Farm scale network links: advice

Discussion in 'Home Networking' started by Simon Brooke, Jan 10, 2011.

  1. Simon Brooke

    Simon Brooke Guest

    Slightly off-topic in ucol, I know, but it's a place where all sorts of
    geeks hang out...

    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 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. 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 before8ui.

    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 (http://goo.gl/MfD3L ) 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?

    --
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    Simon Brooke, Jan 10, 2011
    #1
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  2. Simon Brooke

    Stuart Guest

    Well, I'm not entirely sure what you are intending to put on your Wi-Fi
    network but do remember it is two-way traffic. Whatever power you need to
    put into your aerial to get your 300m range, your devices will require the
    same power and aerial gain to signal back.
     
    Stuart, Jan 11, 2011
    #2
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  3. Simon Brooke

    Simon Brooke Guest

    That is, indeed, so. I'll need to think about that. Directional
    aerials will help, of course, and highly directional wifi aerials are
    allegedly easy to construct. Indeed a cluster of directional aerials at
    the centre might be better than one omni. Any views, anyone?

    --
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    Simon Brooke, Jan 11, 2011
    #3
  4. Just a thought. Have you considered Powerline technology? If you just
    want to connect the odd PC and your electricity supply allows it, that
    might be a way of connecting up the more far flung parts of your
    empire. I've found it a useful adjunct to wireless, when I have been
    unable to get a WiFi signal where I needed it.

    --
     
    Andrew Chapman, Jan 11, 2011
    #4
  5. Simon Brooke

    Chris Whelan Guest

    On Tue, 11 Jan 2011 10:30:49 +0000, Andrew Chapman wrote:

    [...]
    One caveat might be that farms often have 3-phase supplies; you can't
    network across phases.

    Chris
     
    Chris Whelan, Jan 11, 2011
    #5
  6. Which is exactly why I said if your electricity supply allows it...

    --
     
    Andrew Chapman, Jan 11, 2011
    #6
  7. Simon Brooke

    Chris Whelan Guest

    Yep; would the OP and others have know that?

    Chris
     
    Chris Whelan, Jan 11, 2011
    #7
  8. Simon Brooke

    Simon Brooke Guest

    An excellent suggestion in the general case, but doesn't work for us as
    none of the peripheral points currently have, and some will never have,
    mains power. When and where we get round to doing the cabling for mains
    power then adding data cables on the same poles wouldn't be a big deal
    anyway (and yes, we have three phase, so data over powerline is less
    easy).

    --
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    Simon Brooke, Jan 11, 2011
    #8
  9. Yes you can network over more than one phase if you have the right phase
    coupler device.

    Here is a link showing a 3-phase coupler and how it would hook up.
    http://www.dimonoff.com/produits/view/9

    I've not purchased anything from them and have no idea the current cost
    but they will allow all three phases to share the same Ethernet provided
    the rest of the transceivers are compatible.

    I have seen similar devices used at locations in the USA where the
    buildings had 2-phase wiring. Once installed the users could pass data
    from computers on one phase to the the transceiver attached to the
    router on the other phase.
     
    GlowingBlueMist, Jan 11, 2011
    #9
  10. Simon Brooke

    Chris Whelan Guest

    On Tue, 11 Jan 2011 10:27:58 -0600, GlowingBlueMist wrote:

    [...]
    That link is to a Canadian company that is still looking for distributors
    in Canada; I don't imagine they would sell into the UK, or that it would
    be legal to use there devices here.

    Solwise say on their website:

    "If you have a 3-phase supply, don't expect Powerline networking to work
    between phases."

    Most references to communication across phase lines appears to refer to
    the US. There are always going to be losses with a coupling device, and
    the low power signal allowed by the EU can't afford that. Perhaps the
    allowed power is higher in other parts of the world?

    Chris
     
    Chris Whelan, Jan 11, 2011
    #10
  11. Simon Brooke

    Moe Trin Guest

    On Tue, 11 Jan 2011, in the Usenet newsgroup uk.comp.os.linux, in article
    Often called an alligator - big mouth, little tiny ears (loud and deaf).
    The link will work when the sum of the transmitted power (measured in
    decibels above 1 milliwatt or "dBm"), cable losses (in decibels or
    "dB"), transmitting antenna gain, path loss, receiving antenna gain and
    the cable losses are such that the signal level delivered to the receiver
    is sufficiently above the noise level of the receiver. This means
    that the antenna gain at the fixed station increases the range of both
    A to B *and* B to A. The gain gives a bigger mouth AND bigger ears.
    They're your most probable solution. However, an "omni" antenna
    with the main lobe pointed somewhat down from the horizon is a lot
    more complicated.
    Not having done a site survey, that's difficult to say. HOWEVER: If
    you have multiple antennas, you are dividing the power among those
    antennas (a splitter of some kind), and encounter mutual interference
    from the various antennas, and are loosing signal level in the cables
    that connect from the splitter/combiner to those antennas and within
    the splitter/combiner itself. Cable loss at 2.48 GHz is high, and you
    want to have the transmitter/receiver close (think inches, not meters)
    to the antennas. It's USUALLY better to have a single antenna. You
    obtain gain in all _horizontal_ directions by reducing the vertical
    coverage - think of an inflated toy balloon that is spherical, and
    then press top-to-bottom on the balloon and notice that the horizontal
    diameter increases as you do so. While you might find a power amp
    you can use to increase the output of your base station, the remote
    stations also need that increase - which is rarely practical - so the
    solution boils down to a high gain antenna at the base station to
    increase the transmitted signal level and increase the effective
    receiver sensitivity. That will work, at the cost of some coins.

    I'm not in the UK, but every government everywhere places limits on
    the radiated power of radios - which is the product of the transmitter
    power times the antenna gain minus cable losses. Someone previously
    posted a link to http://www.radio.gov.uk/publication/ra_info/ra294.htm
    as well as EU requirements found at http://www.wireless.gr/ETSI-WF1D76.pdf
    Typical EIRP limits are 100 mw or +20 dBm. 300 meters of path loss at
    2.48 GHz is going to be around 89 dB, and combined that puts about
    -69 dBm into the receiving antenna assuming clear line of sight
    between transmitting and receiving antennas. That should be adequate,
    but you need to understand Fresnel zone clearance. Higher is better.

    As for connecting the base station to your network, loose the idea of
    using copper unless you can guarantee that there will be no lightning
    strikes (of/near the base station, the ground in-between, or the
    building site). Twisted pair Ethernet generally doesn't have the
    range anyway, so you're going to need fiber OR make the buildings
    another remote (radio client of the base station). If you go with
    fiber, you almost certainly need to put it in buried (plastic)
    conduit, as that stuff _is_ fragile. If you have to ask about tools
    and instructions for terminating fiber, you almost certainly will be
    better off using pre-terminated (professionally done) fiber, as it
    takes some experience to get a good termination. Avoid splices if
    possible, as that's a place for water entry and water in cable is
    not a good thing.

    Old guy
     
    Moe Trin, Jan 11, 2011
    #11
  12. Why shouldn't you use a flat pattern omni antenna for the base station
    and a highly directional antenna at each of the remote stations?
     
    Martin Gregorie, Jan 11, 2011
    #12
  13. Simon Brooke

    Baron Guest

    Simon Brooke Inscribed thus:
    I would tend to prefer a vertical colinear antenna. Properly done will
    keep the RF from disappearing into space. It will also provide
    omnidirectional coverage. As far as clustering directional antenna is
    concerned the total power input will be divided between the antenna,
    assuming they are all correctly matched. Feed arrangement losses will
    also have to be taken into account. In short there ain't a free
    lunch !
     
    Baron, Jan 11, 2011
    #13
  14. Simon Brooke

    Simon Brooke Guest

    On Tue, 11 Jan 2011 13:43:01 -0600
    Thanks :-(
    OK, thanks :)
    I had thought running access point on the top of the ridge (either
    directly as an AP or as one end of a wireless bridge) would be more or
    less impossible, but someone else has pointed out that I could use power
    over ethernet these days which means an armoured twisted pair cable
    would be all I'd need to run. It would be possible, I think.

    --
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    Simon Brooke, Jan 12, 2011
    #14
  15. Simon Brooke

    Moe Trin Guest

    On Tue, 11 Jan 2011, in the Usenet newsgroup uk.comp.os.linux, in article
    In the first article, the O/P seemed to indicate a significant
    difference in heights between the ridgetop and the rest of the area.
    Either a medium gain omni, or something with more gain but aimed
    down at that area.
    If the remote stations are "fixed", that is HIGHLY desirable. On
    the other hand, if they are portable or mobile, ``pointy'' antennas
    have to be aimed/re-aimed if they move.

    Old guy
     
    Moe Trin, Jan 12, 2011
    #15
  16. Simon Brooke

    Moe Trin Guest

    On Wed, 12 Jan 2011, in the Usenet newsgroup uk.comp.os.linux, in article
    [cluster/multiple antennas]
    I agree with Baron <> that a
    vertical colinear antenna would be preferable (more so if you know
    what you're doing, because the colinear can be phased to aim the main
    lobe somewhat below the "horizon" - not easy, though).
    I'm not aware of many armored twisted pair cables suitable for 10BaseT
    let alone higher speeds. Unless you can "try before you buy", that
    sounds like a very poor risk.

    I'd avoid having copper over a distance due to lightning problems, and
    would suggest you talk to your insurance agent as this can be a nasty
    item they don't want to cover (or make similar noises). Bringing AC
    power up the hill separately might be OK as you can use appropriate
    isolation transformers to reduce the ground differential problems. In
    your original post, you mention using solar panel and/or a small wind
    turbine (obviously charging a battery to provide 24/7 operation), and
    that would be a good solution. It's not as if you need a hundred Watts
    up there ;-)

    Old guy
     
    Moe Trin, Jan 12, 2011
    #16
  17. Simon Brooke

    Simon Brooke Guest

    On Tue, 11 Jan 2011 21:58:01 -0600
    That's more or less right. The ridge top is at 150 metres above sea
    level, while the buildings are about 130 and the lowest point about 110.

    However on the east side of the ridge the points at which we're likely
    to want to put stations all pretty much follow the 130 metre contour,
    and all have line of sight from the top of one of the buildings
    (allowing for fresnel effect). Certainly if I tilt an omni about 5
    degrees east from vertical, the 'disk' will light all the places on
    the east side we might reasonably put a station.

    The area on the west side where we're likely to want stations is
    smaller and mostly clustered in a zone at around 120 metres altitude -
    so getting the signal to there is problematic, but covering the area
    once we've got it there is not problematic - a single access point will
    do it, probably without needing even any special aerial.
    The current plans are only for fixed ones. If we get a requirement for
    mobile ones later, I'll deal with that then! However, there's a
    significant difference between 'fixed' and having mains power; at least
    several will not have mains power (because it's much too expensive to
    run the cable) and will depend on small wind turbines and batteries for
    power.

    --
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    Simon Brooke, Jan 12, 2011
    #17
  18. Simon Brooke

    Simon Brooke Guest

    On Tue, 11 Jan 2011 21:59:49 -0600
    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 <------ X GHz ------> o
    | o <------ Y GHz -----> 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?

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    Simon Brooke, Jan 12, 2011
    #18
  19. Simon Brooke

    Moe Trin Guest

    On Wed, 12 Jan 2011, in the Usenet newsgroup uk.comp.os.linux, in article
    This description, coupled with the diagram shown in Message-ID
    <[email protected]> (posted to a.i.w, in addition to
    u.c.h-n and u.c.o.l) would seem to recommend either a base station
    within the building area, or one on the ridge with a directional
    antenna only covering this side.
    and this suggests a station in the West area, with a link of some kind
    over the ridge - either a repeater there, or an access point, RATHER
    THAN trying to cover both sides from a single site.
    Having directional antennas on the fixed site increases the signal level
    which in turn _allows_ increased bandwidth/speed or link reliability.
    Fixed sites can be powered by mains power, solar, wind or even gerbils
    running in a exercise wheel attached to a generator. That has nothing
    to do with the operation of the link. The wind turbines MAY be a
    problem if the blades are metallic and are acting as an unintentional
    reflector and changing the phase of the reflections as they rotate
    (which _might_ cause signal dropouts if the reflected signal is of
    somewhat similar amplitude to the "direct" signal).

    Old guy
     
    Moe Trin, Jan 12, 2011
    #19
  20. Simon Brooke

    Moe Trin Guest

    On Wed, 12 Jan 2011, in the Usenet newsgroup uk.comp.os.linux, in article
    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
     
    Moe Trin, Jan 12, 2011
    #20
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