Field Day 802.11 Wireless Network
The Engineering Web
Once a year amateur radio operators take to the field for portable radio operations. This wireless 802.11 2.4GHz network kept the scoring computers connected.
It took two years, but we finally managed a super reliable wireless network for our ARRL Field Day operations.
Our operation likes to keep the station operating positions seperated by hundreds of feet. In the past we typically used three or four single mode stations to alleviate the need for handling QSO dupe checking. However, the modern Field Day operation has site wide multi-station dupe checking with centralized and computerized logging to provide a competitive edge.
- LinkSys WRT54G Wireless 802.11b and 802.11g Routers (Pre revision 6) - Alternatively you can get the WRT54GL which is the Linux compatible LinkSys product that can still accept the DD-WRT firmware.
- DD-WRT Firmware for WRT54G Routers
- MFJ-1800 2.4GHz WiFi dBi Yagi Antenna for 802.11b and 802.11g wireless networks. Includes camera tripod socket.
- HyperGain HG2409U Omnidirectional 2.4GHz Wireless LAN Antenna with 8.5 dBi
- The Blue boxes are the Linksys WRT54G routers running the DD-WRT firmware.
- The routers do not need the IP address unless you wish to access router statistics via the built-in web page feature of the DD-WRT operating system.
- The laptop PC at the VHF operating position was so close to the "server room" it did not require the features, power and external antenna features provided by the Linksys WRT54G router
- The "server room" was a small two-person back-packing tent. Its small size kept folks out to allow IT guys to debug in peace ;)
Our transmitter stations were about as far apart as the rules allow so we used LinkSys WRT54G routers with the DD-WRT v23 software to "bridge" in the remote stations to one central unit which served as the site router. This made it easy to incorporate 2.4GHz antennas: omni on the router and those MFJ Yagi antennas on the bridges thanks to the external antenna connections. Laptops near enough to the omni router antenna needed no bridge and just connected via their internal wireless.
The following lessons learned from last year were carefully applied this year resulting in almost zero downtime of the network:
- Even if your router supports it, do not use DHCP addresses with anything other than wired or close in 802.11 PCs. Any little interruptions may cause DHCP assignments to expire creating a temporary outage... something the N3FJP client-server model just cannot tolerate.
- Put your server on the router 802.11 unit. This is the one that should have an omni antenna.
- Whatever you do, don't connect two directional antennas to the two diversity ports of the Linksys WRT54G and point them in different directions. If you do this on your central router you will confuse local laptops with the wildly varying signal strengths. The best thing to do is leave one of those little antennas on one antenna port and cable up the after market antenna on the other port.
- Make sure the omni is at least 10 feet high to get over the heads of folks or you will have outages.
- Use long dressable cables for the 2.4GHz signals, but make sure it is the "good" stuff as ever dB matters.
- Consider a server only tent to act as your "server room" where "IT" folks can debug in peace.
- Make a diode oring cable with a Gelcell and AC Power dongle for the Linksys routers so they stay up during generator refueling. If you don't you might have to "re-browse" to the \\server\fd\fdlog.mdb file on the server computer. (We did not do this this year so we had to re-browse to the server sometimes and stop and start the FDNet program).
- Befriend your IT guys and buy them a dinner as navigating through the amazing mess of the many different ways Windows does networking is a total pain in the rump. Of the many laptops we had there was zero consistency in how they behaved when accessing the share on the server computer.
All in all this was a terrific and efficient Field Day where we finally used the FDNet program the way it was intended to be used. Our 3A was comprised of SSB, CW and for the first time a multi-mode station that could do SSB, CW and Digital. The multi-mode proved priceless and various operators came and went adding CW or Phone skills. Previously we kept this third station as a Digital only station, but this time it pulled its weight nicely. Having global band-mode dupe checking is priceless.
The real-time QSO counts for CW, Digital and Phone ensured the competition between CW and Phone was kept lively.
We had a VHF station too and its computer connected via normal wireless to the server "room" just feet away.
A fellow came with a Satellite setup so we gave him an IP address and he was up and running on his internal wireless in no time.
The ability to bring additional copies of FDNet into the master log this easily (despite the Windows Share difficulties) was just too cool.