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NodeFOX

 Myself:

I am a student at LaTrobe Uni studying a Computer Systems Engineering degree in my final year. I've been a programmer since I was wee little tot, back in the old External linkSinclair Spectrum days when an upgrade from 16kb to 48kb rocked!

I spend most of my time doodling in Delphi, making PIC micro controllers smoke, researching this and that on the net and otherwise feeding my brain with large amounts of technical nitty gritty. I enjoy hacking stuff apart, forcing stuff to do what its told (not what its design for) and I usually build instead of buying (even though it usually cost twice as much in the long run).

The Plan:

I have broken my plan down into several stages, and hope to progress rapidly (don�t we all).

Stage 1 - Testing The Water

A WLAN card, ex-galaxy modified antenna, a Pigtail, some CoaxialCable hooked up in an attempt to connect to anyone/thing in my area. The oooh wow factor should be enough to keep me interested in stage 2.

Stage 2 - Hey, Look At Me

Using my WLAN with an (homebrew) omni directional antenna to allow anyone in the area to link up with me as share data about. Ohh look a network... This should be 24/7 until I hit Stage 3.

Stage 3 - Keeping The Dream Alive

Combing previous two stages to create something useful towards the whole Melbourne wireless scene. An omni to allow ClientNodes to connect to me, a directional connecting to another Stage3 nodes and some routing to allow my client cloud to connect to another client cloud.

This will turn my stage 1 developments into upstream links, I hope to have two upstream links connecting to different distant nodes at a similar stage of development.

I have been looking into antenna splitters which would allow one WLAN card to use two directional antennas to connect to two separate nodes. There are several issues to this however, such as the problems that occur with phasing and front-to-back ratios etc.

There is also the issue of noise, if everyone did this then the noise floor would increase due to the fact that a packet intended for an individual upstream node gets sent to both nodes anyway.

Stage 4 - On The Move

A mobile node in my car. This should be simple enough, I already have a PC system in my car that I use for MP3 playback but it uses a character LCD and a hacked keyboard as the faceplate, so running windows apps is out of the question at the moment.

I picked up a External linkUnisys CWD book style PC system from a swap meet for around $50. This beast is small and compact, runs a P133, has room for 1 HDD and 1 expansion slot (PCI/ISA) it even had 10BaseT network so I just had to part with my cash. The power supply has now died, so I need to crack out the soldering iron.

This was the basis of my Car MP3 Player, but I think some more horses might be required, and TV-output is a must, a 6" LCD, a WLAN card, CD/DVD, etc, etc is on the shopping list.

I am running two batteries in the car, the second battery is in the boot and runs my PC, AMPS etc and is isolated from my main battery when the ignition is turned off, so I never have to worry about a flat battery. A 300W Jaycar inverter runs the PC (my homebrew DC-DC power supply fried my first PC, and since then its been collecting dust. It�s probably in good working order, but it was struggling to supply the amps I needed).

I wrote some custom software to interface with WinAmp, a playlist database, the Character LCD and control everything.

The Hardware:


Video Feed:

I have got a board video camera that I�m considering sticking on top of my mast, maybe getting it to rotate (simple motor and gear job) and posting pics on a web site (probably a wireless one) - I might even make it interactive, little to the left.. no right.. whoa stop there. (Anyone know the legality of this)

I've already mounted this baby on a pole and recorded a 360 degree video of the area to help determine line of sight, but will probably move soon so it was pointless.

I am also considering sticking a camera in my car, now that would be cool. Live wireless video feeds at 100km/h.

The Dream:


Status and To Do:


Other Bits:

Anyone using amps? The D-Link card is 30mW, directional is say 20dBi (including cable/connector losses), that gives us 3W EIRP, if its legal to have 4W EIRP can we amp it up.

This is not needed for directional, but with Omni's maybe, all comments welcome.

Omni - to - Omni setup (i.e. base AP to car):
  Tx Power = 20dBm (WL200)
  Tx Antenna Gain = 8dBi  (omni)
  Tx Cable+Connector Loss = 2dB
 => Total Tx Gain = 20+8-2=26dB => 400mW EIRP (well below legal limit)


  Rx Antenna Gain = 8dBi  (omni)
  Rx Cable+Connector Loss = 2dB
 => Total Rx Gain = 8-2=6dBi


  Rx Receive Sensitivity = -84dBm
 => Total Power Margin = 26+6+84 = 116dBm


  Allowing 10dBm Fade Margin => 106dBm


  Solving: Path Loss (dB) = 10 log ( ( (4*PI*d) / lambda ) ^ 2 )


  Gives us 5223 meters or ~5km LoS


However if we can amp Tx power to 4W EIRP:
 => Total Tx Gain = 36dBm => 4W EIRP
 => Total Rx Gain = 8-2=6dBi  (unchanged)
 => Total Power Margin = 36+6+84 = 126dBm
  Allowing 10dBm Fade Margin => 116dBm
  Gives us 16516m or ~16km


Of course there are other issues that need to be considered such as:

Tit Bits:

Here are some various bits of info I have collected during my many www's on wireless do hickeys.


Useful Stuff:



Comments From Others:

TysonClugg> Why would you want to go all the way to 4W EIRP? If 600mW EIRP gets you connected, then using an amplifier would be excessive. There are lots of other things aside from power output that will affect how far you can link, such as LoS, ReceiveSensitivity and FresnelZone to name but a few.
are not needed for directional links, but omni to omni?

SirFlakey>20dB on a 30mW card is 3W isn't it ? .. a 20dB power ratio is a multiplication by 100.?
3W my mistake

Version 3 (old) modified Mon, 26 Jul 2021 12:49:28 +0000 by Gizi
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