Karoo keeps Bontrager trip computer from working

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    Keith Wakeham

    I looked up the 5W, its not an ANT+ or BLE device, and instead uses a proprietary signal method in the sub 1ghz region. However the hardware's FCC filings show no clearly distinctive antenna and the manual indicates 70cm MAX which is far from the meter's of range a typical ANT+ or BLE device would have.

    Considering the Karoo went through much much more stringent FCC / IC / CE certifications it seems unlikely that the cause of the problem is something the karoo is doing. Rather it might be placement due to the very very weak signal.

    Two suggestions. First is ensure the 5W is placed further away from the Karoo and as close as possible to the transmitter. The Bontrager manual insists on 70cm MAX (their all caps, not mine). Realistically for such a weak transmitter that is included with the 5W you'd want as much distance as possible from anything that contains metal or electronics. Secondly I'd suggest changing the battery. Weak analog transmitter will run for well beyond a useful time and if there is nothing obstructing you'd still get signal. Again the manual, FCC, and the pcb for this all point to a VERY weak analog transmitter that would likely be very susceptible to anything that would either detune it (metal, or other RF elements) or just even an old battery.

    Given this isn't a flaw with the Karoo, have you tried contacting Bontrager? They'll likely won't be able to give much guidance since this device dates back to 2005 (initial FCC filing) and  given it's very old and simple tech (19khz AM ping it looks like, not even "coded" by the looks) might be reflecting off of metal elements and knocking itself out. However, this really sounds way more like a Bontrager (actually Cateyes made it for Bontrager, which is a trek brand) problem.

    As a personal comment... that is the literal extremes of bike tech. Most high tech cycle computer next to the first "wireless" cycle computer. Fascinating.

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    Matt

    Thank you for your comprehensive comments, Keith.  The failure mode is that the Bontrager will sometimes, maybe every 30 or 60 seconds, briefly show a very high speed, resulting in a distance calculation that is well on the high side.  This makes me think that the Karoo is periodically emitting a series of RF pulses that the Bontrager mistakes as wheel rotations (magnet sensor chirps).  So, strangely, the problem is not that the Karoo is keeping the Bontrager from seeing wheel rotations, but instead is causing excess wheel rotations.  I'm thinking the solution is to pony up a few bucks and just purchase another trip computer.  I have had the Bontrager for quite a few years, so I got my money's worth!  

     

    Any specs I should be looking for in a new trip computer that would imply even better immunity to the Karoo's presence?  Thanks again, Keith.

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