Intersil, perhaps the dominant OEM of 802.11b chips sets like the Prism 2 and Prism 2.5, today introduced an extended range amplifier for those designs. The ISL3985, is a power amplifier with integrated detector and “sleep mode” function. It has a power output of 21dB (the equivalent of 125 mW).
Other high-power cards that use the Intersil core chips include:
- Senao 802.11b cards which include a 200nW SL-2511CD. Senao uses the Prism ref design and the full chipset.
- Zcomax 180mW cards uses a Prism 2.5 base with another power amplifier. It can fit inside a USB adapter for window-mounted antennas.
- The Tranzeo XI-750 USB client ($159), comes with an N Connector for easy connection to external antennas like the +13dB panel from Super Pass ($35).
- Demarc sells both 180 mW Zcomax cards and a 500 mW access point.
- Smart Bridges like the outdoor Airbridge have a relatively powerful (100 mW) radio made for outdoor use. They claim high sensitivity and easy set-up.
FCC type 15 regulations allow operation up to 4 watts EIRP at 2.4 GHz. This is 1 watt plus a 6 dB antenna gain. A 125 mW radio, for example, could legally use a +15db antenna before the 4 watt limit is exceeded. A 200 mW radio could use a +12 to +13 gain antenna before exceeding the legal limit. Superpass has a range of high gain flat panels for $35-$50.
Intersil’s chips are used by many different manufacturers of access points and PC cards. A unique feature of Intersil Prism card line is their support for Host Ap Mode. This is a special mode which enables a card to double as an Access Point without requiring special firmware. It can also act as a repeater via the Wireless Distribution System mode which allows access points to talk to other access points. By using Host AP Mode and software like No Cat on a cheap Linux machine, “free” community LANs can be constructed with a uniform log-on sequence and minimum maintenance.
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