Weird GPS/Computer Interaction
 

I have a Garmin Vista HCx mounted next to a Sigma BC1606L DTS wireless computer. I've always run the GPS on rechargeable NiMH batteries and everything worked well.

Yesterday I put alkaline batteries in the GPS and headed out for a ride. The Sigma absolutely refused to work- kept flashing the "Too Many Signals" msg. Didn't work for the whole ride.

Came home, put the NiMH batteries back in the GPS, and the Sigma immediately synced up and worked as it should.

So I know that NiMH batteries are 1.2v and alkalines are 1.5xv, but I just don't see how that could cause the effect I saw.

Theories?

I'm sure the GPS has a switching power supply in it. Any change in input voltage is going to change the duty cycle of the switching circuitry, resulting in different harmonic frequencies being generated. You just found a bad one for your situation.

Makes sense, I guess. Never would have expected it, though.
Thanks.