Last sunday Ansh and I did a number of long-distance wifi tests to try out some new 16dBi Vagi (dual-Yagi) antennas and we got pretty mixed results. The base station was located at my home at 2100 ft altitude near San Marcos pass with a CM-9 80mW-100mW radio and a 16dBi Vagi with horizontal polarization. The Vagi was pointed at "downtown" Santa Barbara approx 9-10mi away.
Driving down Hwy 154 we made a first stop to verify that everything was working. We then proceeded to the rooftop of a parking garage in downtown (by Anacapa and de La Guerra, but we couldn't get a good line of sight and some quick tests showed no connection. We then moved to another garage (by Anacapa and Cota Streets) where we indeed had line of sight to the base station between some roofs and trees, just a few degrees above horizontal. We set-up a 2nd Vagi with the same radio and got a connection before even carefully aiming the antenna. The signal to noise ratio (SNR) was 11-12dB at the base station and around 14dB at the mobile end. Presumably the base station gets a lot more noise by pointing at downtown. In any case, using the link over SSH was quite acceptable.
We then switched the radio at the mobile end to a new 400mW Ubiquiti SR2. The SNR at the base went up to 15-16dB, but the measured packet loss went up and using the link with SSH was rather unpleasant. Having read reports that some early cards have transmitter problems we're now wondering whether ours is affected...
We then tried 5dBi and 9dBi omnidirectional antennas. This was a little difficult due to the horizontal polarization of the base station. After toying around for a long time, we came up empty-handed. Either the 7-11 dB less gain are enough to make a connection completely impossible, or the omnis picked up a lot more local noise thereby reducing SNR further. In any case a rather disappointing result!
We're planning to do additional tests this coming sunday, this time setting up our "mobile" shop at La Vigia to make the whole thing a little easier. If anyone is interested in participating or just stopping by, please send me an email.
The experience so far tells me that we really need the 50' tower on the rover if we want to set-up a mobile station "anywhere" downtown. With all the buildings and trees it's difficult to get a predictable line of sight to anywhere. Also, while a little camera mounted behind the antenna might be cute for pointing the antenna we really need a good compass-based approach. Even through last sunday was relatively clear, it was impossible to make out any details in the area of the mountain station even when using a 15x-45x field scope: the haze plus the blurring due to air movement were too strong.
Thorsten - N6TVE