WLAN and electromagnetic interference

WLAN adapter and miniPCI-express slot
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mumpitzstuff
Posts: 6
Joined: Mon Jun 08, 2009 8:58 pm

WLAN and electromagnetic interference

Post by mumpitzstuff »

Is there any way to disable the wlan module permanently? it seems that the wlan module of the fitpc2 kills my complete wlan network. if i bootup the fitpc2 and the gnome desktop is active my wlan connection from another pc is gone. If i shutdown the fitpc2 all is normal again.
it do not help if i deactive the wlan with a right mouseclick in the gnome desktop. i need another solution to work for every startup. somethink like blacklisting the init of the wlan hardware would be really useful!

Mylife
Posts: 66
Joined: Sun Jun 07, 2009 6:38 pm

Re: New repository for fit-PC2

Post by Mylife »

Assuming your running Ubuntu 9.04 :
(If you've got Ubuntu 8.04, it should be slightly different but the idea is the same)
  • Right click the Network Manager applet from the Gnome Panel ;
  • Click "Edit Connections" ;
  • Click the "Wireless" tab ;
  • Select your connection and click the "Edit" button ;
  • Uncheck the "Connect Automatically" box.
After a reboot, is your wlan still alive ?

mumpitzstuff
Posts: 6
Joined: Mon Jun 08, 2009 8:58 pm

Re: New repository for fit-PC2

Post by mumpitzstuff »

i blacklisted the wlan driver in /etc/modprobe.d, but it has nothing to do with my wlan problems (linksys wrt54..). it seems that the fit-pc2 generate electromagnetic radiation which kills the wlan connection to other computers, if the fit-pc2 stays directly beside the router. i have to place the fit-pc2 a few meters away from my router to keep the wlan connection to other computers alive. yesterday i took a piece of aluminium foil and tried to shield the fit-pc2 a little bit. the result was that the fit-pc2 kills itself after a few seconds with his own electromagnetic radiation (frozen screen - i never had that bevor). i will try to connect the case of the fit-pc2 to ground and hope to get a better electromagnetic compatibility. it looks all a little bit strange to me because my router do not have problems with other devices. as far as i know the fit-pc2 has a CE symbol and should fulfill EU norms for electromagnetic radiation.

irads

Re: New repository for fit-PC2

Post by irads »

fit-PC2 is tested for EMC as per CE and FCC Part 15 class B. It is unlikely to radiate significantly in the 2.4GHz range other than by the WiFi module.

Adding a foil around fit-PC2 is unlikely to have effect on radiation since the case is all metal, "killing itself with his own electromagnetic radiation" is very unlikely. A more likely cause could be a short circuit caused by the foil.

One of the major radiation sources is cables, in particular the HDMI cable, especially in high frequencies. You may try to check effect of disabling/disconnecting display on interference.

mumpitzstuff
Posts: 6
Joined: Mon Jun 08, 2009 8:58 pm

Re: WLAN and electromagnetic interference

Post by mumpitzstuff »

you are right. if i connect the hdmi cable to the monitor the wlan connection is dead. if i do not switch off the monitor but disconnect the dvi cable (i dont remove the short hdmi cable) i do not have a problem anymore. the wlan problem has really something to do with the monitor signal over the hdmi/dvi cable. thx for the tip.

irads

Re: WLAN and electromagnetic interference

Post by irads »

A high quality shielded HDMI cable might show better EM behavior.

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