my suggestion of an xDSL to optical media converter does not actually exist. (xDSL to Ethernet media converters and Ethernet to optical media converters do exist.)
Ideally you need four passive opto-isolators in between the four NTE5s and the four ZyXEL VMG1312-B10As. Again, I am uncertain if such devices actually exist.
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I can’t help wondering if a carefully designed surge protection strategy might be more cost-efficient, rather than a hybrid electronic/fibre solution, the electronics of which would still be vulnerable, and still break the broadband connection?
Obviously, domestic surge protection won’t save you from a direct lightning strike. But my understanding is, most of that sort of damage is likely to be caused by stray currents from relatively distant strikes. And my understanding is, these sorts of surges are manageable, with good design.
I’m not sure a lot of the readily available surge protectors really do any good, ‘snake oil’ often springs to mind. But functioning technology does exist, witnessed by the fact the electronics in BT exchanges is not nearly so susceptible to damage from indirect strikes...
As to who might produce or advise on such ‘good design’, not me. Most of the things I once knew about good electronics design have long been filed in my grey matter under the category ‘forgotten’. :D
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Good advice from 7lm. The damage I have had a-plenty over the past twenty years has I believe been from either stray induced currents or else GPR/EPR - something that people forget about all the time. With such a long line I would suspect that GPR/EPR is a serious danger and I would think that it brings on slow cooking rather than dramatic damages.
As for direct lightning strike, I have several enormous trees right near the house; I would think they act as lightning conductors and I would expect them to be much more tasty for a direct close strike.
I would need to find some serious engineer with a reputation backed by evidence who could arrange what - gas discharge tubes? - for the dsl lines and for the mains. It would probably cost a fortune.
My current strategy - no pun intended- warning system hardware,
- warning app for iOS and real-time lightning map
- spares
- proper insurance.
- mains surge protectors
I have two warning systems and maps (i) a Skyscanner hardware lightning warning system with a range of about 120mi or so; it’s ridiculously sensitive which is very good as it gives you hours of warning to check maps if strikes. The only bad thing about it is that I can’t seem to get the beep sound alert to work. It flashes lots of bright lights.
(ii) The second warning system is an iOS app "Lightning Tracker Pro" which warns me of strikes in a particular chosen radius and displays a real-time updating map. The app is running on two iPads now it give me a better chance of hearing / seeing the alert notifications. (iii) I also have a web-based strike map at lightningmaps.org and blitzortung.org. I know these things work because I can check the iOS Apps against the web maps and against the hardware SkyScanner unit and I can hear the thunder at the correct time according to the sound arrival radial picture in the optional blitzortung thunder map.
Mains protection: lots of surge protectors based on the fattest MOVs I can find expensive Belkin audio-video units and also a pair of UPSs which are supposed to provide surge protection.
With spares there is no downtime, and serious insurance removes the financial shock. I have more than a complete set of replacement spare modems, I have a second small mux switch on order should be here On Saturday and I have a spare Firebrick.
I have checked that our insurance covers lightning damage and once began to make a claim but never went through with it as that was the time that AA gave me a free replacement Firebrick FB2700. So the insurance is thus far untested.
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I would need to find some serious engineer with a reputation backed by evidence who could arrange what - gas discharge tubes? - for the dsl lines and for the mains. It would probably cost a fortune.
The first requirement, before any other devices are installed, would be a low-impedance (i.e. sub one ohm) ground (earth) connection. I suspect that some serious rock drilling would be required for the installation.
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The house is earthed by PME.
As for a sub-one-ohm site, I wonder about using the stream immediately below the house. What about burying a large copper plate in the stream, or in the damp soil in the bank by the stream?
Below the house there is an aquifer into which we with the help of my neighbour Niall have drilled a deep borehole. Water comes down from Beinn nan Càrn and we exploit the limestone layer deep below the house which by the way emerges on the surface on the far side of the public road to the north east of the cattle grid (the one on the public road, not the one on our drive). I don’t know anything about it but I wonder if it would be effective to just drop a serious conductor down the borehole?
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As for a sub-one-ohm site, I wonder about using the stream immediately below the house. What about burying a large copper plate in the stream, or in the damp soil in the bank by the stream?
Hmm . . . I'm not qualified in the field but "tingles in the whiskers" are hinting that would not be appropriate.
One other thought: I wonder if it would be possible to engage the services of the relevant division of the BT Group to install, at the Weaving Shed, identical protective devices as that installed within an exchange building?
Perhaps licquorice, 4candles or Black Sheep may have an idea as to what would be required?
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I know I said I’d forgotten most of this stuff, but if a common-mode spike appears on the phone lines, a surge protection impedance of many hundreds of ohms might be beneficial compared to being presented to a completely ungrounded modem. ???
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Sorry 7LM, could you clarify? I have a Theoretical Physics degree so I am semi-literate in things electrical. (The "theoretical" does not help here, :no: :no: :no: :'(
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I’m not trying to portray myself as an expert in this and in fact I never have been. But my take is this....
When a nearby lightning strike causes a nasty spike to appear in the phone lines feeding my modem, I reason it will be common-mode, ie both conductors will see the same spike with same polarity. Since my modem appears to be ungrounded, that spike will simply pass through the modem (possibly destroying it) before heading out into the ethernet cables, repeating the process at my router etc, trying to seek a path to ground.
My possibly flawed understanding is that whilst lightning is a complex energy phenomenon, at the manifestation point of contact above, it behaves as a current source. A fixed current will flow in passing the spike to ground, regardless of the resistance to ground. In order to satisfy Ohm’s law, the greater the resistance, the greater the voltage across the path. If the current can find no convenient metallic path, even if it is a relatively weak current, it will create a very high voltage in the form of a spark, and that may be what causes damage.
I’m not convinced these currents are necessarily very high (we’re not talking of a direct strike), so
I would assume that a path to ground comprising a few hundred ohms would still be preferable, compared to the ‘fresh air’ between my modem input and ground.
Repeat again I am no expert. Would be fascinated to be corrected on above thinking. :)
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Interesting discussion of phone wire lightning problems here...
https://www.britishtelephones.com/lightng.htm
It’s quite an old article and he describes NTE5A gas discharge tube 11B as a ‘waste of time’ in the context of lightning protection, suggesting it be replaced in problematic areas with tube 21A, which is 3 pole and can be earthed.
I found this tech spec for said 21A...
https://assets.mayflex.com/downloads/EXCEL/E0206-S-Exc-21A.pdf
Unfortunately I vaguely recall (confirm/deny, anybody?) that even the ‘waste of time’ 11B is no longer fitted as it impeded broadband signals. If true then I would imagine same would apply to 21A, though my hunch is that the stated capacitance (max) of 5pF wouldn’t be massively detrimental.
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What do they have at the exchange end?
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What do they have at the exchange end?
That's what I hope either licquorice, 4candles or Black Sheep may be able to explain.
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What do they have at the exchange end?
My hunch would be that to protect a telephone exchange, a bottomless budget would be spent on the maximum possible lightning protection, with exotic earthing arrangements starting with the fabric of the building itself. I’m not sure it would be economically viable, or even possible, to replicate that at subscriber end hence alternative, compromised solution, might be more appropriate.
That's what I hope either licquorice, 4candles or Black Sheep may be able to explain.
Indeed, such advice would be welcomed. :)
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I emailed AA and asked if BT could be employed to fit lightning protection; not surprisingly the sales manager replied that it isn’t something BT will sell. BT just fixes it when it gets wrecked again and again.
There’s nothing stopping me spending a fortune of my money on protection at a point on my side of the border, beyond BT-Land.
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I emailed AA and asked if BT could be employed to fit lightning protection; not surprisingly the sales manager replied that it isn’t something BT will sell.
[grumpy mode]
A&A are not the BT Group. What an employee of A&A decides to state is just her/his opinion.
[/grumpy mode]
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You don't need a lightning STRIKE to knock out your equipment. A near miss will do. I would think any earth is worth trying. If you place a wire , or better, a rod down a bore hole may give an earth, provided that the water at the bottom is not pure. But I would have thought lime in the water may solved the conduction problem perhaps.
One place my firm installed some equipment at, had a radio station on the site. Lightning struck the mast, and this we thought knocked our system off. But after a time it was found that the computer type equipment was perfectly safe, but a number of mains operated VDUs were knocked out. When the VDUs were checked out, they were found to have the interfaces blown up. Seems that mains earth and station earth were not bonded sufficiently well to protect against the problem that occurred. Incidentally, all the landline speech band modems were all totally unaffected............
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Our chimney got hit years ago and it took out the answerphone, modem, blew a hole in the IO chip on the motherboard the modem was plugged into (yes it was back in dialup days and I shared dialup across the LAN) and blew the diode of every network card (10BASE2 coax). It also blew the neon in the immersion heater switch.
Interestingly, I was able to reuse those network cards when I moved to a hub as the RJ45 ports were fine, as was all the PCs other the router PC where the spike came in.
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I agree with Benji09 that you don’t need a lightning strike to cause damage, a near miss will do. And don’t forget GPR/EPR, which cooks your hardware when there is no strike, because there hasn’t been a strike.
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Worth mentioning that even if some devices appear to survive an event that damaged connected devices, the surviving devices may still be degraded from factory spec. They may be more vulnerable to the next storm, and/or their performance may be impacted. :'(
Verging off topic a little... A few years ago I had the privilege of witnessing a direct strike on a small passenger aircraft on its landing approach at a regional airport. Really amazing, the zig-zag from the clouds touched the nose while a zig-zag from the tail continued to ground. I momentarily wondered if I was about to witness some awful catastrophe but no, the plane just continued its path and made a normal landing. The plane was immune simply because the lightning currents found no resistance within the metal bodied aircraft. Being presented with no resistance, the lightning simply passed the length of the plane, causing no damage. :)
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Indeed, I'd imagine the reason it so thoroughly fried the IO chip on the motherboard was because it will have jumped to ground within the chip.
Although if the voltage is high enough, it would have found somewhere to do so regardless.
What amazed me though was while it did all that damage, the phone line was completely unaffected. I'm using the same drop wire today.
The most scary part was how it also caused all the phones in the house to ring continuously, like in a horror movie. Apart from the cloud of smoke next to the fuse box. ???
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From all the info available BT/Openreach does not get involved in lightning protection.
There's an interesting article here which seems to imply that as far as they are concerned protection costs more than replacement of equipment.
https://www.britishtelephones.com/lightng.htm
I can't find anything about their own buildings, but I should image they would have some form of lightning rod/ lightning conductor plus surge protection and backup. I seem to recall a few years ago on social media a video of a storm hitting an exchange somewhere up here in the Lancs/W Yorks which someone had filmed from their bedroom window.. iirc the lights inside the building dimmed briefly. I can't find it again now as it was going back several years but if memory serves correct it supposedly hit their (backup) power generator and there was black smoke briefly rising above it :(
It would appear that when it comes to business and workplaces there are regulations in place for Lightning Protection and Compliance and if necessary there are firms such as Voltix (https://voltixservices.co.uk/avoid-the-shock-all-you-need-to-know-about-lightning-protection-and-compliance/) which will carry out risk assessment, and any required installation and maintenance of lightning protections systems. There are also specialist firms who design and implement solutions against lightning strikes and power surges for data and telecom businesses. Obviously though this is over-kill for Weaver.
Back to Openreach telco equipment in the home/office... I found this article (https://www.pddevices.co.uk/news/5-lightning-strike-hits-devon-business) whereby a lightning strike to a substation at a Business Park took out telephony equipment to most of the businesses in the area.... and at the bottom there is a single paragraph about one of the business who suffered little damage due to having their telephone lines protected by these Telecom Line Protection devices (https://www.pddevices.co.uk/products/data-networks-and-telecoms/tlp-series).
In fact on this page (https://www.pddevices.co.uk/products/data-networks-and-telecoms) there is other equipment which may be of interest?
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I did have a further thought about Weaver's earth. Perhaps a 3 metre copper pipe buried in his grass, flat in the ground as deep as it could be put in. I assume the top soil is more than a few inches deep in the garden. I would think that where Weaver lives, there should be plenty of rain to keep it wet. If this is carried out, the connection to the earth wire should thick, and also soldered above ground and painted over, insulated from the weather. Putting the pipe in the ground can be carried out by making a V groove in the soil with a fork and a spade. After the work is finished the soil can pushed back with a foot! Maybe Weaver could get some help with this?
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What’s the best way to connect the earth up to the ‘impact’ sites, the sites from which current needs to be effectively carried away?
If Mrs Weaver can recruit some help for a bit of digging, then we do have some wet soil. Neither she nor I are up to any digging anyway.
I don’t know if electricians would do that kind of work ?
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What’s the best way to connect the earth up to the ‘impact’ sites, the sites from which current needs to be effectively carried away?
Personally I’d say you need to resolve that issue first, before thinking about earth rods. Ie... To what things in/around the home will this earth rod be connected, and how will currents flow from problem points (such as phone wires) towards the earth rod? I remain unconvinced that enhanced earthing will do any good, unless you have a design to address these specific stray currents.
An Electrician would be able to help with earthing of your mains electricity but the purpose of that earthing is to ensure that fuses and other protective devices ‘blow’ when certain dangerous electrical faults develop. That’s different from lightning protection.
Then again, if you’d actually be connecting this rod to anything then you’d be modifying the house electrical earthing, and I’d certainly say you need to consult a well qualified Electrician to ensure your plans comply with current wiring regulations.
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Incidentally if the house earthing system is really PME then the earth potential within the house may be different to the true earth potential away from the house, due to neutral current on the combined neutral/earth conductor.
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Fine advice about the electrician. My house was built in 1934, and uses the original wiring from the street. The earth is taken from the protection screen of the the street cable. Our water pipes in the road, if original, are lead ( hard water area! ), therefore well earthed outside the house anyway. Some of the houses in the road have had their mains supply reinstalled as `PME' supply, which is now the norm for new work. My own internal wiring is PME as is a requirement anyway, although my feed has not changed.
Reference Weaver broadband lines, anything he connects to his phone line is likely to wreck is broadband, and I think BT try to avoid fitting surge protectors for this reason. But, maybe, Weaver's problem could be also due to what get induced onto his mains supply feed, with an earth which is all over the place, making mains surge protectors ineffective. Bear in mind if the BT lines are are referenced to earth at the exchange, and the earth potential at his home is not stable,, then that could cause a problem.
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The earth is taken from the protection screen of the the street cable.
That sounds like TNS, rather than PME.
My own internal wiring is PME as is a requirement anyway, although my feed has not changed.
Not sure what you mean?
Reference Weaver broadband lines, anything he connects to his phone line is likely to wreck is broadband
I had also heard of that effect. But looking at the specifications of a 3 pole GDT device, with max capacitance of 5pF, I’m open minded that it’s just a rumour.
It is the simple fact it is 3 pole device with an earth, even a crappy earth, that makes it hold promise, rather than having no earth at all. Here’s the link (again) to the spec of 3 pole GDT supposedly in BT’s parts box...
https://assets.mayflex.com/downloads/EXCEL/E0206-S-Exc-21A.pdf
And here’s the link to the place that mentioned it, posted by Kitz as well as myself...
https://www.britishtelephones.com/lightng.htm
Ref ‘surge protection’ I think we need to differentiate between those that create a short circuit to protect against high voltages across the phone line, and those that shunt to earth a common mode voltage at the phone lines. The former are pointless when it comes to lightning and the latter require an earth, which (expense) is arguably why BT do not fit them at the subscriber end.
I would still love to know whether BT fit 3 pole GDT (or similar) at the exchange end. Note that protection of “telephone exchanges” is listed as one of the applications of 21A in above link. :)
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I have a friend who is a qualified electrician and runs his own firm. All I need to do is persuade him to come up for a holiday.
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it looks scary but here we dont have any lighting protection installed here in our homes
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Not sure what you mean?
I was wondering that myself, as far as I'm aware the difference between TNS and TNCS (whether or not PME) is only external, whether there are separate N and E conductors in the supply. N and E should be separate on the consumer side in any case. Unless he means his internal bonding is all to the standards required for PME.
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Yes all my internal pipes are bonded to the earth at the meter. Think this is now a requirement whatever your mains feed is. Reference the suppression components on a BT line, I think all types present some form of capacitance across the line. I agree that any simple suppression applied between the pair would be useless. Hence the need for an earth at his site. But that earth should also include the mains earth, since his modems are connected to the mains supply. It is no good if the main earth is floating all over the place, if the BT side of it is not. Perhaps a change to Weavers mains supply to the type normally seen on camp sites where a RCCB is used and a local earth is supplied may be an option. I don't know the official term for it TNK?????. I am not an electrician by trade obviously !
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I am not an electrician by trade obviously !
With respect, I think some of us had guessed as much. :)
Personally I have a BSc in Electrical and Electronic Engineering, though that was many decades ago. Even so, whilst I enjoy tinkering with electronics devices for my own use, and I enjoy speculating on challenges such as how best to protect modems from stray lightning pulses, I would be very unlikely to ever suggest changes to mains supply or earth bonding. That is a topic fraught with danger and way more specialised than a typical Electronics degree course, even if ‘electrician’ may sound like a lesser qualification.
I did have some modifications done to my own detached garage a few years ago, converting the exported PME to TT, but I kept my opinions to myself down and allowed the professional electricians to tell me what should be done, and then allowed them to carry out their work. The other advantage of that approach is they have indemnity insurance, should you need to sue them. ;D
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I was required by the gas company, before I even had central heating installed in my home, to carry out the required earthing. It seems that it is not unknown for the supply company to lose the earth when they make repairs in the road. Also, as I said all new work done to mains supplies is to the `PME' (TN...) standard, so carrying out PME work at the customer's home covers all future safety needs. After I had carried out the earthing work, I was forced to have normal central heating installed due to the hot air system I previously had, could not be maintained any longer.
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I have consigned two modems to the bin. The other two appear fine but I can’t tell. Should I bin them anyway just to be in the safe side? Where safe means reduced performance?
I think not, as the stats look normal. The modems and the MUX switch they were connected to were not earthed. The chain is : four modems, VLAN MUX/DEMUX switch and then the Firebrick router then my main switch, the firebrick is earthed as is the main switch, so I suppose the firebrick would be the exit point if current heading to earth? The firebrick looks fine and the small MUX switch is behaving as normal. I’m getting an additional spare MUX switch. I would think that the very short ethernet CAT6 cable going from modem to MUX which is shown in the earlier image blackened would be reasonably high resistance as it’s such small diameter copper although it is short. The high(-ish) resistance if indeed that’s fair would limit the current - you’re not going to fit 30kA down that wire - although as this was not afaik a lighting strike in the cable, as, according to the map, the nearest strike was about 500-1000m - away I can’t tell exactly - so I assume this was induced current.
I’m surprised that we didn’t get the modems unplugged in time. The modems were unplugged from the wall, just not quite soon enough. I have four additional modems in order, and I have two spares currently I think. It just goes to show that lightning is really unpredictable - when there is any in the area, you could be next - it doesn’t "move", with a predictable behaviour pattern, aside the general wind direction. The areas where there has been no strike are going to be the next source candidates, because they haven’t yet been discharged, so that is why it hops around.
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My understanding is that the momentary currents that flow as a consequence of indirect lightning can be regarded as almost ideal current sources.
That being the case, the current will flow come what may, but the greater the resistance it encounters, the greater the voltage that will arise across the resistor. That is why higher resistances generally result in higher damage. For example a discharge from a cloud to a church spire’s lightning conductor creates a huge voltage and makes a big bang whereas the corresponding current down the spire’s earth conductor is the same current, but creates just a tiny voltage along the length of the conductor, so passes unnoticed.
If the firebrick has a half decent (normal household earth) connection to ground, and has protection devices to provide a safe discharge path from the inputs, that would explain why it survived undamaged.
A modem with an earth connection, but without the input protection devices, would more likely follow the model of ‘cloud to spire’ with a very big flash and bang.
Repeat... just my understanding. :)
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The current source may be ideal but it isn’t necessarily undivided and I think 7LM is talking about lightning strikes rather than induced currents? All such currents have a choice of where to go in some situations; so I would assume that some fraction of the total current takes candidate path A some fraction takes candidate B. We indeed see this division in photos of lightning strikes.
I think 7LM is essentially correct but I think we’re at cross purposes possibly?
If the firebrick and MUX switch are lower resistance than the ethernet cable then we have a potential divider and most of the voltage drop would be in the thin ethernet cable and in the modem, if indeed it is thin enough wire to be of higher resistance.
I wonder why two modems appear ok? Should I get shot of them anyway?
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I wonder why two modems appear ok? Should I get shot of them anyway?
Personally I’d say no, if they seem ok keep using them. But keep an eye on performance and if adverse symptoms subsequently emerge them as well as fixing them, be prepared to attribute the damage, retrospectively, to the storm. That might add data to future cost/benefit analysis of installing protective devices.
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Replacement modems are now down to £15 each - the price has dropped by 70% in the last six months (v approx) as the initial high demand seems to have been dated and more second hand units are coming into the market for some reason. I think new units can still be obtained, but Mrs Weaver will have words me if I buy any more modems than the pile I already have.
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If you replace them now, without waiting to see if they are damaged, you also lose the data for cost/benefit analysis.
I have also recently had my own spending habits reviewed by other half, following unexpected appearance of a bench PSU and umpteen bags of bits for a little project I’m working on. I’ve now been allocated a budget of £x per month beyond which, it seems, written purchase approval will in future be required. :'(
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> I’ve now been allocated a budget of £x per month beyond which, it seems, written purchase approval will in future be required. :'(
Snap. Exactly. I ask my beloved about all substantial planned purchases seeing as I’m not earning anything now and she looks after me. It’s a great thing that modems are so cheap now.
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I haven't been following closely enough, was it discovered the Zyxels on your lines performed better than the HG612?
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In the S.E. where I live, storms are rare. But when I know that a storm is due, I disconnect the ethernet cable from the Sky modem/router, and from the Netgear router in the other room. I then connect between the two via a wireless link for the duration of the storm. I hope by doing this that the only router to be blown up will be the Sky one. Also the Sky router is left floating from earth, apart from any capacity coupling to the mains supply via the double insulated mains supply. Not had many storms were I live to see that my idea does or does not work though.......
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I don’t have a HG612, never tested one. Has anyone tried one on ADSL2 ?
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I don’t have a HG612, never tested one. Has anyone tried one on ADSL2 ?
Yes, way, way back in 2011 (when Asbokid produced the first unlocked firmware image).
First a HG612, then a HG610 and finally a HG622. Subsequently used a VMG1312-B10D and when that went weird on me, moved onto the superior VMG1312-B10A.
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Earlier in this thread, I referred to my hardware lightning warning unit as a "skyscanner" - that is incorrect, it is in fact a "Skyscan" model "Skyscan P5-3" (https://www.weathershop.co.uk/shop/skyscan-skyscan-simple).