I recently purchased a Dlink Wireless Airplus G Pci Card 2.4Ghz and a Yagi 14db antenna. I mounted the antenna on the roof with a relatively clear shot to my friends house . I'm also using lmr-400 cable. The card is setup correctly because I pickup my neighbor with the little stubby the card comes with. I have the antenna and cable to reach my friend. When I screwed in the new cable my reception was no better with the expensive antenna and cabling over the stub. Can anyone answer what am I skipping .
There is a lot of signal attenuation whe running long cable runs. LMR400 is the right kind of cable for 2.4GHz applications but the signal will drop significantly the longer the cable gets. You can find forumulas online to calculate the attenutation.
I have never been able to terminate LMR400 cable with connectors myself. Let me take that back, I have soldiered connectors on LMR400 and short cable runs worked fine. But I've not been sucessful with anything longer than a couple of meters. My soldiering skills are not bad. So, that's another thing to look at. If you are making the cables yourself maybe the soldiering is not good.
That cable is specd at 6.77 db loss per hundred feet. With a 14 db antenna, a 200 foot run would be the break even point with 13.45 db of loss. Personally, I have no experience working with this cable and would have to witness that kind of performance at 2.5 Ghz to believe it.
I prefer to bypass radio associated problems by using integrated antenna/radio devices that send data over the long cable run rather than RF.
Cable loss may not be the problem, supposedly cable runs under 10m are fine. You havent explained enought about your network, whats the distance to your friends place? and has he got a similar setup?
Wireless antenna setup 
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