I have two heart rate monitor chest straps from Sigma and one from Garmin. Everytime I pass close by a trainline the numbers on my HR-Display go bananas. I'm about to go insane because of this, is there anything to do against this? Buy something new? Or throw it all in the bin..
Hmmm... I smell a science project! If the field is really strong be aware that optical may not work either because the chips/wireless probably aren't shielded anyway. Assuming you don't need laps for training, you could try hitting your lap button so at least you know when the event happens. I suppose you could try an experiment by taping aluminum foil to your chest covering the monitor pickups but not the wireless unit. That might tell you if the shielding issue is in the leads as I suspect or in the main unit that picks up the wireless. Ask yourself if the speed/cadence monitors wireless signals are being received to indicate whether an optical monitor might work.