Polarisation
Antennas on APs generally cover a broad spread of the horizon whereas client antennas are usually directional, focusing on a particular region in order to get more signal and less noise. Another strategy employed by antennas to reduce noise is polarisation. This removes the microwaves oscillating in any other direction apart from the polarisation of the antenna. For large range antennas there are two or three types: Omni Linear Colinear which are vertically polarised and Waveguides which are horizontally polarised. There are also sector panel antennas which can be either.
When you are doing a signal survey it is important to know the polarisation of the AP you are surveying. For a general survey, you will need to try both polarisations.
Horizontally Polarised
AP: Waveguides
Survey antenna: grid wires mostly going left to right
Vertically Polarised
AP: Omni (linear colinear omni)
Survey Antenna: Grid wires mostly going up and down
Know your antenna
If you can, go to a location with a known AP in visual contact and try seeing what you can do with your antenna to get the optimal signal. This will let you know if you antenna has any quirks and also allow you to know how your stumbling software works.
Scanning for APs
When sweeping the sky, take a good 5-10 minutes to sweep slowly around the horizon. You need to wait for the AP to send out a beacon and you need to wait for your wireless card to go through the 13 channels. Too
hasty is wastely. Take note of the general directions where APs are found and then focus in on these directions once you have found which are the most promising APs.
Once you have done one polarisation, repeat with the other polaristion. On horizontal polarisation you will pick up the wave guides and on the vertical you will pick up omnis.
Fine tuning the signal
This is only really essential when installing equipment, but while the gear is out you may as well try this as well. Find the direction with the strongest signal, move in small increments until the signal falls off. Then sweep back in even smaller increments, zig zagging across the signal until there is no more improvement. Try raising and lowering on the horizon as well.
Save you results
Once you have finished your site survey, remember to always save your results. They are of interest to other people who are in the same area and to AP owners who like to know how far their signal is spreading.
This may inspire people to put up gear at your site to be a relay point.