Driven By Curiosity

I was a little hasty in my board design. I did NOT do sufficient design of the RF section on my boards. What I find really funny now is that it’s much more obvious to me than it was previously. In lieu of a design, I copied the matching network from the CC2500 datasheet then copied some F-antenna from somewhere else. Not smart.

Looking at it now, the matching network is a 200 ohm to 50 ohm balun, the antenna is something else, although I really don’t know what. And the other prototype boards I’ve seen with a similar antenna have very different matching networks. Hmm… Oh well. It probably would have been clever to look around more and figure out how to do a 200 ohm folded dipole as suggested on the CC2500 datasheet.
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I noticed that I jumped into the middle of this project without much background. There are a couple higher-level posts, but nothing too specific. So…

This project started with the desire to create a simple device. The existing solutions are all complex in various ways. Generally they are a little pricey and are actually rather awkward to use as part of the business. That’s really the biggest issue. Technically they aren’t that exciting — something that blocks the starter signal in the car under certain circumstances. Not hard. A 50 cent switch from Home Depot would do fine, but not in the car finance business. “Now please place the switch in the off position until you pay us.” Not quite.

So obviously a little more is required. There’s a bit of range in implementations from punching codes in on buttons mounted in the car to pager-based enabling/disabling. The codes are easy (and inexpensive), but have an issue with distribution. Particularly when a finance company purchases the note from the dealer, there’s not really a guarantee that the customers will want to make payments solely at the finance company. The pager system makes distribution easy, on the whole, although you could have some coverage issues in places like New Mexico and it will cost you more. It probably depends on the value of the vehicle.
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