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infinet
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Network problem

Thu Aug 02, 2007 6:43 pm

Hello, i have an issue that my wireless network is very slow, i have for main ap routerboard 112 with a Ubiquiti Xtreme Range XR2 600mW
802.11b/g wustith an amplifier 1w, i have like 12 cust. but the problem is the network is working very slow but the ping is very good. please i need help with this issue.

thanks
 
cmacneill
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Re: Network problem

Thu Aug 02, 2007 11:53 pm

Try removing the amplifier, you shouldn't need it with a 600mW card. Check the specifications of your amplifier, most amplifiers are designed for an input power of 200mW or less so the Wireless card may be overloading the amplifier's input and creating distortion in the signal. If you really need 1W output then replace the Wireless card with a lower output model or reduce the TX power of the 600mW card to 200mW or less.

Just blasting out a high power signal is rarely the answer, you need to choose the correct combination of TX power and antenna gain to get the best out of your system. Sometimes less is more!!

PINGs are probably OK as these are usually small packets and the problems may only be apparent with larger data packets. Try doing a PING with the -l (lowercase L) switch and an increasing number from 50 to around 1400, you may find it's OK at lower values and then starts to fail at larger packet sizes.
 
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ivaring
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Re: Network problem

Fri Aug 03, 2007 10:09 am

Infact, what is your distance?.
I mean, with that power u add much noise if u are close.

Regards.
 
infinet
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Re: Network problem

Fri Aug 03, 2007 9:18 pm

thanks for the answer, the cust are 1km 2km, and the longest link is 6km, but the client ap has 200mw output power, the main problem is the amplifier?

thanks
 
cmacneill
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Re: Network problem

Fri Aug 03, 2007 10:06 pm

Where are you located? You need to be aware most countries have limits on the maximum EIRP (power). In Europe most countries are limited to a maximum of 20dBi (100mW) @ 2.4GHz. Assuming your AP is using an 8db Omni antenna with your amplifier, ignoring cables losses, you would be emitting 38dBi, nearly 8W. Maximum EIRP in the US and some other countries is 36dBi, but only with directional antennae, I believe the maximum for Omnis is 30dBi (1W), this means your Wireless TX power must be 22dBi or less, approx 200mW.

What is the gain of the antenna at the AP and Client ends? What length and type of coax cables are you using?

Using the Link Calculator at http://www.mikrotik.com/test_link.php, if you are using something like 19dBi gain antennae you definitely don't need the amplifier.

If the AP antenna is an Omni, say 8dBi gain, you should still be seeing signal powers of 61-66dB @ 6Km this should be more than enough power, depending on the receive sensitivity of your wireless cards it should provide a Link Margin of at least 10dB which should be more than enough to cater for most weather conditions.

If your close by Clients at 1Km and 2Km are pushing out too much power they will potentially swamp the longer distance clients. You need to understand Wireless power theory and use a link calculator as in the URL above to determine the power levels required for each client. Each client's power should be tuned to a level that is high enough to provide a stable connection, but not so high it's causing interference with other units.
 
infinet
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Re: Network problem

Sat Aug 04, 2007 3:50 am

thanks for the all the answers, you guys are very helpfully. but here another situation i have another rb112, like main ap without amplifier, using 600mw xr2 card, when i ping the unit i got ping answer from 600ms to 300ms, in the first place i change channels and the ping responds 3 to 4ms but now the problem came back. i have like 4 cust connect to that unit. what could be the problem. i need help with that.

thanks

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