Amplifier Discussion:
The nice thing about amplifiers is that you retain the shape of your previous coverage, and just extend its range. But you quickly reach the limits of legal unlicensed transmission. Anything beyond that, and the FCC has the mission to seriously punish you. Outside the USA, there are usually even stricter regulations regarding the electromagnetic spectrum. You'll do well to know the relevant laws, as ignorance isn't a defense anywhere.
Since the actual output of the "Snow" and "Extreme" transmitters is unknown, your best bet is to use a so-called Automatic Gain Control (AGC) amplifier that puts out the rated output no matter what the input. From what I can tell, one of the best options for Airport base station amplification is to use a YDI Max-Ranger antenna that you can buy from Fab-Corp. This is a small $150 integrated amplifier (23dbm) and antenna with a MC-Card connector. Thus, it is very easy to hook up and should be foolproof.
If you need to go with stronger amplification or want to attach directional antennas to an amplifier for long-distance point-to-point connections, I recommend you take a closer look at the 500 milliWatt AGC amplifiers at Fab-Corp. Going with a 1Watt amplifier and a high-gain antenna is pointless unless you're planning to get a license from the FCC to operate a licensed transmitter - you'd be well above the legal limit. Never mind the danger of exposing yourself to that much microwave radiation.
Another option is to simply buy a more powerful base station. There are base stations out there from other vendors that feature more powerful transmitters and/or more sensitive receivers. Furthermore, they may be cheaper than the Apple product and are worth the consideration if you don't mind the extra effort setting them up and don't own a Airport base station yet. Otherwise, the Max-Ranger may be the ticket.
| Sample Mfgrs. & Models | Transmitter Power | Receiver Sensitivity at | Max. Allowable External Antenna Gain in Multi-Point Use | Admin Utility | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| (mW) | (dbm) | 54 Mbit/s | 11 Mbit/s | 5.5 Mbit/s | 2 Mbit/s | 1 Mbit/s | ||||
| 802.11b only | "Graphite" ABS | 32 | 15 | N/A | -82db | -87db | -91db | -94db | 21dbi | Apple Admin |
| "Snow" ABS | 32 | 15 | N/A | Apple Admin | ||||||
| Cisco Aironet 350 | 100 | 20 | N/A | -85db | -89db | -91db | -94db | 16dbi | Web Browser | |
| Demarctech Reliawave 200mW | 200 | 23 | N/A | -91db | -93db | -95db | -96db | 16dbi | Windows Client | |
| 802.11b&g | "Extreme" ABS | 32 | 15 | Apple Admin | ||||||
| SMC SMC2804WBR | 35 | 15 | -68 | -84db | -85db | -88db | -90db | 21dbi | Web Browser | |
| Cisco Aironet 1100 | 100 | 20 | -72 | -85db | -89db | -91db | -94db | 16dbi | Web Browser | |
Reading the chart data above, it becomes clear that there are base stations out there that offer better receive and transmit capabilities than what Apple offers. However, few things will beat the ease of use that Apple and its Admin Utility offer. If you have information to add, please e-mail me. Then, there are some more excellent antenna/amplifier information resources available from these web-sites:
- I really like the pigtails I saw at this German site. Fab-Corp sells them also.
- Tim Pozar from the Bay Area Wireless User Group on FCC regulations for 2.4GHz systems
- Trevor Marshall on how antennas can increase the security of your wireless LAN system
- Green Bay Packet Radio has some excellent resources including home-built amplifier designs. Their low-cost network set-up page is an excellent resource.
- Check out Jean Tourrilhes' comprehensive LINUX support for WLAN site.