Wireless Access

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Regular Contributor I
Posts: 181
Registered: ‎10-20-2010

Outdoor antenna cable length

I have a security requirement to mount an AP274 indoors and extend the antennas outdoors.  What is the max length of antenna cable recommended?  I heard 12 meters but not sure where I heard that info.  Assuming it is 12 meters can I use 3 x of the AP-CBL-1 which are 10 feet each male to female N-Type.  Do I have to have an ANT-CBL-1 male to male at all?  I created these images to help explain.  Do they look correct and if so can I add another AP-CBL-1 for more extension if needed up to the recommended max?

 

Female Antennas.jpg

 

Male Antennas.jpg

MVP
Posts: 1,302
Registered: ‎11-07-2008

Re: Outdoor antenna cable length

A couple of questions. What will be the use case for the 274 (mesh, client access, etc) and how far of a distance are you looking to accomplish?

 

It is not recommended to use multiple cables connected together, as each connector pair adds 0.5-1dB of loss. It would be best to source a single cable to meet your length requirements, which can be purchased from any reputable RF equipment provider (Anoison, Ventev/Terrawave, L-Com, etc). 

 

You would just need a 12m N-Male to N-Male connectorized antenna cable, and it really should be LMR-400 at a minimum. The cable and connectors will add about 5dB of loss, which will cut your coverage distance for clients or your mesh range in half (more or less). The 274, for the best performance, should be mounted outdoors with the antenna using the smallest antenna cables possible.

Jerrod Howard
Sr. Techical Marketing Engineer
Regular Contributor I
Posts: 181
Registered: ‎10-20-2010

Re: Outdoor antenna cable length

Thanks for the reply.  We are in the construction biz and have alot of greenfiled sites with trailers spread over the project.  We are looking at the Mesh option to interconnect the trailers where we can't get fiber.  Aruba sales tells me we can get up to 3Km with the AP274, directional antennas and good line of site.

 

We would also like to get some outdoor client access. 

 

Our security team has tied our hands a little with the requirement to keep the APs inside.  We are also not allowed to use the MSR or MST models.  AOS mdeols only.

 

If I order the cable to length and avoid multiple connections is there a max length I should use as a standard?  I understand shorter is better.  I am hoping 12 meters of cable is acceptable but on a trailer to trailer setup I am sure 4 meters would be more like what we would be using.

MVP
Posts: 1,302
Registered: ‎11-07-2008

Re: Outdoor antenna cable length

There's no max, every bit of loss drops the available Tx power out and Rx sensitivity. 5-6dB will likely either prevent 3km, or it would be pretty weak and slow. If the mesh distances are short, say under 1km, then 5-6dB of loss is likely acceptable but will still be significantly slower than any cited specs or graphs you might have seen.

 

12m of LMR cable is *alot* and is usually not recommended for optimal performance. You can deploy it, but there's not going to be much firm guidance on what we can provide as to performance, throughput, etc. You just need to know how it affects power output AND receive sensititivy. 

Jerrod Howard
Sr. Techical Marketing Engineer
New Contributor
Posts: 1
Registered: ‎03-02-2016

Re: Outdoor antenna cable length

I know this is a late reply, but perhaps it will help others. We discovered through real-world tests that this kind of extension is not very practical. There is a reason Aruba only sells 1- and 2-meter cables. Beyond that length the signal loss is so high that the network becomes very unreliable.  This may not be as much of a problem in a 2.4 GHz mesh mode between APs pointed at each other with external gain antennas. But if the clients are omni-antenna devices such as cellphones, then the problem is that their return signal is too weak to survive the return trip back through the coax. 

 

We started testing with 100' LMR-400 and LMR-195, and quickly found that even 20' LMR-400 is way too long.  The two-meter LMR-400 cables are about the limit, especially for 5GHz, which has twice the attenuation in LMR-400 as 2.4 GHz. 

 

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