Typically what you will need is whats called "Stumbling Rig", which is comprising of the following:
Laptop
A portable computer, either laptop/notebook or PDA which should be able to house a PCMCIA wireless card. Ideally it should be able to run on battery power alone for some decent amount of time. If stumbling during the daylight hours it would be beneficial to have a screen that is visible outdoors.
Software
The common "stumbling software" used is Netstumbler for laptops with Windows operating systems or the PDA version Ministumbler for PDA devices. Netstumbler cycles through all possible wireless channels, probing for networks, and reports the SSID of any access point that responds to the probe. If supported by the chipset it will also report signal level, noise level and records the data for a graphical history display. Netstumbler also supports GPS devices for recording at what location it last received a signal for each network - not so useful for a site survey but good for other types of surveys such as wardriving. For more software information visit Software to get Started.
Wireless Card
The ideal wireless card for stumbling would be a PCMCIA card with external antenna connectors. The classic example of this is the Senao 2511CD+ EXT2. Other possible wireless cards are USB wireless adapters with external antenna connectors (useful for PDAs) or a miniPCI card inside the laptop with a special "pigtail" (see below) bringing the internal antenna connection to the outside. Some compact flash wireless cards may also have antenna connectors.
The card should also be supported by Netstumbler or Ministumbler. Various cards are supported to a different degree in Netstumbler, most will allow basic detecting of networks but may not report signal level. The Senao mentioned earlier uses the classic Prism chipset which is supported 100% by Netstumbler. This list is a compatability list for cards that have been reported to work with Netstumbler.
Pigtail
A pigtail, also known as a flylead, is a small piece of flexible coaxial cable. This will connect from the wireless card to the antenna or possibly to a piece of coaxial extension cable between the pigtail and the antenna. Typically you will need a N-type connector of the correct gender (see Common Wifi Connectors) to connect to the antenna or coax extension lead on one end of the pigtail and the appropriate connector to connect to your wireless card at the other end of the pigtail, typically an MMCX, MC or RP-SMA connector. Internal miniPCI cards use the u.FL type connector. All combinations are either readily available or can be made to suit. See your card manual for details.
Coax (1-5m)
Coax on a stumbling rig is a great idea as it allows the laptop to sit on the ground or in the lap of an observer. This allows you to have another hand free for stablising yourself on the roof/ladder/mast. It also makes it less likely to damage the fragile pigtail as there is more slack cable to work with. Essentially it is just a coaxial extension lead with an N-type connector on both ends, one end plugs into the antenna, the other plugs into the pigtail. Make sure the genders are all correct however it is always wise to have a few gender changing connectors around just in case. Good cable to use in this situation is LMR200.
Polarised Small antenna
A cantenna, yagi or a 15dBi parabolic grid antenna are best for doing a site survey (aka stumbling) as they can be held relatively easily in one hand and don't have much wind drag. If you can pick up signals at a reasonable level with a small antenna like, it is certain that moving to a larger antenna in a permanent setup is feasible. If you can only pick up a few ESSID beacons here and there from the low gain antenna you can try again with a higher gain antenna and verify if the signal is usable with more gain.
Controlled Test
Its worth testing your equipment with a AP that you know is in range at a range of around 20 metres to first see what a good signal is like, then cover the AP in a damp towel, in a plastic bag of course, to show what a poor signal is like. If you know your stumbling rig is working you can do a site survey, it is very unlikely that you will pick up no signals from APs. If you can not detect any APs then chances are your stumbling rig is not working properly.
Safety Equipment and Buddy
Even for simple acts such as holding a ladder or calling for tools it is a good idea to have a buddy present. Stumbling can be dangerous. Air-Stream will not accept liability for injuries sustained while undertaking wireless site surveys or installs, but reccomends using best practise which includes identifying hazards and risk minimisation. This includes wearing a harness, stumbling during dry and daylight conditions, always having at least two firm footholds and a hand hold and safe use of electrical equipment.
Air-Stream Stumbling Kit
If you don't have access to stumbling equipment, there is ready made stumbling kit available to any Air-Stream Member with everything you need to do a site survey.
If you have all of these things arranged in advance you will have a much more succesful site survey, best of luck!
