Originally Posted by OPC
Take a look at the Garmin Edge 305. Units are available with HR, Cadence, or both. GPS tracks speed, altitude, %Grade, and other stuff. It can also operate with the GPS turned off for indoor training.
The interference thing may be just electrode contact with the skin. Performance Bike carries an electrode gel (H.S.E.) that has made a world of difference for my HRM. No more wiggy 200+ BPM readings.
As I understand it, a GPS for measuring speed can be less accurate if you do much turning so I think I'd like a more normal way of measuring that - though a GPS has some nice things on top of that.
As for the interference, I know some of it comes from my headlight because of many tests. If I turn off the light, the readings seem to make sense. If I turn it back on, the numbers steadily increase every time. I use foil to make this problem more intermittent, but it still happens.
Then there are some spots where it consistently gives false readings even with the light off. Since it seems to be in the same area each time, it seems there must be something in that area doing it rather than a problem with skin contact. Still, I can see that getting the stuff you mentioned may be of help. Thanks for that info.