Cisco Aironet 1300 series Wireless Bridge

Actually, 775084 / 69414397 = 0.0111 or well under 2%. That's not an excessive amount of errors, in my opinion.

When you say you're getting 3 mb/s throughput, is that just on your LAN and between the APs?
Or between APs and then out to the WAN (Internet?) ?

Are there any 802.11b devices connected while you're running these tests?

B/G channels should be 5 channels apart to prevent overlap. e.g. channels 1, 6 and 11 have no overlap; channels 4 and 9 have no overlap. But you have 2 APs talking to each other - you WANT them on the same channel... you might do a site survey and see if there are any rogue APs nearby using channels 1 through 8, since you're on channel 4. Actually, if you're transmitting outside you should try to stay on 9, 10 or 11.

What's the clearance zone around the line of sight?
What's the height of the antennae and the distance between them?
And it appears your power is turned up too high for the gain level you have.
Refer to http://www.cisco.com/en/US/docs/wireless/access_point/1300/12.2_15_JA/configuration/guide/o13chan.html for recommendations.

Darr247:

I change my channel to 10 and downgrade my power to 20 CCK and 10 OFDM. I have some good new, I gain 12 mb on my output on QCheck tools.

I realy don't know the clearance zome around the line of sight? How do I accomplish this?

The height of the antena is 30 feet high and the distance between them is about 1.1 km.

The towers should be at least 23 feet (7m) taller than the highest obstruction between them to get the 60% clearance in the First Fresnel Zone. 30 feet on both ends for a 1.1km distance should give you better than 75% of the 39 foot radius First Fresnel Zone for 2.4GHz B/G signals, after deducting the curvature of the earth for that distance. So unless you have buildings between the 2 towers, that should be good.

Did you determine if there were any 802.11b devices connected while you were doing the tests?  That could pull the whole LAN down to their speed while they were talking.

And was that just on your LAN and between the APs?
Or between APs and then out to the WAN (Internet?) ?

There are no building in between the two towers.

There are no 802.11b devices that connect to this APs. Client PCs connect to HP Procurve switch to Cisco 1300 wireless bridge and then goes to the other side of the building Cisco 1300 wireless bridge to HP switch to client PCs. How can I tell if there are other 802.11b trying to connect to my AP? Is there free tools that I can install and monitor?

Yes, just LAN and between APs.

When you say basic rate, are you referring to the "data rates"? and you wan me to disable from 1-18 and only enable 24, 36, 48 & 54? Please confirn.

No... don't disable them. Sorry... I was going back to 802.11b interference again. i.e. Using the 'default' radio settings, the data rates 1, 2, 5.5, 6, 11, 12, and 24 are set to Basic, and data rates 9, 18, 36, 48, and 54 are Enabled. Those data rate settings allow both 802.11b and 802.11g client devices to associate to the access point/bridge's 802.11g radio. If you change 1, 2, 5.5, and 6 to Enabled instead of Basic it will prevent rogue 11b devices from connecting. They don't need to be set to Disabled - just take them off Basic. That's probably not going to make any difference, though... unless the bridges are not secured there's probably no rogue 11b devices connecting and pulling the 11g radios down to 11b speeds.

Other tweaks to look at to improve throughput are the Distance command (optimizes the timout delay on the Root Bridge; doesn't need to be set on the the non-root), and enabling Short Slot Time.

What's timeout delay? Short Slot time had been enable.