Q: Hi,

I just purchased an ASUS WL-138g which has an antenna that is really weak. It is suggested that I replace the rubber duck antenna with a better one.

I've been looking in ebay for good deals and found out many cheap deals for 10, 8, 6, 7 dbi. I mean really cheap.

I also noticed that the bigger the DBI, the longer the antenna gets. However, I found some branded antennas which has 7dbi but as short as my stock Asus antenna.

What is better, a 6-inch 7dbi branded (dlink, linksys) antenna or a 14-inch 10dbi generic antenna?

Thank you.

A: The DBI is the issue. The higher the number the more gain that is delivered. 3db will "double" the antenna range/power. So 10dbi is twice the gain of a 7dbi which is twice the gain of 4dbi etc.

Usually on "rubber duck" type antennas getting higher gain will use a longer antenna. However, It really doesn't take 14" to get good gain, that is just poor design which sometimes translates to "cheap". Chances are in that situation that a linksys 7dbi could give better than the "14 inch 10dbi" built by someone who doesn't really understand good design.It is difficult to tell who will work correctly. I usually know who is to build a large antenna out there.

Q: I have an asus WL-138g V2 wireless card on vista home 32bit. My wireless card only detects router when the antenna is horizontal and the strength is very crap. Will buying a new antenna make it work better? if so which antenna do you recommend?

A: A bigger antenna will probably help. The little one that comes with your card gives 2.2 to 3 dBi gain (1.7 to 2 times the unamplified signal). According to the specs I found on the web, your card has an RP-SMA connector. The first link in sources is to a larger antenna that is otherwise a "rubber ducky antenna" like yours. It has 9 dBi gain (8x). The second link is for a directional "cantenna" with 12 dBi gain (16x). An advantage to the second antenna is that it is directional. If your signal is crap due to interference, the directionality might help -- as long as the source of interference is not in line with the path to your router.
The first antenna will mount directly to your PCI card. The second will connect to your PCI card using an included three foot cable -- which, luckily, also has an RP-SMA connector. The cable gives you the ability to get the antenna out from behind your PC - an added advantage as PC cases are good at blocking wifi signals. Of course, having the antenna on your desktop may be inconvenient.

Do it yourself directions are available on the web if you'd like to try making your own cantenna.

To make a good decision, you need to know the strength of your current signal and your signal to noise ratio. The third link is to a free download of netstumbler. This software will tell you your signal strength, signal to noise ratio, and identify nearby networks that may be interfering. If the problem is an interfering network, you may be able to solve your problem just by setting your router to broadcast on a different channel. If not, knowing your current signal level and signal to noise ratio will help you determine the amount of gain you need.