I remember about 30 years ago wearing one of those halter monitors after I thought I was having some sort of heart problem. Turns out it was diagnosed as premature atrial contractions, supposed to be pretty common. Back then it was a pretty heavy thing with a leather strap around my neck sort of like a women's handbag and the device itself was like one of those cassette tape recorders and it did have a tape so it actually was a cassette recorder. I had to walk around with that heavy thing for 1 week in the ICU.
Fast forward to today's date and I have the latest and greatest heart monitor device on. They still call it a halter monitor but without the halter or tapes. Now the recorder is all solid state and about the size of a cell phone and it sits in my pocket. Technology marches on. They did tell me to keep away from microwave ovens when in use since it might scramble the data. At that moment, I thought about asking about strong RF fields from HF or VHF or UHF transmitters but, I kept quiet since I knew it would be useless and a waste of time trying to explain what I was talking about - Ham Radio. The long leads from my chest would probably be resonant to some frequency so I'll play it safe.
So, I decided to take a 24 hour break from transmitting and just listening on the SW bands. I can pull this thing off tomorrow morning. All I gotta say, is these damn sticky things on my chest start to itch it will come off quickly.