Manual alignment of two WiFi (Wi-Fi), WiMAX antennas

Aligning two antennas so that they perfectly face each other is not an easy task, and can be very time consuming, and even exhausting specially when the distance between them is long. Knowing if there is line of sight between them can be complicated too. Key elements of the link like throughput and latency will be directly related to the quality of the antenna orientation. All the procedure can be done automatically using WiPlan software for the iPhone or can be done manually. In case you want to give manual installation a try we will also do out best to help you.

Most of the initial work can be done by a single person that will have to travel to both spots, but for fine tuning two people communicated through cell phones or two way radios, one at each end of the link will be necessary. Also a telescope or powerful binoculars (depends on distance of the link), a clinometer to measure inclination, and a GPS will be needed. If a GPS is not available the procedure can be made with a compass but we must take in consideration that the magnetic pole doesn't exactly coincide with the geographic pole (we can correct the values manually using published tables) and that in case we use a compass the number of calculations needed is much higher because we will need to calculate manually both positions and then check on a map the altitude that corresponds to those positions. I can't help insisting that in case yo use WiPlan software you will only need your iPhone and a few minutes.

In first place we will obtain the longitude and latitude of both link endpoints and calculate the Azimuth using the calculator at this site (http://iol.ie/~geniet/eng/azimuth.htm) or it can be determined by using the map grid of the two points and trigonometry "azimuth=90-ArcTan ((Point01Y-Point02Y)/(Point01X-Point02X))" remembering to compensate the difference map Norths ant true Norths (A.Thom).

Once we have the Azimuth we will need the height of both link endpoints, the value can be given directly by the GPS (about +/- 15 meters error), but in case we don't have a GPS, we can use an altimeter or we will need to use the longitude and altitude values to place both link endpoints in a map that has altitude information. Once we have the altitude values we can apply simple trigonometry to calculate the antenna elevation in degrees at each side of the link.

Calculations can also be obtained by placing both spots at Google Earth.

Now, before going to the field it is necessary to test the two radios to make sure that their configuration is correct and that you know how to measure the received signal strength. Once the link is tested at your facilities you can go to the field and install the antennas in their supporting structures.

Once we know the link configuration is OK we will download and print the following compass screen (here) and mark on it the Azimuth value of each endpoint. When we are at the sites we will locate the geographic north with our compass and align our printed sheet to the compass and turn our antenna so that it points, from the center, to the mark we made.

Now we can start adjusting the elevation (vertical angle) of our antennas. To do, we can use an clinometer, or, if we are using the measuring of the antenna mount kit  we will make sure that the pole where the antenna is fixed is perfectly vertical and we will use the tilt and swivel mast mount kit to tilt vertically our antenna to the degrees indicated by our calculations of elevation.

Once both antennas are aligned we can start to fine tune. We start both ends and once the signal is received and a basic link established we will measure the intensity. Keeping an eye on intensity we will, leaving the antenna in point A still, we will slowly rotate the antenna in point B, first in one direction, then in the other, observing the intensity of the received signal. Once it reaches a maximum, lock the horizontal position of antenna B. Repeat the procedure leaving antenna B fixed and rotating antenna A until a maximum is reached in the received signal. Now lock the horizontal position of antenna A.

Repeat the same procedure with the elevation angle. Take in consideration that while turning the antenna you might get a maximum and a immediate decrease, continue rotation because it might be a false maximum due to the coverage shape of the antenna (lobes).