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Wireless Communication Hinderances

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asotmhg

Programmer
May 11, 2000
48
US
What kind of hinderances can you have with an outdoor wireless connection? We have an outdoor antenna on 50ft of coax low loss cable and it is hooked to a symbol 4131 Access point. We are using 802.11b. When the antenna is indoors it appears to work, but when it is mounted to the building you can't get signal unless you are 2ft or less from it. I am wondering if the metal roof, powerlines, or some other device could be causing the problem?
 
did u say a metal roof.... if that is between you and the ap it is like a firewall the signals are bouncing off...with modern day construction say lagging between plasterboard walls if the lagging is silver foil lined x2 it is like a firewall to the radio signals..take for instance windows if they have metal wire strenghening/mesh this also affects ap's, so as you have mentioned above look carefully at the building construction..2degree angle through a wall can make you signal go through 7 foot of wall before it reaches the reciever it will reduce your capacity to connect..

hope this helps

"Research is what I'm doing when I don't know what I'm doing."
 
The access point is inside a building with a metal roof, but there is a 50ft coax cable (supposedly low loss) that is run from inside the building to outside the building. It is then attached to an outdoor antenna that is mounted within a foot of the metal roof. I can get within a couple feet and the signal works, but not farther away. I have checked the access point and it is set to full power and primary antenna only. The antenna is hooked into the primary antenna connector. What could cause it to only work when you are a couple of feet away? I have installed a new cable, lightning arrestor, and antenna. It does the same thing.
 
50 feet is an awfully long run for 802.11x. I'd use a shorter cable and relocate the access point closer to the antenna, if possible. Also, is the cable specifically designed for 802.11, or is it just TV coax? TV coaxial cable is not designed to work at the higher frequencies (802.11x is 2.4 GHz; i.e. 2400MHz vs. a range of 54MHz to 890MHz for over-the-air TV).

Most of the 802.11 external cables I've seen are no longer than 25 feet.

Plus, like schtek said, the metal roof is a big factor. You could merely be reflecting your signal up into the air.


Dic mihi solum facta, domina.

 
What kind of antenna are you using? Directional, omni-directional, or semi-directional

CISSP, MCT, MCSE2K/2K3, MCSA, CEH, Security+, Network+, CTT+, A+
 
You might also check the AP device. I attempted a similar installation and encountered similar problems. Don't quote me on this but in the end, I was lead to believe that some AP device have two antennas. One is internal and used for reception whereas the external antenna connection was used for transmission.

As a test, you might put the AP on the roof with the 50' of coax cable in the circuit and see if this improves the distance, this might help prove the theory above.

Also, the typical small diameter (about 1/4") low loss coax cable isn't the most ideal to use. They make a larger coax (about 3/4" diameter) is more suited for these applications and I believe it comes with "N" connectors.

I'm sure the metal roof isn't helping. If you can find another way of mounting that will put the antenna further away from the roof, you'll probably get even better results.


mike
 
Thanks for all of the responses. I have determined what was causing the problem. I swapped out the access point with another access point identical to it and it began working. Apparently there was a problem with the power setting. Even though it was set to full power it was giving a very weak signal. Thanks again for all of the help.
 
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