Can anyone provide detail or insight into the Heart Rate Monitors that are sold for personal use - such as those sold by Polar (and others)? Typically a chest strap is worn - the chest strap contains some electronics that ultimately transmits a pulse for each heartbeat detected. The receiver, often worn on the wrist (or bike handlebar) receives the pulses then counts, displays, etc.
I was able to "listen" to the transmitted pulses with my AM radio held within a few feet of the strap (while it was on me). Then I took a coil of wire and connected the coil to a scope and I could see the pulse waveform if I held the coil reasonably close to the chest strap. It appeared that the transmit frequency was fairly low- maybe 100 kHz but with no storage or synch capability I had to guess.
At the same time I was having trouble getting decent readings from my monitor while on some equipment in the gym - apparently because of the rather large amount of electronic noise. I had contact a couple of manufacturer's reps for HRMs to see if anyone made one that was more immune to the noise however the reps barely understood my question. One offered that the IC used in their receiver was the same as everyone else used (only one made) so that it was unlikely any one brand or model would be superior - not sure if true.
Ultimately I'd like to solve this problem. One thought was to contruct a repeater that would be attached to the chest strap or my belt. I thought I'd post the situation here to see what others might know.
I was able to "listen" to the transmitted pulses with my AM radio held within a few feet of the strap (while it was on me). Then I took a coil of wire and connected the coil to a scope and I could see the pulse waveform if I held the coil reasonably close to the chest strap. It appeared that the transmit frequency was fairly low- maybe 100 kHz but with no storage or synch capability I had to guess.
At the same time I was having trouble getting decent readings from my monitor while on some equipment in the gym - apparently because of the rather large amount of electronic noise. I had contact a couple of manufacturer's reps for HRMs to see if anyone made one that was more immune to the noise however the reps barely understood my question. One offered that the IC used in their receiver was the same as everyone else used (only one made) so that it was unlikely any one brand or model would be superior - not sure if true.
Ultimately I'd like to solve this problem. One thought was to contruct a repeater that would be attached to the chest strap or my belt. I thought I'd post the situation here to see what others might know.