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360° coverage from tower

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KD7MG's picture
360° coverage from tower

I've heard a lot of conjecture on the best way to put up a general purpose, 2.4 GHz Chan -2, 360° coverage node(s) on a tower. It's my feeling that 3 rockets mounted behind 3 120° sector antennas would be a good approach. Any other thoughts? Would it pose a problem if the sector antennas were mounted too close to each other? We might be able to space them out quite a bit, I was just curious about the minimum recommended spacing.

Since this tower requires commercial installers, we most likely would get one shot at putting anything up and I would like to have it as good as we can get on the first try without going too far overboard on our rather tight budget.

Mike, KD7MG
WU2S's picture
Why not the Omni antenna?
Is there some reason you are not considering using just one Rocket and the airMAX Omni antenna - either the AMO-2G10 or the AMO-2G13?
I don't think I'd ever use an

I don't think I'd ever use an OMNI for anything.  Not only do they pick up too much noise. It ruins the spectrum for everyone else...

k1ky's picture
360 Degree Coverage from Tower
We currently have 2 sites with 2.4Ghz Rockets and 120 Degree sector antennas deployed.  They are currently all on Channel -2 @ 5Mhz bandwidth.  Unfortunately, there is a lot of interference in the Nashville Downtown area that is rendering these units pretty deaf, so we haven't been able to run many tests.  They "appear" to be working and they are connecting to stations at other sites at times.  Our 5 Ghz installations work much better as there are a lot more frequencies to choose from and we can get good isolation betweenstations.  These are installed on cell tower tupe top hats, so they are separated by about 20 feet between arms.
Make sure to check rest of
Make sure to check rest of forums too.

This comes up as will likely many others on the subject:

Since I know the location you are speaking of I am asking the following.

Is there any reason an omni, as suggested previously, could not be installed at the top of the tower or are we restricted from that location?

BTW, Gerald and I have a 3 GHz link into the island working. It's in solid!  Now working on some 2.4 GHz issues. Should all be tied together this weekend.


GPS coordinates
GPS coordinates and I can simulate what might happen,
the 120's pick up a lot of
the 120's pick up a lot of noise as well. I'd go with five  90's or smaller if you want full coverage and not have any nulls. The horns work well also. Sucks that it's going to increase costs... But it's the way to go and also be a good neighbor. Those RF enclosures (separate form antenna) that you mount on the back of the antenna will help with front to back noise, but you still need a bit of separation between AP's/antennas.
KD7MG's picture
...but you still need a bit

...but you still need a bit of separation between AP's/antennas.

Yeah, our plan was to run all 3 of the 120° sectors on the save (2.4 / -2) frequency. Does anyone have experience in this as to how much separation is needed so they don't desense each other?

AE6XE's picture
KD7MG,    I'm aware of many
KD7MG,    I'm aware of many examples of 2 mesh nodes on the same tower, adjacent towers, and towers separated by 200'+     In no instance have I been able to observe where these 2 mesh nodes could be shielded from one another (full RF shielding, opposite directions, different levels on the tower) and not still receive each others signals on the same channel, or have a desense situation.    I expect that the mesh node protocols will always be coordinating who is transmitting -- CSMA, Clear Channel Assessment (CCA) and RTS/CTS.   Expect to have less data throughput at the site as only one mesh node will generally be transmitting at a time across all the mesh nodes the tower site is linked with. 

In comparison, I have multiple examples of 2 mesh nodes on 2 different channels literally 1' apart.  There's never a decense situation and both communicate 100% duty with their respective clients handling 2x or more the data capacity hopping through the tower site.


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