Nanostations in the "field"

As noted in my previous post, I have been doing quite a lot of work with wi-fi radios. I took the Ubiquiti Nanostation 2 radios out for some in-field testing, and discovered some interesting things.

First, I set one up on my roof to try my "integrated solution, Mark I:" Nanostation 2 hooked up to a 7 Amp-hour (A-h) 12 volt battery, with a 5 Watt solar panel and a SunGard charge controller. It worked very well for about two days, and then the battery went dead. I then replaced the 5 watt solar panel with a 10 watt unit, and it went until the first storm before dying. Bottom line: 7 A-h is not enough battery.

In my testing, I have found that the Nanostation 2 pulls about .2 - .25 amps, or about 3 watts. Hence, to run all day requires about 72 watt-hours, or, at 12 volts, almost 6 A-h. If you don't get sunlight for a day, the battery is toast.

My next experiment was to replace the Nanostation with a 63 ohm resistor and try taking out the charge controller and see what effect that would have. The battery has been progressively losing voltage and not coming back up to full charge, and it's at 8 volts today. This indicates that the 10 W solar panel might not be quite powerful enough to keep up with the Nanostation. Interestingly, the resistor is rated for 5 watts, but it's mighty warm.

I found you could get a 50 A-h marine battery at Costco for about $50, and that should provide enough storage to get through a storm, but it won't fit into my scrounged-from-Halted NEMA 4 weatherproof box.

My next adventure involved some radio range testing with the Nanostations. I cajoled a friend of mine to come down to the fields in the Coyote Valley on Santa Teresa Blvd. We didn't have a lot of time, so I put simple "9 dBi" rubber-ducky antennas onto the radios, put one up on the truck, and sent Ethan out for a half-mile walk with a GPS and another radio. I watched the signal strength on my laptop from the truck, and was encouraged by the results.

I also tried replacing the 9 dBi rubber ducky on my end with a 15 dBi, 6+ foot antenna I had purchased. The signal strength diminished noticeably, which was disturbing, but we were out of time so we packed up and went home.

Then, last week, I went afield again to do some testing. I put one Nanostation on a 10' pole on a fencepost, and then drove to another point .85 miles away. What was intriguing about this experiment was the behavior of the "remote" radio. The stationary radio was set on Channel 3, using Wireless Distribution System (WDS), in AP mode, with the MAC address of the remote radio "hard-wired" (entered manually into the WDS table).

The remote radio was started in WDS-AP mode, but, despite having better than -80 dBm signal, would not "link" with the stationary radio. Reset into WDS-Station mode, it linked up perfectly and was able to transfer information back and forth at more than a Megabyte per second.

Why could it not connect in AP mode? Is it more sensitive to distance? (I found the distance parameter on the "stationary" radio was set to half a mile, but I can't imagine that could make too much difference) These are the mysteries in my life.

Incidentally, I tried the 15 dB antenna again and, again, it was outperformed by the rubber duckie. I thought it could have been the frequency (I had tested it on channel 11 the first time), but it was almost as bad on channel 3. I thought it could have been off-vertical (it has a pretty narrow beamwidth), so I moved it around vertical for a while to see if it got better. It didn't.

So I'm decidedly disenchanted by the 15 dBi antenna, and I'm still not sure about hooking up the NanoStations as a pseudo-mesh using WDS, half a mile apart.

Watch this space, as they say.