Dual Yagi antenna question

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Jul 21st, 2009
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We currently have a point to point bridge set up between 2 of our buildings. We would like to set up a second bridge between the buildings and etherchannel them together. The problem is that we have a small line of sight and will need to mount the second antenna on each side on the same pole as the first. I cannot find any good documentation stating how far yagi antennas should be placed apart. Does anyone have this information?

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Roman Rodichev Tue, 07/21/2009 - 09:12
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you'll need to put the second link on a different channel anyway. Since there will be no interference between two links, you can mount second yagi as you wish.

would be interesting to see how etherchannel will behave in this setup. Etherchannel would only be configured on switches. I think as long as the spanning-tree is disabled on bridges (default), it should work.

I assume you are installing the second set of bridges, so you'll end up with four units total.

rcustersp Tue, 07/21/2009 - 09:16
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That is what I was thinking, but wanted to make sure. Yeah, we will be setting up an etherchannel at the switches on each end which should effectively give us a 108Mb link between buildings. We will have 4 units total.


Roman Rodichev Tue, 07/21/2009 - 09:25
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Let me know once you set it up. Effective bandwidth will be below 108Mbps, probably around 60-70Mbps total.

One thing for sure, you won't be able to manage bridges via IP, only through console. Once you enable etherchannel on switches, you won't be able to telnet or web into those bridges because of how etherchannel works.

rcustersp Tue, 07/21/2009 - 11:54
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Thanks for all the info. Now off to test creating an etherchannel.

dennischolmes Wed, 08/12/2009 - 07:29
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The statement that placing the bridges on separate channels will allow for no interference isn't true. If the bridges exist in the same spectrum ie. 2.4 then they need to have at least 3-4 feet of separation between antennae. Doing less results in a form of near transmitter interference. Basically this means that at extremely close ranges the antennae propagate so much RF that they have a severe negative impact on the ability to receive RF transmissions. 4 feet should be adequate if the distance of the bridge is less than a mile. More than a mile I would separate by 8-10 feet due to the increased power requirements on the bridges.


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