Dual Radio Construction
From WNDW Wiki
A new USB antenna is born...
5 July 2006
Background
For some time now - we are using the Netgear routers with USB2.0 port and PCI radio. With these we experiment multiple uses of dual-channel routers. I doubt if there is any cheaper solution for dual-radio routers in the world. Moreover, the overall power consumption of the router with two radios transmitting in maximum power is less then 4w ! Ideal for long PoE feeds and for solar power applications.
We also found that the use of a USB radio - which is mounted outside the case of the router where the stock radio is, dramatically reduces interference. In typical multi-radio devices (such as WARP) we notice much interference between radios - even if used on different bands (i.e. 802.11g and 802.11a).
Needless the say, there is no loss of power on long coaxial feeds - as the radio is inside the antenna.
The router runs a modified "Kamikaze" version of OpenWRT with Kernel 2.6. We managed to compile a drivers for multiple USB radio chips into that kernel. At present we are experimenting with these chips: ZyDas 1211 (802.11g) and ZyDas 1201 (802.11b) - these are found in the most popular and low-cost USB-radios. Both give excellent results - we normally use them in AdHoc mode, but we got them working in client mode as well. The open-source driver is still a bit problematic in AP mode - so when we need an AP feature - we use the stock Atheros PCI radio of the Netgear.
This Netgear model is discontinued ! We bought all we could find on EBAY and elsewhere - most routers for as low as $35-40 !
These units are great - we even have a USB2.0 hard-drive connected to them - which makes them great for development. You should be able to compile on the unit itself- no need for cross-compilation and cross-debugging... We also use them to mount their own root FS from a remote NFS server !
The only device, which is reasonably priced and have these features (some of them at least) is the Asus WL-500g. However, it's hard to find these under $100.
Today's development
As you can see from the attached photos - I managed to implant a USB radio (ZD1211 based) inside a 12dBi antenna. It was tight, but done. Within days, we can report on the results of this new unit. I'm willing to bet the performance will be much better then when we use the same antenna with WRT54G.
Enjoy the photos.
Yahel.
Dharamsala.