Our coverage of the struggle to connect a not-spot attracted a lot of feedback, some of it very useful, though it seems not everyone bothered to read the piece before chipping in. The story concerned an on-going attempt to get broadband connectivity to a rural house, culminating in a microwave link of dubious construction and …
No comment on CLI & dial-up?
Most of what you do online is text-only, right?
Works for me about one week per month ... and I'm thinking about moving up there permanently.
There is a better solution
You can get a dish bracket that replaces one of your roof tiles and screws down to the rafters/purlins. Weather proofed by lead work any competent aerial/dish fitter should be able to source and fit it.
Probably cost you less than you've spent on bits of wood and coach bolts....
I would expect that journalists and tech writers do read as well as write. A good part of the reading generally involves visiting websites, either to collect fresh info, or to crossreference existing info. Links and lynx are possibilities there, but you'll still want to be able to fetch PDFs, spreadsheets and presentations without having to ponder whether it'd be faster to have them transcribed by monks and sent by carrier pigeon.
The dangers associated with connecting wires between different houses is not limited to having "different earths". I use quotations since the concept of a "single earth" is muddleheaded to begin with.
A major issue is that different houses may be on different phases and hence the equipment could experience much more than 230V.
Additionally, if there is a lightning strike nearby, then there can be very large localised potential differences at different points in the ground. Such voltages would appear across the cable and thereby across anything else connected to the cable. Such potential differences are the reason that, if you think you are about to be struck by lightning, you should keep your feet close together and not rest on your backside/hands; a shorter distance means a lower potential difference across your feet, and hence less current flowing through your body.
I strongly recommend consulting someone with *specialist* knowledge before connecting different houses together by cable.
The concept of "phase" and "neutral" ends in the power supplies. It does not propagate into the low-voltage bits that comprise the network functions. Only safety earth may be connected to the device case, and CAT5 cabling is *totally* isolated from that again, as the first thing inside the unit, past the jack, is a pair of signal transformers.
The dangers of lightning strike are real, though. The induced voltages are well beyond what those signal transformers are designed to withstand.
Asking a domestic sparky about such issues is a none starter, since the average domestic sparky will not have been trained in such things. S/he will only have been trained in what happens what happens on the property side of the meter. They will probably only have the vaguest idea about anything else.
Phase means nothing as all networking equipment runs off a DC transformer.
As with all external wiring investing in an appropriate surge protector is a good idea if you don't want to fry your equipment, or alternatively just unplug it in a lightning storm.
Also cat5 cabling works off differential voltage and have no earth, so unless there was a massive difference in the earth voltage you'd experience no problems.
Sparks and Electronic Engineers are taught about 3-phase
Whilst at college in the 90s I was taught about 3-phase during my electronics engineering studies, and I'm sure sparks are as well! The potential danger exists if two neighbours run extension leads out and the phase (live) manages to connect. If the fuse-board of each house is on the same Red/Blue/Yellow phase (and neutral), there will be no potential difference. If the houses are on different phases, the two extension leads will have 415 volts between the phases. Then things can get messy!
As for lightning. EMPs produced when lightning strikes can cause a lot of damage. I speak from experience of seeing a cable modem and two network cards fried when a house 70m away was hit. Several properties experienced failure of electronic items and the insurance companies tried to sting us the following year!
Kin d of right
To really be safe, you should optoisolate the network cabling but that's rather expensive, most surge protectors aren't worth a damn in the face of a lightning strike, direct or otherwise. I'd not trust the transformers on a network card or cheap router to protect me.
Wireless or, if you can scrounge up a cheap roll and suitable associated kit, fibre is the way to go, *no* chance of any earthing, phase, isolation breakdown or other problems killing anyone.
Oh, and there's no such thing as a DC transformer, they all run on AC and produce AC which is then rectified, smoothed and regulated as necessary.
The point about transformers
OK, so a transformer has an input at 240v RMS and puts out, for instance, 12v RMS. That then gets rectified and smoothed, etc. But even if the AC outputs got out of the box, and were on different phases, we're only talking about 20v or so.
This is well within the limits of the built-in isolators. Somebody ought to check, but if they're supposed to be useful protection against accidents, it makes sense that they'll protect against the mains voltages. Lightning strikes are a whole different problem.
You can still have nasty things happen if you run an extension lead over. So don't.
Why stand with your feet close together...
... when clearly you would be safer hopping about on one foot?
We're talking about CAT5 network cable between houses, not mains extension leads. The switches/line drivers at each end would be powered from their closest mains socket.
Noone is talking (except you) about running mains wiring from one house to the other.
I strongly suggest that you take a course in basic electricity, because you're talking complete and utter bollocks here.
The transformer sits between one phase and neutral for an input voltage of 240V AC (230V in mainland Europe), unless your house is terribly miswired. Multiple phases don't enter into it, and I am not terribly keen to know the detailed location of whatever orifice you plucked that 20V out of. Moreover, IF the transformer happens to get connected between two phases, it will burn out in short order.
..get a pair of cheap media-converters, run the thing over fibre, that'll greatly extend the range, so you could perhaps bypass un-co-operative neighbours. It also quite neatly isolates the two households in question, if that ever was a real concern.
Build an eye-sore
You should just build an absolutely giant eye-sore mast for the antenna. A mini Eiffel Tower of wood and metal joints, a huge SatAn dish at the top etc.
When neighbours complain, send them to the council. When the council complain, claim that it's the only way to get reliable broadband, claim that it's a human right (or something), and that if they want it gone, they should wire you up or offer a reliable alternative.
Ethernet is electrically isolated - at your end there are transformers in the TX and RX signal paths and the same at the other end. They're rated at 500V so you shouldn't get a problem even under fault conditions.
However, a nearby lightning strike (capable of several thousand volts per metre potential gradient[*]) might disturb things, but a strike that close might upset electronics even without the cable.
[*] which is why cows fare so badly, a nearby strike and they'll be electrocuted by the couple of thousand volts between their legs.
Ethernet is indeed electrically isolated when it works, but when assesing electrical safefty one should always consider what happens when a fault occurs.
I knew somebody who was electrcuted by a model railway layout. They were happy that the standard transformer was enough protection when running the layout in the garden. I pointed out that an ELCB would be a good idea, but I got back the answer that it was "only 16v and that can't hurt you". The grass on which the table stood was nice and wet and it just so happened there was a short between the primary and secondary on the transformer and maybe there always had been. The owner got a nasty shock when clearing some debris off the track. OK so it didn't do any lasting harm, as is often the case with 240v it was just a nasty jolt. Even so when he next used his model railway outside (with a new transformer) the ELCB reserved for his lawnmower was deployed.
Ethernet lightning protector
You can get inline Ethernet surge protectors for not much money - just give it a really good earth and you should be OK.
It won't stop the electronics that got hit from being damaged, but it should stop it from travelling through and damaging (setting fire to?) whatever's on the other end.
I know someone
who's phone line either got struck/near miss , either way it went through his modem router, through the ethernet and then into his pc, and totaled the lot!!
Fibre optics may be a solution?
He's still here to tell the tale, so he wasn't electrocuted. Also, it is an RCD,not an ELCB. It doesn't measure current in the "earth" wire (of which there may well be none and which wouldn't detect the scenario you describe anyway) - it detects an imbalance between line and neutral currents ("residual current"). RCDs are the norm nowadays, both as portable units and in consumer units . ELCBs are used in special circumstances (such as a property supplied by overhead cable, where there is an earth rod).
I'd be interested if you do construct a ground based mast system. I'm in a similar situation, and have a run of about 130 meters of CAT5E, to a post which contains a Motorola Canopy radio connected to a Yagi, which shoots a signal to the top of a feed silo down the road. I get about 1.5 mbps most of the time.
I need the 130 meters to get around a tall stand of trees- Otherwise, I'd need a mast of about 30 meters tall.
Reflector on the roof?
My knowledge of microwaves is limited to boxes than go "ping", but what about a chicken-wire 'rf-mirror' on the roof with the proper antenna in the garden. For example a row of foot or 18 inch square wire frames mounted on a single 2x2 running along the ridge.
Is there a technical college near by? This sounds like a good practical project for them.
line of sight issues
sounds like an idea worth investigating because it's basically the principle behind a satellite dish receiver, but you'd still have to have the detector in such a location to ensure birds/cats/etc don't decide to roost/sleep between the mirror and the detector. Also, if the signal is not too powerful when it gets to the mirror, it would have to be of very high reflectivity.
"The story concerned an on-going attempt to get broadband connectivity to a rural house, culminating in a microwave link of dubious construction and lamentable performance which appears, none the less, go be the best option available."
= "...TO be the best option available."
Don't be so sure about the shared earth. The "neutral" (don't like the term) is generally what is earthed at the substation. You do tend to find that "stake in the ground" earthing is quite common in the UK, mainly because your earth will be connected to your water pipes at some point and your water pipes will go into the ground. Check the potential difference between the earth and neutral at your property and you may find a good few volts.
That, however, is not the big issue with potential difference between properties. The substation will be three phase and not all properties will be on the same phase. The end result being that there could be a 415v potential difference (peak) between the live at two properties. This isn't generally speaking a big issue because it would require some sort of connection between the two which shouldn't happen on an ethernet connection unless the kit goes faulty. And of course an ethernet cable won't carry much current so if there is a short between the mains at the two houses the cable will blow like a fuse before much damage is done.
However this is the reason why we prefer fibre between buildings even if the run is short enough for ethernet. Where I've done this privately in the past I picked up a couple of used media converters cheap from ebay.
BTW the longest working CAT5e ethernet run I have of is 183m. Shouldn't work, but it does.
On the subject of the microwave link your text seems to suggest (if you insert an apparent missing word) that you can't see one house from the other. If that's the case you're never going to get a good signal. If it's not the case then the story needs amending. As for the mount you really would be better going for a standard TV aerial mast mount.
Oh and hereabouts at any rate a ground based mast of sufficient height would require planning permission so it would be a none starter. We lookied into it for a connection across the valley at home, but a mast tall enough to get good line of sight would have required permission. A mast strong enough to stand up to the winds we get here in the pennines would also have been pretty expensive to build. Luckilly the crappy broadband that caused the problem to the property in question was sorted out so it stopped being an issue.
Note to self...
Keep feet together in a lightening storm
Keep feet together in a lightening storm
Keep feet together in a lightening storm...
Present a smaller target!
It amazes me that in the 21st century, we still cannot teach people lightning storm safety. Every summer, some 'tard shelters under a tree, only to be blown across the playing field when the tree gets spanked.
Caught in a storm with no suitable shelter? Lie down in the open and get wet. If you're a lower target, the electron stream from the cloud cannot find you and it will clear off (at the speed of electricity) and hit something else. Near a pylon? Stand under it - it's a Faraday shield!
"Keep feet together" --?! But then, how will I be able to RUN LIKE HELL?!
In a lightning storm
if they don't know about Faraday, they'll get taught about Darwin.
Hard to tell from the photos, but if there's a convenient gable end wall why not stick the antenna in/on a scaffold pole, join poles together to achieve and bracket the whole arrangement to the wall (and bury one end in concrete in the garden)... should be able to drastically increase height.
Surely "keep feet together in a darkening storm"?
For lightning is enlightening...
I would have used fibre for runs over 95 metres. I know it's not cheap and the transceivers are silly money, but it will just work. And there's no issue of mains phase/neutral/earth loops or potential lightning damage.
The transceivers are not silly money; you can easily get (used) 10bT-10fx converters like the Allied Telesyn AT-MC13 from ebay for a tenner each. No need to get 100Mbit stuff if you're connecting to an ADSL line that only does a few Mbit on a nice day, downhill with a stiff tailwind, and there's no need to share multi-gazillibyte files between the premises.
But the length of fibre to cover the distance will dwarf the cost of the transceivers anyway.
Maybe search out your local ham radio club. There are many hams who work in the GHz bands and can maybe advise (and help?) with aerial strategy.
Always up for a challenge !!
The uk distance record by radio amateurs on the nearby 5.7Ghz band is 1244km (really) - although over that sort of distance line-of site is less important because other modes of propagation come into play.
AC's suggestion of searching out your local radio club is a good one - if they've got a contest group they may also have a portable mast to prove the route before you invest money in something that won't work... and it's the nature of radio amateurs (I know because I am one) to love a challenge - when conventional wisdom says something is impossible, they're the ones who go out and do it anyway because they won't take 'no' for an answer.
Long ethernet runs - just DON'T
See other comments about lightning strikes and the possibility of phase mismatch leading to 415VAC appearing where it shouldn't. (each house along a street is usually fed by alternate legs of the 3 phases on the street)
Fibre is fairly cheap and fo-ethernet converters cost about 100-200 quid apiece.
Another one talking about phase mismatches.
If you have mains voltage appearing at the ethernet side of one of the switches you're using for the interconnect, you've got a mighty serious problem already.
Now for the mains (with possibly different phases) to meet across the CAT5 cable, the above problem should manifest itself at both ends.
Ive setup hundreds of WiFi links to establish Internet for people that could not get it installed at their house.
Ubiquiti NanoStation 5 is the way to go. Tiny units and only 65 quid each. They will go 8 miles without issue and sustain over 40mb at that distance.
At the lower end i use a CAT5e Lightening Surge Arrester. They cost £90, so more than the wifi unit itself, but offers protection to everything inside the house should you be unlucky.
I've loved your little problem, and the steps you've taken.
the next suggestions assume you're in some literally isolated rockbox on a hill without any Nimby dicks to rage out at you for doing the following;
have you considered a home-turbine? if you're getting regular serious 70+ winds, the thing would pay for itself. There might still be tax breaks involved, if cameron hasnt shut that kind of thing down already. I suggest this because the companies that supply such things are probably familiar with your plight : a nice, domestic pylon you can put up in your yard that clears the trees. , and would probably have the 'spertise and smarts on hand to deal with lightning/earth issues.
the other idea tha occurred to me was negotiating with a cell company to toss up a pylon in your yard, which depending on their contract negotiation policies would give you access to a 3/4G data relay right in your back yard, plus monthly folding money from the lease in your back pocket.
Both of these might be ways to step around possibly large mast construction fees and give you a way to negotiate with local planning authorities should the need arise; you're either ecology boy, paragon of the community, or you're providing a serve and the network operator handles the local people-greasing.
wishing you the best of luck.
Wireless WAN is common here in Ireland and can be done quite cheaply with a bit of savvy. I used to use a PC-engines WRAP board in a waterproof enclosure with PoE and a MDDS dish (works well with a small mod) to get a 1Mb/s connection over about 13Km. Dish at the other end was substantial however as this was a community infrastructure.
There's a bunch of stuff at www.irishwan.ie including project howto's, equipment sources etc and lots of help in the forums.
It would help
to have some info in the public section, so that people can see that the info they're looking for is there, even if details are behind a login.
As it is now, I wouldn't bother creating an account even though I'm kindof interested.
"... a shock would require multiple failures, and be cut off by any modern fuse box, so overall a good deal safer than climbing around on the roof with insufficient safety equipment"
This whole project is a delightful series of slightly-less-dangerous choices. I'm expecting the next step to be a choice of TNT vs C3 for putty.
(Posting title courtesy of Harold Lloyd)
Three phase and shared earths
Yes of course any single property is on an single phase, but the next property may or may not be on the same phase. Different phases lead to a 415V potential difference.
In my street it is *very* easy to tell which houses are/aren't on the same phase. All I have to do is walk along the street and look at the four wires (three phases plus neutral) running between the "telegraph" poles. Different houses are connected to different cables, and hence to different phases. Yes. delivery people with cranes *hate* unloading here because of the possibility they might touch the cables (they do have a thin plastic insulation, but caution is very prudent!)
Good luck with the assumption that surge protectors will provide protection from lightning strikes. They might (or might not) the first time, but thereafter the protectors may well be invisibly compromised (hint: they fail open-circuit).
Ditto any signal isolation transformers.
As for the concept of "earth", reread Grease Monkey's post "Shared Earth"
Once again, Spamjunk
Explain how exactly two power supplies, putting out DC, being on different mains phases, will cause problems. Millions of offices are waiting with alarm, ready to rip out their mains wiring if your explanation makes any kind of sense.
As said before, long copper runs are a problem because of induction during thunderstorms. They are NOT, repeat NOT, a problem simply because the gear they're connecting might be on different mains phases.
long external network links between two switches
most switches under 8 ports are on adapters thats are double insulated, NO EARTH pin. so if the earths would never really be connected.
Beware of people that don't know what they don't know
There's some dangerous misapprehensions being propagated on this thread by people that have a GCSE-level theoretical understanding of domestic electricity power supplies. The real world is not so simple and not so predictable ("The difference between theory and practice is that in theory there is no difference...").
It is this level of misunderstanding/incomprehension that has caused to law to be changed to require people working on power supplies (including domestic) to be properly formally qualified. Sad, but probably necessary.
So, if you want to physically interconnect properties, get information from a *properly* qualified electrician.
"So, if you want to physically interconnect properties,"
Which is not what you're doing. Not at the level that an electrician is working on.
Would you call one when you want to run a string of LED lighting, powered off a wallbug, along the fence between you and your neighbour?
If you would, there's sufficient reason to question *your* knowledge of electricity, and hence your authority to put forth the advice you give.
And before you ask: yes, I have more than just theoretical knowledge of mains electricity. A good deal more. Powering-outdoors-events-with-several-hundred-visitors-levels of knowledge, on top of a-bit-more-than GCSE stuff.
Fiber the Way to Go....
If you are going to go to the trouble of 'putting a hose in the ground,' fill it with optical fiber!
Ask around and see if you can find anybody deploying fiber, the phone company, cable company, utilities, etc. (Search the local news?)
Most of the time, you can get 'scraps' of large spools left-overs for the price of just asking. They won't be using much of anything less than 100m or so, and you might get lucky and even find a chunk that is 200m or so. Connectors can be purchased that don't require expensive polishing kits, and again, maybe who ever is giving you the scrap might let you use the installation tools if you buy the connectors! The media converters (as mentioned earlier,) can be obtained from Ebay. Probably the connectors as well. If you are lucky enough to get direct burial cable, so much the better. (A bit messy, due to the silicone gels though.)
Perhaps an ADSL modem set ('cable extenders') may also fit the bill if you want to stick with copper.
1.6km @ 16.6mb/s over 24 gauge phone wire, although it's expensive...
Also look for 'long reach ethernet' gear on ebay or elsewhere.
If you are going to stick with microwave, look at these calculators:
Also, at 5.8 gig, reflectors are a real possibility if you, (or at the other end,) happen to have a neighbor that DOES have line of sight to the other end of your path.
Search for passive microwave repeaters.
If the reflector is close to either antenna, they can be fairly small.
I know of several people that have built 'fly swatter' type reflectors so the electronics are down on the ground, and the reflector is the only thing up in the air.
In the middle of the path, the reflectors get pretty big, (think BIG BILLBOARD,) so putting one up on the side of a building or barn may or may not work for you!
To all the nitwits
who keep on about the mains supply of the two houses possibly having different phases: consider the average computer room in the average office. Those do have power sockets on different phases if it's a halfway decent installation. And if having the switches on different mains phases would be a potential (hah) problem, the offices of 3Com, Cisco, Allied, Foundry, Netgear and all the others *) would have been razed to the ground and torched to a smouldering heap of slag long ago by hordes of agitated network admins. Why hasn't this happened?
Because between any one mains phase and the other you'll find two switches, each with a power supply with serious galvanical separation between the mains and low-voltage circuits *AND* signal transformers rated at 500V between the RJ45 jack and the actual switch innards. So that's *FOUR*, count'em, *FOUR* points that have to fail before you have a (short-lived, because of the lack of current-carrying capacity of network cables) short between two mains phases. And long before all four isolation points have failed you'll have different problems.
Not even a difference in earth potential will be a problem, even when using shielded CAT5, as you should connect the shield only at one end, and with unshielded it's a non-issue anyway
My residence is wired with a 3-phase supply. I'm sure I have switches, both with builtin power supplies and with wall-warts, on different mains phases throughout the house. This is not a problem, just like it is not a problem in an office, because of the isolation mentioned above.
Long cable runs are a problem because of induction by lightning strike. Not only outdoors; I've seen gear destroyed in an office building and warehouse, with all cabling indoors, in ducts. Long cable runs are NOT a problem because they may be between gear that's connected to different mains phases.
*) not excluding those of Extreme Networks and HP, but for different reasons more pertinent than this particular problem.
Sorry but in a given building you will have different phases, but usually from the same substation which will, therefore, have a common neutral. You are not however considering that two properties may be connected to a different substation. In this case the neutral is not shared so once you consider live, neutral and earth the potential differences between the sites is even larger. Anyhow lighning strikes in the area could create potential differences that will comfortably jump the isolating transformers. Futhermore I have found some idiots who reckon that shielded twisted pair will allow you to run longer ethernet cables - not good if the shield connects to the chassis earth at both ends. You're likely to get a good few volts difference in earth potential between sites normally, but imagine what would happen should lightning strike in the vicinity.
I can also cite cases where switches have been blown by sparkies connecting switches in the same cabinet to different phases.
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