Wireless Access

We have an AP-175P running outdoors with a pair of ANT-2X2-D805s (one 2.4GHz and the other 5GHz) mounted next to each other on a tower about 12-15m up in the air, pointing along a street in a city centre location - the aim is to give coverage to that street (I believe pointing slightly downwards).  I've attached a photo - the antennae are mounted on the black rail just to the right of the chimney next to the flag pole.

When I stand in the street with a laptop, I can see both the 2.4GHz and 5GHz radios, with a dBm reported varying between about -46 nearby to about -62 about 100m along the street for both.  However, whilst connections on 5GHz are fine and snappy, 2.4GHz is not very good - we normally have 40+ clients on the 5GHz radio all the time but only 1 or 2 most on 2.4GHz.

This could just be congestion on 2.4GHz (especially as it 's a city centre location) but there are other APs in adjacent buildings on 2.4GHz and those work fine if I stand near the windows of them.

Also, when I do a 'show ap arm neighbors ...' on the AP, I see lots of 5GHz APs about but no 2.4GHz APs.  The web dashboard is reporting usage <1%, channel free 99%, channel busy 1%, channel quality 100.

This makes me think there is something wrong about the 2.4GHz installation (either the antenna connection or the controller) as I find it hard to believe it's that bad (and, even if the performance was bad, I think I would see some adjacent APs and more clients at least associating).

I don't believe there's anything wrong with the physical installation of the AP (based on what I'm told) and the APs look OK from my check with a laptop.  Also, there is another situation in another location where I'm also not getting anything from the 2.4GHz radio, so I'm thinking it's something more general.

Is there anything obvious (perhaps software-wise) I should be doing before I hike up the tower?

Thanks in advance.

I think it is unlikely that you would not see any 2.4ghz radios, because each 5ghz access point has a 2.4ghz component which would be stronger.  I would say that probably something is wrong physically with the antenna.  I would try another antenna, if I could.

 Did you put in a antenna gain for the 2.4ghz side of the radio when you provisioned it?

The gain for both antennae is 5 and the fact that the dBm I'm getting on my client for each radio is similar suggests to me that the antenna itself is at least transmitting beacons OK.

Maybe the reception on the AP is the problem but I don't see how that could be asymmetric.

I think we'll have to pop back and fiddle about, but it's still odd it's doing it in two locations (although I've not see the other one yet).

Thanks for your help.

Looking at http://www.arubanetworks.com/pdf/products/ap-ant-D805_ss.pdf - there appears to be some slight built-in downtilt in the 805 antenna plate, as it is.

I assume that 0 degrees on the E-plane is perpendicular with the flat surface of the plate?

We're mechanically downtitling another AP-175 (which is working fine on 2.4GHz but mounted lower) about two notches on the Aruba bracket, which we think is about 16 degrees.  I'm not sure what these are, but we'll check.

Thanks to assistance from an on-site Aruba engineer, we've managed to resolve this issue.

It turns out it was cause by our use of third party lightning arresters (a colleague's choice), which didn't contain a Band Pass Filter (BPF).

Initially, in consulation with the Aruba TAC and our integrator, we tried swapping the third party arresters for some Aruba LAR-1 (with 2-6GHz BPF, suitable for both 2.4GHz and 5GHz radios).  Both the TAC and the integrator thought these would be fine and there was no need for a special 2.4GHz BPF, but this didn't resolve the issue.

With the visit of the on-site engineer, we then tried some LAR-24 (with 2.3-2.5GHz BPF, suitable just for the 2.4GHz radio) and this did the trick: everything started working fine!

The Aruba engineer visiting on-site had a spectrum analyser and saw a lot of cellular noise on 2.1GHz: this would be filtered by the LAR-24 but not the LAR-1 (and not at all with the third party ones).  I suspect the Aruba TAC / our integrator might have been unaware or have forgotten there is UMTS at 2.1GHz in Europe - hence the need for a more specific filter.

Anyway - using all the right stuff has got everything working!

Are you using the LAR-1 for the 5ghz channel and the LAR-24 for the 2.4 or both channels? When I was buying the antennas for my ap175's aruba suggestion 4 of each (for 2 aps). 

I apologize for bring up an old thread. 

We're using the LAR-1 on the 5GHz radio and LAR-24 on the 2.4GHz radio.

We tried the LAR-1 on the 2.4GHz radio, but that only filters 2GHz to 5GHZ and doesn't filter out the 3G signal on 2.1GHz (in Europe).  The LAR-24 does the right thing and filters out everything outside 2.3 to 2.5GHz so works correctly.