TTC Shelbyville – Technical Blog

The Alfa 802.11 g/n wireless usb adapter is one of the strongest on the market.  This adapter fits desktops and laptops alike and retails under $40.00.  The SMC antenna is removable and a high gain antenna can be place on the palm sized adapter.

(Recommendations – Download the new driver here.)

One of our students Ben found this product which has been on the market for sometime.   Once we get this in, we will do a detailed review.

* Compatible with IEEE 802.11n, 802.11b/g/n wireless standards
* 2.4GHz frequency band, MIMO (Multiple Input Multiple Output)
* Complies with Universal Serial Bus Rev. 2.0 specifications
* High speed transfer TX data rate up to 150 Mbps
* Supports WPS by S/W
* Supports wireless data encryption with 64/128-bit WEP, WPA, WPA2, TKIP, AES
* Wide Range coverage
* Compliant with FCC Part 15.247 for US, ETS 300 328 for Europe
* Works with Windows 2000, XP 32/64, Vista 32/64, Windows 7 32/64.

Specifications:

- IEEE 802.11b/g/n standard
- USB 2.0 standard
- Up to 150Mbps for 802.11n connections
- Frequency Range: 2.412~2.483 GHz
- Receive sensitivity 11b: -92dBm, 11g: -76dBm, 11n: -73dBm@HT20, -70dBm@HT40

The Alfa USB adapter has an excellent utility to connect to your access points, analyze  data rates and also provides comprehensive information about your wireless network.

So what does a standard laptop wireless card detected?  Below is graphical diagram of inSSIDer from Metageeks (freeware) displaying a stationary scan in our classroom (Block walls).  With five access points, only three signals have a quality signal available.

Below is an example of the same laptop with the internal card disabled and the Alfa USB Adapter connected.

So is Are You Secure because you live in a rural area?

No..

These linksys routers are not seen from my home normally.  Ironically neither are secure.

So what if you get a larger antenna?  There is a balance of antenna type vs. antenna gain.  A larger antenna can be better,  if it is not too large.

Decibels in relation to power gain:

20 dB is an increase of 100X in power
10 dB is an increase of 10X in power
6 dB is an increase of 4X in power
3 dB is an increase of 2X in power
2 dB is an increase of 1.6X in power
1 dB is an increase of 1.25X in power
0 dB is no increase or decrease in power

Decibels/dB, how to understand their relationship to power loss:

1 dB loss: 80% of power remains.
2 dB loss: 63% of power remains.
3 dB loss: 50% of power remains.
6 dB loss: 25% of power remains.
9 dB loss: 12.5% of power remains.
10 dB loss: 10% of power remains.
12 dB loss: 6.25% of power remains.
20 dB loss: 1 percent of power remains.

If you add an antenna (yagi, omnidirectional) and need to add cable, make sure the total attenuation or loss is no more than about 3 db at 2.4 GHz or you could lose half of your total transmit power before it even reaches the antenna.