Fitting An External rpSMA Connector To The Rear Of A Eeepc900

Copyright Terry Porter 2008,2009 Terrys email address

Note April 2009: I have installed Ubuntu 9.04 Beta, from the live cd. It is dual boot with Debian lenny on this EeeePC900 and it is just *perfect* for everyday tasks, such as internet connectivity, via WiFi or USB Wireless Broadband, browsing, etc. Very well done Ubuntu!

Installing Unubtu 9.04

  1. Download Ubuntu 9.04
  2. Burn to a CD
  3. Boot the Live CD on a pc and a create a live USB flash drive from the Ubuntu menu
  4. Use the USB flash drive to Install 9.04 onto your EeePC900

Get it here: http://releases.ubuntu.com/releases/9.04/ubuntu-9.04-beta-desktop-i386.iso

An Asus Eeepc900 makes a great WiFi site survey tool for the following reasons

  • Runs Linux, in my case Debian Lenny for the EeePC
  • Uses an Atheros mini pci card which has dual U.FL antenna connectors and gives reliable real time RSSI and NOISE levels with Kismet
  • Offers excellent battery life with an aftermarket 10.4Ah battery
  • Can be modded to fit an external rear antenna connector, which is essential for WiFi site surveys

rpSMA connector fitted to the left hand side

Initially I modded my new EeePC900 to take a rpSMA connector fitted to the left hand side, as seen in the picture below. This works fine but has a few usability problems.

  • Cannot fit into the Asus 'carry bag' as the rpSMA connector would rip it to bits
  • Because of its position on the left, holding the unit with ones left hand is very difficult as the connector and cable are right at the balance point where the unit needs to be grasped.
  • Makes insertion and removal of network cable and USB plug more difficult
  • Looks slightly tacky

This is the www.freenet.antennas.com U.FL to rpSMA connector cable I used

Fitting An External rpSMA Connector To The Rear of A Eeepc900

I noticed that there seemed to be a bit of room in the box section which comprises the left hand hinge mount base, seen below in the main picture, and the zoomed insert.

Sure enough, when the LCD panel and PCB are removed after unscrewing the two hinge mount screws ( an easy job) the area available seemed to offer just enough room for my purposes.

Step 1

  1. File two opposite edges of the “nut” section of the rpSMA Connector down to the threads, but don't file the threads. This is to reduce the internal headroom required by the connector.

This is the www.freenet.antennas.com U.FL to rpSMA connector cable I used

Step 2

  1. Pull the Eeepc900 apart, disconnect the SPEAKERS and FAN plug only, fold the pcb up and back onto the display, then remove the hinge screws and the display/pcb assembly and save in a safe place. I won't describe how to pull the Eeepc apart as there are many Internet demos available.
  2. Make room for the rpSMA connector
  3. Cut out enough space at the rear of the hinge mount box to fit the connector, I used a small “junior hacksaw” to do it. It's going to weaken the box strength, so only remove as much as you need.
  4. Drill a 6mm hole for the connector, I drilled a tiny pilot hole first, but be CAREFUL the 6mm drill WILL GRAB as it finally breaks thru, so be prepared, or rotate the drill chuck by hand to break thru to the other side.
  5. Use either a tapered reamer, file, or 6.3mm drill bit to provide a snug fit for the connector.
  6. Colored highlighter in picture below shows mods to the area I have made.


This is about the right position for the connector hole

Step 3

  1. Fit connector inside the hinge box
  2. My rear box clearance looks way too big, but the “nut” section of the connector has to be able to pass thru here, in order to reach the 6mm hole.

Step 3 alternate machining

  1. This is a second EeePC900 and here I used a Dremel rotary hand tool to machine the connector body clearance slot
  2. I also used the Dremel to machine the brass nut section down. This is the exact tool I have, http://www.justtools.com.au/images/300-25-m.jpg and I also have a small Dremel “drill stand” to hold it steady.
  3. The Dremel is *much* easier and does a neater job
  4. The machine slot needs to go all the way to the bottom or the connector just won't fit into the box area and hole

Fitted connector viewed from rear of case

Hinge Fitted (second EeePC900 with Dremel machining)

Step 4

  1. Refit the LCD and hinge assemblies
  2. Run the connector coax to the mini pci card as shown in the pictures below. Note cable is (conveniently) a firm fit in places, so use a screwdriver to push it in where required. NO forcing is needed.
  3. Remove the two UF.L connectors from the internal antennas to the mini pci card, and cover them with heat shrink (I have used RED heat shrink here) so they don't short anything out. If you leave one internal antenna connected, everything will work fine, but an external directional antenna will be useless for determining direction of Access Points at close range, i.e. inside buildings as the internal antennas are very sensitive. I did this at first, but then removed the internal antenna connections permanently, and use a external whip if I need to use the Eeepc for near WiFi connections.
  4. Fit everything back together gain, make sure no cables are jammed anywhere under the pcb mounts etc, and don't forget to make sure the speaker and fan plugs are outside the pcb when you clip it down etc.


Pcb fitted showing modified hinge and added connector

  1. The connector sits well below the pcb and does not interfere in any way

Typical Site Survey Usage

Kismet WiFi Survey Text Display On The Eeepc900

  1. Note the nice POWER and NOISE real time SIGNAL levels obtained by pressing “L” . These are obviously arbitrary numbers and not dBm as the indicated power is “29”, and the noise is ”-96”. However 29dBm would mean that 800mW is being received, which is impossible here.

Something in the order of -60 dBm would be the actual received level.

Nevertheless, the bargraph and numbers are still useful when looking at signal strengths and aligning antennas etc.

 
eeepc900-ext-antenna.txt · Last modified: 2009/04/09 20:39 by admintp
 
Recent changes RSS feed Creative Commons License Donate Powered by PHP Valid XHTML 1.0 Valid CSS Driven by DokuWiki