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Discussion Starter · #1 ·
Every time I ride down this one road I notice my 30s power increases for seemingly no reason. It's in the first 2 minutes of my ride, I'm in a residential neighborhood so there's stop signs & traffic & I'm not trying to go hard. Now that I've noticed it I intentionally don't try to push harder & yet my power increases for about 15 seconds & the returns to normal. I looked at the power curve for that section & in every single ride I notice that my power spikes from 200w up to about 600w at the same point on the ride. After 15-20 seconds it returns to normal. Any ideas what would cause that? I'm using a Powertap Pro+ hub with a Garmin 500.
 

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Something external might influence the ANT+ transmission, e.g., some high-powered transmitters.
There's a section on one of my rides where lots of (mobile phone et.al.?) transmitters are mounted alongside the path and the cadence/power signal are lost.
It's rather annoying and lasts about 500m.
However, it seems unusual to actually get increased values.
 

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Discussion Starter · #4 ·
Temperature most likely. The newer ones won't have that issue.
Seems unlikely that temperature would affect the same 100 yards or so on the same road every day at various times of the day. I get that on the overall ride it's not a big issue but it seems very strange that any kind of interference could increase the power to the same extent every ride at the same point for the same period of time.
 

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No, it seems perfectly likely.

Your bike is inside, then it's outside. There's different temperatures.
Once it reads the temperature, it adjusts. Until then it's off.

Do you understand how temperature affects power meters?
 

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Discussion Starter · #6 ·
Do you understand how temperature affects power meters?
I understand a little. But my bike is not inside, then outside. The temp in my garage is within 2º of the temp outdoors.

Btw, I just checked a bunch of Garmin files & the same power spike happens on the same stretch of road on the return ride home. Power spikes to about 600w regardless of speed, cadence etc.
 

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I understand a little. But my bike is not inside, then outside. The temp in my garage is within 2º of the temp outdoors.

Btw, I just checked a bunch of Garmin files & the same power spike happens on the same stretch of road on the return ride home. Power spikes to about 600w regardless of speed, cadence etc.
sounds like RF Interference although I would expect that to causes a data dropout, not a reading.
 

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No, it seems perfectly likely.

Your bike is inside, then it's outside. There's different temperatures.
Once it reads the temperature, it adjusts. Until then it's off.

Do you understand how temperature affects power meters?
Temperature does not cause a 200% spike in wattage.
 

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Temperature does not cause a 200% spike in wattage.
That's exactly what it does actually when the wrong zero offset is set because of incorrect temperature or quick temperature changes.


Btw, I just checked a bunch of Garmin files & the same power spike happens on the same stretch of road on the return ride home. Power spikes to about 600w regardless of speed, cadence etc.
Well this pretty much throws temperature reading/self zero offsetting out of the window.

Sounds like a gremlin to me, probably living inside a telephone pole or something. Whatever you do, do not get any water on him.
 

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Are you sure none of your neighbors are space aliens?
 

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I understand a little. But my bike is not inside, then outside. The temp in my garage is within 2º of the temp outdoors.

Btw, I just checked a bunch of Garmin files & the same power spike happens on the same stretch of road on the return ride home. Power spikes to about 600w regardless of speed, cadence etc.
Hmm, I'm curious now, since this is very hard to explain indeed. I cannot think of any internal or external disturbance (other than someone intentionally sending out a signal that's meant to do this) that could cause this kind of consistent behavior. Can you try to just stop pedaling on that exact stretch, and see what your power readings say?

sounds like RF Interference although I would expect that to causes a data dropout, not a reading.
Exactly. What the OP is observing should not be possible; well, at least it should be astronomically unlikely to ever happen.
 

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It could be on the receiving end on the garmin side of things, if it's reading the ANT+ packet incorrectly. I've had some weird things happen on my 810 at specific locations, although not this specific problem. Maybe try riding the same route with the GPS turned off, or a different head unit if you have one.
 

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Every time I ride down this one road I notice my 30s power increases for seemingly no reason. It's in the first 2 minutes of my ride, I'm in a residential neighborhood so there's stop signs & traffic & I'm not trying to go hard. Now that I've noticed it I intentionally don't try to push harder & yet my power increases for about 15 seconds & the returns to normal. I looked at the power curve for that section & in every single ride I notice that my power spikes from 200w up to about 600w at the same point on the ride. After 15-20 seconds it returns to normal. Any ideas what would cause that? I'm using a Powertap Pro+ hub with a Garmin 500.
It's probably an errant electromagnetic signal, possibly containing digital wave forms, that when picked up by your receiver along with the signal from satellite, if I have this right, give consistently the same error readings.

Why not take another route, avoiding the place where readings are thrown off? Does it take place on different routes?

If its electromagnetic radiation, take another route. If not, its in the receiver unit.
 

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Do you have any other ANT+ sensors and if yes are they doing anything odd?

I'd borrow another head unit to see if it's the head unit, although I can't see how that would be the case.

Any signs for under ground cables near the road or high power lines overhead?

Last resort, wear tin foil on outside of helmet...... :)
 

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Do you have any other ANT+ sensors and if yes are they doing anything odd?

I'd borrow another head unit to see if it's the head unit, although I can't see how that would be the case.

Any signs for under ground cables near the road or high power lines overhead?

Last resort, wear tin foil on outside of helmet...... :)
Aluminum tin foil doesn't work! :D Person has to wear copper, lead, or steel, to acquire the necessary magnetic resistance to radio waves. They'll go right through aluminum!
 
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