I have setup a wireless network inside my friends car show room. It is a shop surrounded by glass panels and a classic car parking in the middle.

My problem is that sometime my pc show signal very good but sometime can scanning for half an hour without locating the router(which is on the other end of the room about 25 metres apart).

My friend say change the wireless adaptor to a better one, but I doubt so is the adaptor fault.

Why is it so? Is it that the signal is absorb away somehow?

How can I improve the linking? Will it help if I shift the router to a higher place like on top on a cupboard?

Any suggestion welcome and thanks very much.

give this a good read, it may help!

Going wireless is an exciting milestone. Whether you're in the process of setting up your network or you've already been working happily without wires, you're probably familiar with Public Enemy Number One in the wireless world: interference.
If you've experienced interference, you know how annoying it can be: now you have a signal; now you don't. It's like hide-and-seek.without the fun. But wait! Don't throw your hands (or your laptop) in the air. We'll tell you how to determine what might be affecting your signal, and how to get back to being your old productive self.
What is it?
Think of a time when your favorite radio or television station wouldn't come in due to bad weather. When the storm passed, the signal became clear again. Similarly, because your wireless network relies on radio waves traveling through your home, your signal may waver for a variety of reasons. How will you know if you're experiencing interference in the first place? We'll help you identify and solve potential problems.
Check your signal
Thankfully, the client software that comes with almost all wireless network adapters can help you monitor your network's performance. With most systems, there will be a signal-strength meter in the Windows system tray (usually found in the bottom right corner of your screen).
In addition, the client software itself probably has a more in-depth system for testing signal strength. This feature is commonly called a link test function, although it may be called something else (depending on the manufacturer). Check your manual or the online help system, which usually measures:
Signal strength: Measured in decibels compared to one milliwatt (or dBm), the signal strength is sometimes referred to as signal level. The higher this number is, the better chance you have for a full-speed connection between your access point and your PC.
Noise level: Ideally, you want the noise level (also measured in dBm) to be as low as possible. Cordless phones and microwaves are common culprits for increasing the noise level.
Signal-to-noise ratio (SNR): This is the most telling of the numbers because it compares the strength of the signal with the noise that is interfering. SNR is measured in decibels (dB), and a higher number is good news.
Placing your access point
The location of your access point (AP) is key. With a little planning, you can avoid potential interference and save yourself time, money, and frustration.

Here are some pointers:
Pick a place near the center of your home.
Avoid mounting your AP on the wall. The best place is six or more inches from the wall.
Keep the AP out of the line of sight of microwaves, cordless phones, refrigerators, and other appliances that contain metal.
Your computer can cause interference, so try keeping the AP separate.
Avoid putting the AP low to the ground. Instead, keep it on a table or a shelf.
If your house is large, you may need two access points.
Troubleshooting tips
If your wireless network is all set up and you're experiencing interference, here are some ideas for improving the signal:
Move the access point. See the above section for pointers, and if all else fails, walk around with the AP while someone else monitors your signal strength.
Change channels. If you've got a neighbor with a wireless network, you may be operating on the same channel. You can change the channel in the software that came with your wireless access point.
Move the antenna. Not all antennas have the same range of coverage, so finding the best position is a matter of trial-and-error. Try moving yours around and changing the angle.
Change phones. If you have an 802.11b or g network, consider one of the newer 5GHz cordless phones. If you have an 802.11a, try a 2.4GHz phone. Better yet, an older 900MHz phone won't interfere with either type of network.
Check other network obstructions. Other network obstructions include ceramic tile, concrete, and even stacks of newspapers, as well as Bluetooth-enabled devices such as laptops and PDAs.
Consider an upgrade. If you're using 802.11b, you might have better luck with the newer 802.11g devices that have more non-overlapping channels and less interference. Plus, they're almost five times as fast!

Thanks for the reply,

If I wanted to use the method of 2 access point. What should I do and any brand or model you recomend?

i personally prefer linksys, d-link is also a well recognized brand as well.

What model? Is it call bridge?

use an "access point" or for a couple of more (not much) dollars, a wireless router.
then you go into the router's setup, and enable it as a wirelesas access point.