Antenna's suck?

If I stop running and start walking, I'll have my watch down near my hip.  My heart rate disappears.  It will find it again if I hold my wrist up next to my chest strap.  I thought the problem may have been due to an old strap,  so I picked up a new Run strap.  No change.  When riding my Core indoor trainer I have to take my watch off of my wrist and place it to my right side (the same side that the guts of the trainer are on) for my watch to pick up power from the trainer.  Any thoughts?