I'm looking for feedback on people experiencing problems with intermittent drops outs with Stages Power Meters. Particularly if you encounter problems with drop outs with a watch type device like the Garmin 910XT or 920 when worn on the wrist.
I got a Stages PM about 2.5 yrs ago to train for IMFL 2015. It seemed like a reasonably priced approach, and it was "compatible" with my Garmin 910. I got the left crank only, to keep the $ down, and to allow me to "easily" swap between road and Tri bikes.
Well, all went very well when I was training since I would always take the time to mount the Garmin on the handlebar when in training. Never had any problems with drop outs. Then my first tri came. Since it was a sprint, I didn't bother to take the time to mount the Garmin, and left it on my wrist after the swim. Imagine my surprise when the power trace looked like a long line of pumpkin teeth!
After calls to Garmin and Stages and the oft reported "It's THIER problem!" I read somewhere or maybe Stages told me about mounting the Garmin on the handlebar, particularly on the left side, the same as the crank. This got my rusty old engineering brain cranking. I no longer have access to the type of electronic measuring devices that would allow me to prove my hypothisis, but here's what I think is going on.
First a short course of antenna theory.
Antennas have ideal patterns based on a lot of factors, far too complex to explain here. But lets start by thinking about two perfect "point" antennas.
The pattern for this type of antenna is a sphere, radiating out from the point equally in all directions like the sun, and decreasing rapidly as the distance to the between the points increases. The initial power of the transmitter (the power meter) determines the maximum effective range. Increasing power output to the antenna however decreases functional battery life, so a balance is struck.
In addition, there are design strategies that can take the available power and focus it in certain directions. This will in effect extend the useful range at any give battery power usage rate. I believe that stages has designed their transmitting antennas ( google Transmitting Antenna Patterns for example) as perhaps a very thin Dipole. THis pattern would be like a very flat donut or a cd platter..
Receiving antennas can also be designed to "look" in certain directions to improve performance. Now lets assume for purposes of explainaiton of this situation, that the Garmin has a similar pattern, a flat disk.
So now lets think about the orientation of these two patterns based on position of the Garmin wrist vs handlebar.
IF the Garmin is on your handlebar and the receiving antenna patter is like a 5 foot CD, and the transmitting antenna pattern Stages on the crank is another 5 foot CD, it is easy to see that the patterns would intersect constantly and provide a reliable connection.
Consider now having the Garmin on your left wrist. The intersection would be spotty at best.
I'm convinced that, while the actual patterns might be different than I've outlined here, this describes the basis of the problem.
I know it doesn't help any of us who have a similar set up, but perhaps someone might be able to offer a 3rd party solution to enhance the pattern(s) and improve performance.
Or we can just go out and get new devices, particularly ones specifically designed to work together.
As for me, I'll stick with my current set up. For Sprints I don't much care about bike power, for international distance I can hold the garmin in my hand. For long course I'll just take the few seconds to strap it on the handlebar. Then, when the time comes, I'll get a unified system.
I got a Stages PM about 2.5 yrs ago to train for IMFL 2015. It seemed like a reasonably priced approach, and it was "compatible" with my Garmin 910. I got the left crank only, to keep the $ down, and to allow me to "easily" swap between road and Tri bikes.
Well, all went very well when I was training since I would always take the time to mount the Garmin on the handlebar when in training. Never had any problems with drop outs. Then my first tri came. Since it was a sprint, I didn't bother to take the time to mount the Garmin, and left it on my wrist after the swim. Imagine my surprise when the power trace looked like a long line of pumpkin teeth!
After calls to Garmin and Stages and the oft reported "It's THIER problem!" I read somewhere or maybe Stages told me about mounting the Garmin on the handlebar, particularly on the left side, the same as the crank. This got my rusty old engineering brain cranking. I no longer have access to the type of electronic measuring devices that would allow me to prove my hypothisis, but here's what I think is going on.
First a short course of antenna theory.
Antennas have ideal patterns based on a lot of factors, far too complex to explain here. But lets start by thinking about two perfect "point" antennas.
The pattern for this type of antenna is a sphere, radiating out from the point equally in all directions like the sun, and decreasing rapidly as the distance to the between the points increases. The initial power of the transmitter (the power meter) determines the maximum effective range. Increasing power output to the antenna however decreases functional battery life, so a balance is struck.
In addition, there are design strategies that can take the available power and focus it in certain directions. This will in effect extend the useful range at any give battery power usage rate. I believe that stages has designed their transmitting antennas ( google Transmitting Antenna Patterns for example) as perhaps a very thin Dipole. THis pattern would be like a very flat donut or a cd platter..
Receiving antennas can also be designed to "look" in certain directions to improve performance. Now lets assume for purposes of explainaiton of this situation, that the Garmin has a similar pattern, a flat disk.
So now lets think about the orientation of these two patterns based on position of the Garmin wrist vs handlebar.
IF the Garmin is on your handlebar and the receiving antenna patter is like a 5 foot CD, and the transmitting antenna pattern Stages on the crank is another 5 foot CD, it is easy to see that the patterns would intersect constantly and provide a reliable connection.
Consider now having the Garmin on your left wrist. The intersection would be spotty at best.
I'm convinced that, while the actual patterns might be different than I've outlined here, this describes the basis of the problem.
I know it doesn't help any of us who have a similar set up, but perhaps someone might be able to offer a 3rd party solution to enhance the pattern(s) and improve performance.
Or we can just go out and get new devices, particularly ones specifically designed to work together.
As for me, I'll stick with my current set up. For Sprints I don't much care about bike power, for international distance I can hold the garmin in my hand. For long course I'll just take the few seconds to strap it on the handlebar. Then, when the time comes, I'll get a unified system.
