802.11N external antenna configuration

Unanswered Question
Sep 9th, 2010

Newbie question.

I want to deploy a WAP with an outside antenna to improve my range.  After  a few hours googling and reading,

can I ask some questions.

It seems that I will need an 1250 WAP, which requires 3 antennas to work correctly.


Trawling the Cicso antenna options,  the only 2 that seem relevant are the AIR-ANT1728, which says it is inside/outside,

and the more promising AIR-ANT2506 which is a mast mount option.  Unfortunately, they do not offer an outside mulitple

antenna mounting kit.

So if I have to fabricate something....  what sort of configuration do I use. I have checked out some of the hobbyist

web sites and there are some "spectacular" designs ;-)

Do I have to have all of the antennas in a row ?  Or it does not matter.

Is the spacing between the antennas important ? If so  .. what are the measurements ?

The antennas offered by Cisco have short "pigtails".  So if mounting outside, I will have to use a cable

extension.  How do I waterproof the join ?  One of the installation guides "helpfully" mentions some

coaxial sealant.  Just looks like some sort of "silastic" to me.

Your thoughts. ?

TIA

Peter

I have this problem too.
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Leo Laohoo Thu, 09/09/2010 - 19:55

New wall-mounted Indoor/Outdoor antennaes are the following:

Cisco Aironet 2.4-GHz MIMO 6-dBi Patch Antenna (AIR-ANT2460NP-R)
http://www.cisco.com/en/US/prod/collateral/wireless/ps7183/ps469/data_sheet_ant2460np.pdf

Cisco Aironet 5-GHz MIMO 6-dBi Patch Antenna (AIR-ANT5160NP-R)
http://www.cisco.com/en/US/prod/collateral/wireless/ps7183/ps469/data_sheet_ant5160np.pdf

What we've done is mount the AP and antennae units higher than the cable run.  That way moisture won't go UP the AP or antennae enclosures.  You can also get weather enclosures to protect either the AP or antennae (or both separately).

Please don't forget to rate useful posts.

NOTE:  When you are perusing these links, pay close attention to the horizontal and veritical azimuth.  This will tell you what the signal pattern is like.

peter.de.groot@... Thu, 09/09/2010 - 20:17

Many tx for the prompt reply.

Yes, I have seen these...

Unfortunately, I think these are directional antennas.

I was hoping to use something that gives me a circular horizontal azimuth.  Hence the ones I quoted

in the earlier post.

BTW .. how do I rate posts. ?

Leo Laohoo Thu, 09/09/2010 - 20:42

BTW .. how do I rate posts

On the left-hand side of "Average Rating: 0 (0 Votes)" there are stars.  The left-most is a 1 rating and the right-most is a 5 rating.

I was hoping to use something that gives me a circular horizontal azimuth.

Look at the following:  AIR-ANT5160V, AIR-ANT5175V, AIR-ANT5180V, AIR-ANT2450V, AIR-ANT2455V, AIR-ANT2480V

http://www.cisco.com/en/US/prod/collateral/wireless/ps7183/ps469/product_data_sheet09186a008008883b.html

andypenning Fri, 09/10/2010 - 12:51

Do I have to have all of the antennas in a row ?  Or it does not matter.

Is the spacing between the antennas important ? If so  .. what are the measurements ?


What I've read is that the antennas should be a multiple of the wavelength apart from each other, but no more than 4 multiples. 5 GHz averages a little over 2 inches and 2.4 GHz a little under 5 inches. So, 2.4 GHz antennas should be 5, 10, 15, or 20 inches apart for example.

Keep in mind on the 1250, 2 of the 3 antennas are used for transmitting and the 3rd is for rx only. The reasons for the multiple antennas depend on the client stations and include MIMO (11n) benefits, transmit beamforming and Clientlink, and tx/rx diversity.

peter.de.groot@... Mon, 09/13/2010 - 00:25

Very interesting ... tx very much.

I suspect that you have just read this in passing ... but is there any chance you would have

a link to that info ?

It was the beamforming, that made me wonder if the spacing was important.

Interestingly .. there appears to be absolutely nor reference to this on the Cisco

website...or the net in general.. despite hours of trawling.  Obviously I am not looking

hard enough :-)

Tx again

Regards

Peter

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