I've had intermittent performance over the past year with my Cateye wireless bike speedometer/computer, (see "Why I am sometimes not so enamored of short RF links" and the user comments for more details). After a few emails, the vendor, Cateye, has decided the problem is likely a defective transmitter (sender) unit and is sending me a replacement. Let's hope that does it.
Since the unit is likely a single IC with lots of epoxy potting, there wasn't much I could do it diagnose or fix it, nor did I want to spend my time doing so. Plus, the signal has a very low repetition rate, 0.2 clicks/sec per mile/hour of speed (about 0.1 click/sec per km/hour), which makes any sort of signal-capture on a scope very challenging.
But I was still curious about the frequencies, formats, and protocols used for these types of units. I did a lot of web searching, and came up empty. I found out othing about the frequency, modulation, enclosing, anything that is used by this vendor, or any other vendor.
I wonder: why is this? What's the big secret? Is there an industry standard, or does each vendor have a different internal design standard? Are they afraid of hackers? Or are they concerned that other vendors will use their "sender" but sell different readout and display units? Or is it just a habit and tradition to keep information like this a secret?
I'm thinking that it may be like the ubiquitous infrared (IR) remote control, where every TV vendor developed a different format and protocol. The reasons, some say, were that each vendor thought theirs was a little better, more reliable, and less power hungry. Maybe so, there's no way to really know.
But others say that TV vendors wanted a proprietary situation, to lock users in to using their remote and thus have a hold on the potentially lucrative replacement market for when you lost or broke the remote that came with the TV. That tactic worked for a while, but within a few years, you could buy a "universal" remote for $10-$15 (but they are a pain to program to your system's codes, I speak from experience!).
Meanwhile, if anyone knows anything about the frequencies, coding, or format used for the bicycle computer, I'd be interesting in hearing about it. It's tough to put that technical curiosity to rest. ♦