PCI WIFI performance not that good ? The dipole antenna supplied with PCI WIFI cards is generally a low gain (2 dBi) omni-directional (360 degree dipole) unit,  positioned low at the back of the PC, and subject to shielding from the metal chassis and any solid objects near by. The omni-directional antenna radiates the signal all over the place, not just in the direction it should be going - ie. towards the client. While OK at close range, signal strength drops off badly when the PC is located away from the host, such as at the furthermost point of a house, or when firing through several solid walls.  Other WiFi devices (eg. routers) with omni-directional antennas can suffer the same fate. Simply replacing the dipole antenna with another higher gain unit of the same type is unlikely to improve the situation much, and can even make things worse. The solution The antenna needs to be seriously upgraded and re-positioned - and most importantly, it needs to be made directional. The standard dipole antenna can easily be re-jigged to do this, and performance increased to about 10 dBi gain. Given that about 70% of the signal from a 360 degree omni antenna is going in the wrong direction, there is plenty of room for improvement. Just as a car headligh bulb uses a reflector to concentrate the light output and make it stronger in a single direction, a reflector on an antenna works in a similar way to direct transmissions down a single path between two wireless adapters.  In the above illustration, all of the wasted blue signal would be reflected into the red area. This also reduces the likelihood of interference from any broadcasts outside of that path.  So how's it done ? You unscrew the dipole antenna from the PCI card, re-attach it with a connecting cable, and mount it into a simply made 90 degree reflector. You may need a small male/female adapter for the antenna connector, but these are cheap and readily available from electrical component stores such as JayCar Electronics in Australia. The homemade EZY-F reflector increases gain and directional control - for minimal cost and effort. It acts as a wifi collector and director over a 40 degree horizontal beamwidth. Simply changing to a higher gain dipole antenna is unlikely to improve signal strength significantly - as the same basic directional deficiency will still exist.   Performance Provided the cable (pigtail) is kept reasonably short  (1-1.5 metres) to minimise signal loss,  there should be a noticable improvement. The poor signal received by a Belkin 54g PCI card in a PC at the rear of a large brick house went from :         - 40% at 48g (poor) with the standard antenna,         - to 74% at 54g (excellent) with the modified unit. A significant improvement. The signal had to pass through at least two red brick walls to the access point on the other side of the house - approximately 15 metres away. A standard Belkin 54G USB adapter picked up no signal at all -  typical of the performance from most basic USB adapters with an inbuilt antenna.   They really are pretty hopeless in all but ideal/close range conditions. Wireless adapter power While the antenna has the greatest effect on signal strength and quality, the transmit and receive sensitivity of the wireless adapter will also influence the overall level of performance. The Belkin PCI card and USB adapter are typical examples of an average performing wireless adapter, in line with most other brand name wireless adapters. In reality there are much more powerful adapters available, and it's interesting to note that few brand name manufacturers provide detailed performance specifications, to allow comparison against known high performance adapters.   The best performing 54G wireless adapters utilize the Realtek 8187L chipset.  This is primarily available in a USB based configuration. A typical cheap high powered USB adapter is seen below next to a USB extension cable and the white connector cable for a directional antenna.  The included 5 dBi omni-directional dipole antenna as fitted is actually quite good. 54G USB adapters advertised as "Hi Power" or "500 to 1500 Mwatt" (a gross exaggeration) generally use the 8187 chipset - and importantly include a connector for an external antenna.  The "L" version has the best performance. They generally come with a better than average removable dipole antenna as seen above. So if you want to beef up wireless performance to the maximum level, then you would be well advised to move away from your PCI card, to a USB adapter with this chipset. Not only does it perform much more strongly, but it allows different antennas to be fitted, the antenna to be positioned well away from the computer, and avoids any signal loss from having to use a long coax cable. A USB adapter can also be easily switched between computers, and used with a laptop to allow site surveys and war driving. Comparison testing I attached the modified EZY-F reflector to my 8187L adapter and Compaq Presario 2200 notebook, to do some more testing against my access point.   Here's the Netstumbler chart for the reflector antenna in the same bad location - an excellent, very strong signal - and a big jump up from the Belkin PCI card reading. How the EZY-F compares to a biquad antenna I next turned ny attention to a known very weak signal source in a house approximately 70 metres away, with direct line of sight through a standard 4 mm glass window pane . Once again using the same Presario setup, I attached an 11-12 dBi biquad antenna (150x150 mm) and compared it to the corner reflector. The Realtek network manager shows the difference. This suggests that the claimed 10 dBi gain for the corner reflector is fairly accurate. The very effective Intel wireless card and omni directional loop antenna in the notebook failed to pick up a signal in this situation. How it compares to a commercial 16 dBi beam yagi I next moved on to a cheap 16 dBi yagi antenna I had purchased from Ebay - $25 AUS delivered from China.  It's about 60 cm (2 foot) long, and quite well made.  See below.   I was keen to see how this commercial unit compared, so I tested all three directional antennas, against the same weak outdoor signal source. A few small shrubs interfered with the signal slightly, as it was a windy day. This time I used Netstumbler.  The results can be seen below. The Chinese yagi performed extremely well.  The 16 dBi rating seems to be a reasonable claim. There was nothing much between the other two antennas, the biquad being slightly better, and the graph basically confirmed the result of the previous test. Once again, a higher gain omni directional antenna (5 dBi dipole) failed to pick up a signal in this situation. This clearly demonstrates how the addition of a simple (but accurately focused) reflector can improve the performance of a standard dipole antenna to a level rivaling that of much more complex designs. Many people can't believe that such a simple device will provide this level of improvement, especially when compared to more elaborate and expensive commercial antennas. Final note Best performance was from the cheap yagi.  Having the tightest beamwidth, it requires a clean signal path to work well - so position is critical (nothing metallic in the way).  I eventually mounted it high up on top of a wardrobe in the back room using my Realtek 8187L USB adapter to connect to the network. See the signal strength meter below.  That is some sort of improvement. This clearly demonstrates how a directional antenna, in a high position, coupled with a powerful wireless adapter can have a massive effect upon overall network performance. Here's a good site for calculating 802.11 power output (factors in cable and connector loss, antenna and adapter performance). Be aware that the Realtek 8187L adapter requires full USB port power to operate at it's maximum rated speed. "Active" USB extension cables are a form of non powered hub, and can seriously degrade the performance of this adapter due to voltage drop - not recommended for this application. Which antenna ? The corner reflector is by far the cheapest option (virtually no cost), and very compact. Biquad antennas can also be built at virtually no cost, with very little skill required. Plans for the excellent biquad I used are available here. This site also has information on biquad construction . High gain DIY flat panel antenna kits (utilizing etched circuit board technology) can be purchased off Ebay for as little as $25 AUS delivered. Ready to go panel antennas are also available at minimal cost. There are even tiny 12 dBi patch yagi's available on Ebay for about $11 AUS delivered. I bought one recently to try out, and for indoor use it's excellent - see the back room signal strength readout below. It appears to be a direct clone of the Buffalo 5.4 dBi unit  -  costing three times as much. I suspect that the stated gain figure is grossly exaggerated.  No specifications are available regarding it's beamwidth dimensions. Despite the excellent indoor performance, it failed to pick up the weak outdoor signal source used for my previous antenna comparisons. This suggest the vertical and horizontal signal dispersion may be quite large (about 60 degrees).   It should therefore be suitable for multi story buildings where the access point is on a different level. Beam width and shape have on enormous effect upon antenna capabilities and performance.  To get the best results, the antenna must suit the application.  If you do consider a commercial antenna, and size isn't an issue, the Chinese beam yagi is a red hot performer, particularly over large distances, and an absolute bargain. Do I need a directional antenna at both ends of the signal path ? Generally, improving the client end is sufficient for the average home network. Making the access point directional will improve things further, but this reduces the area of coverage available to users.   This may be undesirable if users (clients) are likely to be scattered throughout the house. However, if the access point is located close to the side of a house and transmission is only required within the house, then fitting a wide beam directional antenna can make a lot of sense. After all, why broadcast half of the antennas output all over the disctrict, when it would be much more useful directed within the house to boost your signal level ? A parabolic or 90 degree reflector can be useful in this situation. Another trick which can improve the client signal, is to locate the omni-directional antenna near the side of the computer case that faces towards the client.  The metal case will reflect signal back past the antenna towards the client - try it and see. It can improve signal strength at the client end by up to 10 %.   An example of how wifi signals are blocked by, or reflected from metal surfaces. The EZY-F reflector design This is a variation of the EZ-10 reflector, a simple but effective design by Michael Erskine.  The very light-weight and compact 90 degree corner reflector can be attached to virtually any dipole antenna on a wireless router or access point. It is made of aluminum foil and cardboard, and costs virtually nothing. The web page at http://www.freeantennas.com/projects/Ez-10/  provides all the technical information relating to this design, the benefits of using reflectors, and the original plans. My freestanding version simply moves it away from the associated hardware, to allow better antenna positioning. It uses the same focus template for the 10 dBi gain.  So what's it look like ? Quite simple and compact.  The triangle of black poly-board or wood which locates the dipole is attached by a small screw through the centre of each reflector panel from the rear. The dipole is a press in fit through a piece of rubber hose in a hole at the focus point. No soldering, gluing, or electronics skills required. Hardware requirements All low cost items. 1 small sheet of thin flat metal (1-2 mm brass, copper, or aluminium preferred). 2 small self tapping screws. 1 small piece of 10-20 mm poly-board, wood, or hardboard to mount the dipole through. 1 short length of soft rubber hose into which the dipole will fit securely. 1 cable (low loss coax) with suitable connectors from the dipole to the PCI card. 3 base feet of some sort - or you could just hang/mount it somewhere. Construction Go to the next page - click here.