« Archives on Wednesday, February 15, 2012

Putting up a Dipole Antenna

Putting up a HF dipole is not very hard; all it takes is a little planning, and knowing the length of your dipole. For this I am going to use the OCFD I built as an example, it is 42m long and covers the 80-10m bands.

Firstly you need to find a suitable place to put up your dipole, such as a park or similar. Preferably you’d want to have a heavy-duty squid pole or the like to hold the balun/feed point and coax up in the air; as it is the heaviest point and there’s no point using the ends of the dipole to pull up dead weight, as this will over time cause stretching of the copper wire and you’ll end up with bad SWR. The reason for using squid pole or similar is you can get a rod holder from any fishing store, which you can push into the ground to support the squid pole if its not too windy. Additionally, if there are power lines around you do not want to run your dipole parallel to them, as you’ll pic up more noise off of then.

Once you have selected a place that is adequate for your needs of mounting the ends of the dipole – trees are ideal for this. It is time to put it all up in the air; starting with the squid pole (or similar). Once the balun/feed point coax is up in the air you can deal with the ends of the dipole.

The easiest way I found to deal with the dipole ends is to use a tennis ball and some strong string – such as is used for sewing leather – you drill a hole through the tennis ball, then poke the string through on a bit of wire, and tie the string off around the tennis ball. 10 metres of string should be enough, as you only need it to pull your 4mm diameter rope up into the tree. The reason for using the string and the tennis ball is it minimises the chances of snags and getting it all stuck in the tree – 9 times out 10 if you do get snagged the string will snap hopefully close to the tennis ball and you’ll get both back.

Make sure you setup away from power and telephone lines.
It doesn’t matter if there is a little bit of droop in your dipole legs, just as long as where it droops it is 6 metres or more above the ground.

[How To] Nouveau Dualhead Setup

Well I thought I’d have another play with Nouveau the open source driver for nVidia GPU’s, as it been a while since played around with them. Since the last time I played with Nouveau it was very buggy and unstable and 3D support was even worse, but I very surprised that there is some 3D support via Gallium3D.

Anyways this how I setup my xorg.conf for dual head setup with nouveau under Debian testing (wheezy):

Section "Monitor"
          Identifier   "monitor0"
          Option       "PreferredMode" "1920x1080_60.00"

Section "Monitor"          
          Identifier   "monitor1"
          Option       "PreferredMode" "1440x900_60.00"
          Option       "RightOf" "monitor0"

Section "Device"
    Identifier 	       "device0"
    VendorName         "nVidia Corporation"
    BoardName          "GeForce GT 220"
    Driver  	       "nouveau"
    Option  	       "Monitor-DVI-I-1" "monitor0"
    Option  	       "Monitor-VGA-1" "monitor1"

Section "Screen"
    Identifier "screen0"
    DefaultDepth 24
      SubSection "Display"
        Depth      24
        Virtual 3360 1080
    Device "device0"

Section "ServerLayout"
    Identifier 			"layout0"
    Screen 			    "screen0"

At the moment I am very happy with Nouveau and going to keep using it till it borks it again 🙂

Also if you not want to go through the hassle of xorg.conf you could run or put this in your session startup file, example this what I used for testing with ~/.fluxbox/startup

$ xrandr --output DVI-I-1 --mode 1920x1080 --pos 0x0 && xrandr --output VGA-1 --mode 1440x900 --pos 1920x0 &

The above does the same as the above xorg.conf configuration.