[MLB-WIRELESS] World Wifi record

Wed Dec 28 16:39:46 EST 2011

In Lancefield in central Victoria we would get troppo ducting in summer to teh extent that Channel 9 in Launceston would overpower CH9 in Melbourne.

One year I recall watching the Auckland Cup on ch 1 NX received on ch0 Australian and that lasted hours.

cheers Peter
  ----- Original Message ----- 
  From: hannah commodore 
  To: Peter Berrett 
  Cc: <mike at viewbankrise.net.au> ; <melbwireless at wireless.org.au> 
  Sent: Wednesday, December 28, 2011 3:30 PM
  Subject: Re: [MLB-WIRELESS] World Wifi record

  Would tropo ducting be stable enough for a TCP stream to send the video? I know of that one instance where South Australian TV was ducting through to Victoria, carrying Underbelly to the chagrin of lawmakers :) But it only lasted 10 or so minutes, IIRC

  On 28/12/2011, at 14:02, "Peter Berrett" <p.berrett at optusnet.com.au> wrote:

    Thanks Mike

    I am no expert in this field but it seems to me that your calculations are predicated on a line of sight situation. I am well aware of the curvature of the earth and understand why the Venzualans and Italians have something of an advantage here with their high mountains.

    There is a thing called tropospheric ducting which, if the conditions are right, turns the atmosphere into a waveguide and allows signals to propogate over distances greater than line of site.

    http://en.wikipedia.org/wiki/Tropospheric_propagation

    http://www.dxinfocentre.com/propagation/tr-modes.htm

    To prove that this can be done here is a link to the Australian vhf/uhf records

    http://www.wia.org.au/members/records/data/

    http://www.wia.org.au/members/records/data/documents/VHF%20Records%20History%20111218.pdf

    The National 2.4 ghz record for VK4OX to ZL1AVZ is 2,317.5 km which is certainly over the horizon. Now they will most likely have been using voice or morse at 100 watts however it does illustrate that UHF signals can propogate over longer distances using tropospheric ducting.

    Here's how I envisage a world record could be set. We would enlist the support of the Elizabeth Amateur Radio Club who I am hopeful would be interested in assisting.

    At our end we would outfit GHO with an additional directional antenna (2.4m dish?) off either the North or South Network. This antenna would have the maximum gain possible and in fact to keep within the 36db limit we might even have to crank the power output of the router down a notch or two.

    The antenna would be precisely aligned and point towards Elizabeth, just above the horizon in terms of vertical alignment.

    Over at Elizabeth the Amateur Club has access to a water tower on which its repeaters etc are located. It also has a node for Air-stream. You can easily see it on Kettering road in Elizabeth. 

    http://www.earc.org.au/on-air/

    So they would configure an additional antenna pointing at us with an attached router hooked into Air stream.   

    It gets better though. Also on the water tower is a 2,403.452 mhz beacon with an ERP of 20 dbm transmitter which I think is 100mw. Put it this way. if we can hear that beacon here in Victoria chances are we can work some wifi dx to Adelaide.

    The distance between the water tower and GHO is about 692.5km, enough for the world record.

    The idea would be to use off the shelf wifi gear, unamplified. With that distance we would also break the amplified record at the same time.  

    cheers

    Peter VK3PB

      ----- Original Message ----- 
      From: mw at freenet.net.au 
      To: 'Peter Berrett' 
      Sent: Wednesday, December 28, 2011 10:18 AM
      Subject: RE: [MLB-WIRELESS] World Wifi record

      Hi Peter!

      It’s a noble project indeed, but I suspect that it will need a fair bit of advance planning before beginning any actual attempts! :-}

      Across 400km, you have two quite significant problems to overcome:

      <!--[if !supportLists]-->1.       <!--[endif]-->Fresnel zone: 

      At 200 km, the Fresnel zone of 2.4GHz signal expands to about 112m.  That means that if the earth were completely flat, you would need antenna heights 112m above the ground at each end to make the link work.

      <!--[if !supportLists]-->2.       <!--[endif]-->And here is the killer - curvature of the earth.

      When you are sitting on top of a mountain  about 3146m above sea level, and looking across the sea, the distance to the horizon is about 200km.  That means you need another mountain 400km across the sea that is also 3146m high before you can *just*draw a straight line between the two ends.  And that’s not taking refraction into effect (which tends to bend paths toward the earth surface, and thus making the required heights even higher!)

      So the first step to a world record attempt is to locate some feasible locations!  Now, considering that Australia’s highest point is Mt Kosciuszko in NSW, at 2228m above sea level, I suspect that you may not be able to find suitable locations in SA or Vic :-}

      I note that NZ has more than 10 peaks higher than the required levels, so that may be a good place to start!

      And may I also make an open offer:  I would be delighted to donate some MikroTik equipment to any serious project aimed at a world record attempt! :-)

      Good luck!

      Cheers, Mike.

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      From: melbwireless-bounces at wireless.org.au [mailto:melbwireless-bounces at wireless.org.au] On Behalf Of Peter Berrett
      Sent: Tuesday, 27 December 2011 10:30 PM
      To: melbwireless at wireless.org.au
      Subject: [MLB-WIRELESS] World Wifi record

      Hi all

      Would anyone out there be interested in attempting the world unamplified 2.4 ghz wifi record?

      The record I think is held by some Venezuelans (some Italians hold the 5.7 Ghz record).

      The strategy would be as follows

      1. Use an established MW node such as GHO North as one end of the link.

      2. Go about 400 km+ in the direction the node antenna is pointing and erect a node and directional antenna, perhaps solar powered, with a small computer and high gain antenna pointing at the MW node. Perhaps our friends at the Adelaide wireless group could set up a node in their group pointing at us?  

      3. Monitor 2.4 ghz beacons and when there is some tropospheric ducting try the link. Or better still just automate things so that when the station is heard it automatically tries to transfer a video from one end of the link to the other.

      Successful transfer of video = world record

      cheers 

      Peter VK3PB

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