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Better living though radiation

This cold that I have been trying to ignore all week has finally caught up to me. So, at the moment I am stapled to the couch, pinned down by a whole ton of tired.

I took advantage of a boss-free day yesterday to do some more work on Hartford_Open_WiFi. Last Friday when I installed the access point next to my office I used the stubby-little dipole antennas that came with the AP (top image). Yesterday I replaced them with a pair of larger antennas that hang from the ceiling. The new antennas come with a small bracket that clips onto the metal grid of the suspended ceiling; the antenna then threads onto the bracket. What you wind up with looks like two 18" long pieces of 1.25" diameter PVC pipe sticking down from the ceiling (bottom image). In an office environment with a high enough ceiling, you hardly notice that they're there. These antennas are omnidirectional, like the little stubby ones that come with the APs, but have 2.5 times the sensitivity (5.2dBi vs. 2.1 dBi). This translates into much longer range.

Cisco ruggedized Aironet 350 AP with 2.1 dBi omnidirectional antennas

Cisco 5.2 dBi ceiling-mount omnidirectional antenna


After doing the antenna change-over I did another walk through and around the building with my laptop to see how the coverage had changed. The new antennas on the basement AP mean that I now have good coverage throughout our part of the basement -- and onto the loading dock and out to the spot in the garage where our cancer club members hang out. The signal held all the way out the side door and onto Talcott Street, where it finally gave up. As I was coming around to the front of the building, on Market Street, I expected to pick up the AP upstairs in our office much sooner than I did. I did some walking around back-and-forth out front and came to the realization that the signal died out about 20' from the building. That's not right, I thought.

This led me to my first successful wireless troubleshoot -- and not of the "I can't get XP to take my damn WEP key kind". Sitting in the cube of Mark my unindicted co-conspirator, NetStumbler was showing that the upstairs AP (about 30' away) was putting out a signal just 1% stronger than the other upstairs AP (in the upstairs wiring closet ~150' away, through two walls); not what I should have been seeing. First thought: maybe the ceiling-mount antennas are iffy. So, I got a ladder, unplugged the AP, changed the antennas for the little stubby ones I had just taken off the basement AP (always test with known-good parts), and powered it back up. No improvement. I pulled the AP down and swapped it with a spare. Zot! Was that a flood of microwaves I just felt coursing through my body? Indeed; the old AP's radio must have been going. The signal from the replacement was ~20dB stronger. As the Decibel scale is logarithmic, that means a 100x increase in radio power. Woo hoo.

I did another outside walk-about and was pleased to find that not only was I able to see the signal from 20' in front of the building, but also clear across Market Street at the old G.Fox building, and down the street to the Catholic book store. Now, someone might notice that we're actually trying to offer up some free wireless. Next step will be to hang another AP in our second floor conference center at the South end of the building. From there we'll reach more of Market St., and get the North end of Constitution Plaza. Better living through microwave radiation!

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