Yagi Madness

Ok, so any of you who know me know that I am somewhat of a work- aholic. I always take my laptop with me on vacation. Our Colorado trip this year no different. But what is different is that this time I have a Sierra Wireless Aircard 595U. For those uninitiated to mobile broadband, this is an EV-DO card that plugs into my Macbook's USB port.

I was examining the Sprint coverage maps for Estes Park yesterday, trying to figure out what kind of coverage I would have. We are staying South of the city a few miles in a somewhat mountainous area. There is 3G service available about two miles NNE of our house, but coverage at the house is unknown. Windcliff Properties, who manages the house, warns tenants that the coverage is spotty. Not good for trying to use my aircard.

This morning I start reading about building yagi antennae. I read about the reflector, the directors, and the driven element; figuring out sizing and placement on the boom. All sorts of interesting information with limited practicality. I decide to build a yagi with 4 directors and figure out the dimensions for each of the elements based on the 1900MHz PCS frequency.

This did not turn out as well as I had expected. The first problem I ran into was that I couldn't find a connector locally to hook up to my Aircard. The lady at Rad Shack was nice and she thought she had the appropriate part; but no. Then I go to the Sprint store, and the lady there was not helpful at all.

• "It's not supported."
• "It doesn't work with CDMA technology."
• "You can damage the device."

I'm not sure what kind of damage I could do hooking it up to a passive antenna tuned to the right frequency, but I am guessing that is just their legal department covering themselves from people hooking the aircard up to amplified antennae.

Strike 1. But I have a plan. I remember that a similar connector is used to hook up Airport Extreme cards to macs. I have an old, broken Powerbook at the office and tear it apart, and bring the connector home. It doesn't fit.

Strike 2. I don't have a plan anymore. But I am going to continue to build the antenna just for the fun of it. I go ahead and pull out the soldering iron, the solder, the flux, and a couple of paper towels (ok, I know I should use a wet sponge, but its already not going to work, so what). I have drilled grooves in the wooden boom and super glued the elements in place. All I have to do is cut the coax and solder the coax to conductors to the driven element (DE).

Strike 3. It was a nice plan, but it didn't work out that way. The cheap soldering iron I bought is too hot for the outside conductor of the coax and burns it to bits, but is not hot enough for the copper DE, so I can't get a good solder joint. Instead, I use crimp connectors (but I know that's going to cause terrible reception. Oh well. I don't have a way to connect it to the air card anyway.

I'll keep the yagi in my archives; maybe someday I'll decide to tear apart the aircard and hardwire it for fun.

-rmz