Controllerless Networks

2 x IAP-274 APs, each with ANT-4x4-5314 5.15-5.9GHz 14dBi 30x30deg Dual Pol MIMO Hi Gain Dir N-Type Outdoor Antenna

Both APs set to 35db TX power.  Portal set to 149e with Antenna Gain set at 16db.  Point is set at 149+ and no antenna gain was configured.  We know from the data sheet the AP is only capable of +28 db max TX power.  By this logic the Portal (+35) + Antenna (+16) - 1 coax n-type cable (estimated at -1 db loss) should be around 43 db EIRP going out the door, and the Point should be around 35 db EIRP.  As is this connection sat at 80 mh, very high throughput, but often hit 100% utilization.  Someone changed the Point to 16 db antenna gain and although nothing else changed, utilization across the link dropped to <= 57%.

Why?

The antenna gain should be set based on the gain of the antenna (14 dBi) minus the calculated loss from whatever cabling was used (cables should have a tested loss number included on the certification document that hopefully came with the cable).  The antenna gain when using the 5314 should never be set higher than 14 dBi since you'll always have cabling loss.

Antenna gain MUST always be configured when using an external antenna.  Failing to do so will likely cause you to break your local laws.

The AP will utilize the configured antenna gain to determine what the actual radio transmit power needs to be in order to meet the desired EIRP, which can be up to whatever is showing in the DRT as the maximum for any particular channel.