So Cal Free Net.org

The key to our 802.11a backhaul project was finding the Proxim 802.11a Harmony 8571 which is a rare 802.11a device because it has removable antennas. These are available at www.justdeals.com for $15, but with $12 shipping for the first and $4 for subsequent devices, they average out around $23 each for two with shipping. Still pretty reasonable for a device that was originally $600!

We took one apart and discovered it has an 'unwrapped' PCMCIA card in it with standard SMA connector pigtails. Its also potentially re-programmable as a bridge which would make this whole relay unbelievably cheap, but we lack the expertise to get that far! The non-standard PoE support was a nice bonus - as is the ability to run with the standard power supply 100 feet away.

The next piece of the puzzle was antennas. Most point to point 802.11a antennas are in the 5.8GHz range where point to point is allowed by the FCC. The proxim is at 5.3GHz as its designed for multipoint. Fortunately SuperPass has a suitable patch antenna that someworks across the entire 802.11a 5GHz range of 5.1-5.9GHz. At 18.5dbi with 12 degree H and 32 degree V beam its a great solution (so far).

We decided to use the Proxim AP unmodified at one end of the link and a Soekris board with a Proxim PCMCIA card removed from another AP at the other. The Soekris adds a lot to the expense, but does provide a lot of configuration flexibility. The MadWiFi Atheros chip drivers work fine with this chipset (at least for our needs).

There's a couple of ways to slice this as some new products are almost available. First, here are the parts that stay the same regardless:

Here's the rest of the parts that reflect how we built the prototype version:

Here's a 2nd variation that replaces the Proxim radio and AP with a miniPCI a/b/g card and uses the latest Soekris boards (available at the end of March):

And then there's the combination option that uses one cheap Proxim AP unmodified, and a Soekris board plus miniPCI radio card (thereby avoiding hacking a Proxim AP):

The cheapest possible version would cost $78 and requite no hardware hacking at all (just outdoor cases) - but it involves changing the firmware in the Proxim. Its possible in theory, but perhaps not in practice unfortunately:

Notes about pricing:

• Prices do not include shipping (except the Proxim APs) or sales tax.
• There'll be other odds and ends depending on your situation, especially mounting hardware such as u-bolts and masts.
• Lightning protection is not included above.
• Some pricing included user group discounts of 5-10%.
• We actually purchased the SMA-N-Female adapters from www.ecommwireless.com but discovered www.radiooutfitter.com has them for $2 less while writing this page.