Farm scale network links: advice

[This post was originally made to uk.comp.os.linux and uk.comp.home-networking, as I had not had a pointer to the existence of this group; please excuse multi-posting]

Right, I (with some fellow conspirators) am buying a farm.

The farm in question is on a ridge, with most of it on the east side of the ridge, where the buildings are, and part on the west side. The buildings are more or less in the centre, with the land extending about

250-300 metres in every direction.

I'm thinking that an omnidirectional wifi aerial on the top of the buildings should cover most of the east side of the ridge, but I don't know how much power I need to get 300 metres effective range on an omnidirectional. To get to a useful place to put a mast on the west side of the ridge, I'm going to need either to run 200 metres of some kind of cable, or to have a repeater station on the top of the ridge that I would need to run power to (or possibly have solar panel and/or small wind turbine).

Sticking an omnidirectional aerial on the top of the ridge is not likely to work since the ridge is too steep, and the signal would be above the level of the rest of the farm. Also, wind speeds over the ridge can be very high indeed. It might be possible to put two slightly tilted omni aerials on top of the ridge, one to 'light' the east side, one to 'light' the west, but finding a place where that would work effectively would be tricky given the land shapes.

I could run either cat 5 or fibre optic cable along the existing fence line; I know this doesn't give much protection from mechanical damage but it would work in the short term. Going along the fence lines means I'm going to need to go about 250 metres, possibly as much as 300. Cat 5 probably isn't going to go the distance - the longest distance I can find for a reliable 10base100 link on cat 5 is

177 yards, so I probably have to go for fibre, which is something I've never installed before.

So - what sort of fibre do I buy, and where do I get it? What sort of tools do I need to terminate it? I see I can get reasonably priced media converters off ebay (e.g.

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) but will these do what I need? How much power do I put into the omni aerial to get 300 metres range, and where do I get that aerial (and, if needed, amplifier)? Are there other, better, solutions I haven't thought of?

I'm in the UK, if that makes a difference to your answer.

Reply to
Simon Brooke
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I have recently read very bad reports using normal cat5 outdoors (badly affected by water?). And thats BEFORE worrying about lightening and ground potential differences. A place I worked had hundreds of cat5 cables replaced after a vending machine leaked on to them. It was cleared up in a few hours but "the people who know" said they all had to be replaced even though they seemed to work OK. It was likely an insured loss.

I can perhaps help a wee bit with the FO.

There are three kinds of fibre and they all look the same. you need to read the numbers on the side to distinguish them. The colour means NOTHING AT ALL.

65/125 - Multi mode 50/125 - Multi mode 8/125 - Single Mode can be 8, 8.5 or 9, amounts to the same thing.

MM is MUCH cheaper to implement buying new but I bet there is NO demand for SM kit on ebay:-) Fiber seems to be about the same in both cases.

At 100Mbps or less MM can go 2km. At Gigabit, MM is restricted further. It is complex and depends on the exact fibre characteristics but can be as low as 220m but if you choose the correct fibre can be 500m.

SM distance can be large - 100km or more but that distance does require more expensive kit.

SM can require power attenuators at short distances but I think that modern kit more or less eliminates that.

All your fiber must be the same type (65, 50, 8) for any run. Your senders and receivers must match both each other and the fibre too. MM or SM.

Beware of non-standards' transceivers unless you buy matched pairs.

Termination used to be (1995) professional only. Needed to test each fibre with complex kit (TDR). May not be like that now.

You can buy pre-terminated runs of any length. You can join with "barrel" connectors but not too many.

There are several (ok maybe many:-) different types of end connector used.

SC, FC/PC, ST, more I forget.


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100m - =A3114

Armoured unterminated

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water resistance of cable selected.

ALWAYS lay more strands than you need if putting in a multi-core cable.

ALWAYS leave a spare loop at the ends so that you can re-terminate if required.

Be aware of bend radius limitations (min).

I have never used, they just have a convenient web site for checking fibre prices.

If you go SM get some spare transceivers if they present themselves since new ones are (well were last time I looked) quite costly.

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Many thanks, that all looks most helpful!

Reply to
Simon Brooke

Your post come through blank. How about not using formatted text and/or attachments?

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300 m on the access point seems optimistic - it doesnt just have to transmit but also recieve the signal from your portable devices.

Golden rule of wireless is test it before you commit. If you want to do this then get some flexible wireless gear, temp mount it where you want it, and then roam around with laptop etc and see what coverage you get.

you can get weatherproof access points built into a patch panel antenna / case - that will give you some antenna gain, and let you "point" mulitple access points where you need signal.

Given the recent weather you want to operate at well below 0 C, and up to maybe 50 C+ unless it is in the shade in summer.

Only seen these as "enterprise" kit though

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cisco example only - plenty of other makes, but i havent done the outdoor stuff in anger for several years.

Agree with fibre if you want it to survive. You can get direct burial / armoured Cat5.....

Although if you get a local lightning strike on a farm your electronics are likely to get scrapped anyway, unless the power and earthing are good.

dont forget you want weather proof cable versions if it isnt armoured

- some pre terminated fibre is intended for indoor use.

if you can keep the UTP run distances down to 100m or so then with the right AP you will be able to use power over Ethernet to run the AP where you dont have local mains.

Going along the

A farm may well have metal or stone wall buildings - both block wireless pretty well.....

So if you have buildings scattered around you want access in, you may be better off with more, cheaper wireless boxes (or even a combination).

given the price of consumer routers to use indoors, maybe if you use some that let you set them up as access points and put in the various buildings, then link the building via fibre or power line networking?

So lots of rain :)

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Thanks, that's a particularly useful thought which I had not come up with; it makes locating more wireless access points much easier.

Reply to
Simon Brooke

why do your postings come across as "attachments" ? two files - one .ASC and one .TXT (which is the actual text)

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Wheat Chex

Reply to
za kAT

More thanks. Presumably to avoid interference I want to use (say) 5GHz for the bridge up to the ridge-top station, and 2.4GHz for the access point?

In practice I would be most likely to have something like this:

o o | o o | | Z GHz | | | buildings AP ridge west AP

There is no way the buildings access point is going to see the west AP, or vice versa, so interference between X and Z is a non-issue. X is probably just the main omni aerial - I could do a special directional for the bridge up to the ridge repeater but the distance isn't far (about 70 metres) and if I'm tilting the omni slightly anyway it should give good coverage.

So, what would your advice be for the values of X, Y and Z?

Reply to
Simon Brooke

5 GHz is going to have additional loss compared to 2.4 GHz (path, cable and insertion losses are all frequency sensitive) as well as the loss due to rain (in practice, insignificant over the distances you're talking about), but the extra loss can be offset by the extra antenna gain (IF the antennas are the same physical size).

OK. But what is the networking going to look like? What kind of traffic is involved, and how much of it? Are the hosts on the "East" side of the ridge going to be talking to systems on the "West" side? Or is the traffic over the ridge going to mainly "West" side to the world, and "East" side traffic rarely uses the link?

It depends on what the traffic might be, but I'd consider putting access points in the buildings on the East, and perhaps on a pole or something in the field on the West, and running them on the same channel - say "6" on 2.4 GHz. Then run separate links on different channels (say "1" and "13") from the access points up to the ridge.

That's from the buildings on the East? I'd also look at fiber from the buildings up to the ridge, but you really do want to analyze what traffic is going to look like.

Old guy

Reply to
Moe Trin

NOTE: Posting from (or some web-forums) dramatically reduces the chance of your post being seen. Find a real news server.

Depends what you call "normal cat5" cable. The jacket material is often a PVC or Teflon/FEP which in undamaged condition should be relatively watertight. If water does get in, it may wick in some distance from the entry point, and this screws up the characteristic impedance and can cause degradation of the signal. Once water (or other fluids) get in the cable, it's virtually impossible to get the stuff out. PVC doesn't have the physical and solar reliability of polyethylene which is more commonly used outdoors.

which is a real problem.

I suppose it depends on what it was that leaked out. Some of the stuff that is sold out of vending machines is pretty lethal - especially the so-called "soup". ;-)

This is true whether you are putting in telephone wire, video grade cable or fiber. The extra strands are dirt cheap compared to the cost of installing them (ESPECIALLY if trenching), never mind the fact that Murphy's Law virtually guarantees that 1) you'll need the extras, and

2) when you try to install the extra, you'll damage the original stuff. If trenching the stuff, or routing it where it can be physically damaged, it's often a good idea to put it in pipe/conduit (non-metallic if outdoors), and two additional points then apply - 1) larger sized pipe/conduit than needed (so you can pull in extra cables using the fish tapes/ropes that you also install at the same time) and 2) take lots of photographs that show where the stuff is being buried (including such landmarks that will allow you to find things next time you need to dig/work within a hundred meters of what you hid).


Old guy

Reply to
Moe Trin

I think in practice it will be mostly as you say west side traffic using the link. The west side stuff will be a lot of clients doing things like twittering and emailing one or two weeks a year (there's a music festival on adjoining land and we will be renting out a field as camp site, ideally with wifi), and two or three clients doing mostly pull stuff (web, mail) for the rest of the year. Yes, I know we won't really have the backhaul for the big weeks, but that's another issue.

For the most part, all clients will be talking to servers off site.

Yes, makes sense.

In my experience you never really know what traffic will look like before people start using the thing. And someone is bound to start doing multiplayer shoot-em-up games or something completely daft.

The problem with running fibre up to the ridge (and I'm not ruling it out) is that there's a lot of bare rock up there and trenching would be a major problem, but getting it high enough to not get damaged by animals would also be a problem. So one pole with a wind turbine and a couple of boxes looks like a very appealing idea. But I could run fibre along the existing fence line to where that crosses the ridge, and put a pole there.

Many thanks again for all your help!

Reply to
Simon Brooke

OK - that's relatively trivial then. A minor concern would be routing related if there was substantial traffic between East and West sides. This way, you can probably put each side on separate networks.

Of course - and the whining if things are complicated.

That's the usual "rock and a hard place" more accurately than normal. Rock makes trenching difficult, and usually requires a sand fill to reduce damage. But fiber is tender, which is why you would find it highly desirable to put the fiber in a conduit/pipe of some kind. If you're going to put the fiber above ground, the conduit/pipe becomes mandatory. I wouldn't try to run it via catenary, as fiber isn't meant to be continually flexed (as would happen in the wind).

The fiber still needs the protection - perhaps from the animals (for example cattle itching themselves on the fence), but also from the people climbing over the fence, etc., in addition to the wind.

Old guy

Reply to
Moe Trin

Moe Trin Inscribed thus:

Around 23/24 years ago I installed a 24 fiber link between two buildings

200 feet apart. It was 24 fibers in a Vaseline filled polyester inner with a tough vinyl outer sheath. It was suspended on a steel catenary anchored at both ends to welded steel brackets rawlbolted into corner brickwork of the buildings.

It cost a small fortune just to have the terminators fitted on the ends ! The whole thing was designed to allow a pair of mainframes to talk to each other and couple the networks between the two buildings.

Its still there to this day, and as far as I am aware still in use.

Reply to

shame about all those networks built on the overhead power pylons in the last 20 years then :)

Seriously though, the UK National Grid Co used a special machine to crawl along the top earth wire on the pylons and leave a helical coil of fibre behind - it was initially used for telemetry and teleprotection of the power system.

Then spare cores were used to roll out a national UK fibre backbone 15 to 20 years ago

This is now so common that a power company can buy an earth wire with embedded fibre cores off the shelf.

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Outfit was Energis, part of N.G., and the system was also used to distribute BBC TV programs round the country. Gave B.T. a big kick up the *****, they thought the BBC was a cash cow they could go on milking with higher and higher prices for programme distribution for ever :-)

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Context - context! I rather doubt that Simon has the overhead power pylons, never mind the kit and proper fiber to put up there ;-)

That's unfair to the back-hoes of the world. Those earth wires are substantially larger than the average messenger wire supplied with fiber, and ``should'' be less susceptible to flex damage. Incidentally the same technique is used here on the other side of the pond though I've read it's less common than direct burial.

I rather doubt the supplier is going to sell that in 100 meter lengths that are pre-terminated at a price the retail customer is willing to pay. I'm not in the trade, but most of the fiber links I hear of here are underground whenever practical. Some of this is due to weather conditions (at least once a year, we can have a thunderstorm somewhere in the valley with microbursts that will literally blow power poles over or snap them off at ground level, while colder climes can get pretty severe icing), and some it due to getting the poles out of sight, or out of the way of our very careful drivers. That's not the only hazard - over the past 6 years or so, the West coast had major network problems because of mud-slides and "forest fires" (more accurately, "wild-fires") breaking the coastal links (copper and fiber) between Los Angeles and San Francisco.

Old guy

Reply to
Moe Trin


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