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Wireless Networks Thread, Linking 2 Buildings.. in Technical; Plus directional antennas are illegal....
  1. #16

    Geoff's Avatar
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    Re: Linking 2 Buildings..

    Plus directional antennas are illegal.

  2. #17

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    Re: Linking 2 Buildings..

    > Can I ask why people are suggesting wireless when he stated there is
    > no line of sight?

    I thought the new 802.11n standard had a snazzy facility for dealing with signals bouncing off walls and suchlike. Quickly checking the information on Wikipedia, though, I get the impression that this is due to using a three-part antenna - replacing that with a single directional antenna is going to stop that facility from working. Bother.

    Hmm - didn't realise a private SDSL line was only £700 a year, might almost be worth looking at that for our sixth form centre...

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  3. #18

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    Re: Linking 2 Buildings..

    > Plus directional antennas are illegal.

    I thought legal restrictions on computer wireless kit were regarding the output power of your transmitting antenna? I thought you could legally use antennas up to around 14DBi - is that only for omni-directional antennas?

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  4. #19
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    Re: Linking 2 Buildings..


  5. #20
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    Re: Linking 2 Buildings..

    lol geoff you better inform durhamnet, they run hundreds of them!!!!, high gain ones tew.

    I imagine more than 14dbi.

    plus thats silly

    having a gain limit i mean.

    id rather have a larger antenna with a higher gain, like a small sat dish. then have a small antenna which is leagal that transmits at 16,000watts to get the signal accross :P

    higher gain = lower signal power = less cancer :P

  6. #21

    localzuk's Avatar
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    Re: Linking 2 Buildings..

    The gain limit can be increased if you have a license I believe? It also depends on the frequencies used.

  7. #22

    dhicks's Avatar
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    Re: Linking 2 Buildings..

    Ah - a little more Googling suggests a legal limit of 100mW power output for wireless devices.

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  8. #23
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    Re: Linking 2 Buildings..

    Quote Originally Posted by localzuk
    The gain limit can be increased if you have a license I believe? It also depends on the frequencies used.
    Bringing the thread back on topic for a moment, the previous poster was correct when he mentioned the line rental for a P2P sdsl circuit between buildings using the same exchange, I remembered a janet document that I read some time ago describing this scenario;

    http://www.ja.net/services/network-s...es-academy.doc

    From the document....

    BT Baseband Private Circuits (EPS 8/9)

    Originally marketed and used for voice traffic between sites, BT “Baseband” private circuits can also support digital traffic between two site LANs (Local Area Networks) by using DSL modem-routers at each end.
    By using SHDSL units, “upstream” and “downstream” data rates are the same, so a link driven by such units would most closely resemble a traditional PDH circuit (like MegaStream) supported by conventional routers. The limitations on using a Baseband circuit as a digital traffic pathway are that the buildings to be connected must share the same BT exchange and ideally the same MDF (Main Distribution Frame) at the exchange and also that the total circuit length must be below certain maxima. This is because digital traffic is sensitive to signal attenuation and line noise.

    Baseband circuits can either be four wire (EPS 8) or two wire (EPS 9). The four wire circuit can support speeds of up to 4.6Mbit/s while the two wire circuit can support up to 2.3Mbit/s, both dependant on distance and the quality of the copper wire circuit. Although quality of service is not guaranteed by BT and there is no contractual commitment to fix problems within a certain time limit, the cost of these circuits makes them an attractive possibility.


    So he was spot on about price and the distance limitations.

    I also remeber the BT learningstream product that provides very cost effective leased lines for education between sites, but overkill in this situation.

  9. #24

    Geoff's Avatar
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    Re: Linking 2 Buildings..

    Quote Originally Posted by dhicks
    Ah - a little more Googling suggests a legal limit of 100mW power output for wireless devices.
    Indeed. If you simply replace the omni-directional antenna in a WiFi device with a yagi or similar directional antenna without adjusting the output power of the transmitter then you will likely go over this legal limit in the particular direction you are transmitting.

    You must either adjust the output power of the device (which you can't in most low budget devices) so that it transmits at a limit of 100mW (thus making the whole reason you added a directional antenna rather moot) you will also need (expensive) radio diagnostic equipment to calibrate and test this and optionaly an (expensive) radio engineer to operate said equipment. Alternatively you can buy (an expensive) radio license.

    I expect by this point you would of found laying fibre or using a VPN via the Internet to be a cheaper option.

  10. #25
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    Re: Linking 2 Buildings..

    Can you get cable in your area? We have 20Mb connections available in Portsmouth - if the other site was more than a standard wireless AP could handle I'd have a cable or ADSL line just for VLAN...

    Cheap and I reckon up to the job for only 5 computers - if it was another full site then you'd be best off renting a cable.

  11. #26

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    Re: Linking 2 Buildings..

    I'd seriously look into the VPN solution, but not using SDSL as they are so expensive. There are many providers these days who will supply an ADSL2+ connection which has similar, if not faster upload speeds( and definately faster download).
    One provider worth a mention is Be (www.bethere.co.uk) who's Pro package costs £22/month and provides 24down / 2.5up. You'll need one or two of these depending on your existing access solution.

    Matt

  12. #27

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    Re: Linking 2 Buildings..

    You'll not be able to get ADSL2+ in Weston though, as it is currently only really available in major metropolitan areas (read London and Birmingham, plus a few others).

  13. #28


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    Re: Linking 2 Buildings..

    I have no idea how much it's costing, but I know someone who's company are considering a microwave radio link to link two buildings.

  14. #29
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    Re: Linking 2 Buildings..

    Quote Originally Posted by localzuk
    You'll not be able to get ADSL2+ in Weston though, as it is currently only really available in major metropolitan areas (read London and Birmingham, plus a few others).
    Actually Be is available on the Weston-super-Mare exchange...

    Sam Knows

  15. #30
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    Re: Linking 2 Buildings..

    *holds up a mug of cold coffee*

    LOL

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