Do Spinning Bike Wheels Effect Reception?

[PopTopp]

I was riding my bike while holding my Garmin 60cs in my hand. (Please no safety lectures.) I noticed that as soon as I got any speed up, the map heading indicator would point 180 off my direction and the compass was nearly useless. When I stopped, the indicator would slowly align to the direction the unit was pointing. When held centered over the bike, I didn't have any problems.

 

Anyone else experience this and does anyone know why this happens?

[+mr007s]

I was riding my bike while holding my Garmin 60cs in my hand. (Please no safety lectures.) I noticed that as soon as I got any speed up, the map heading indicator would point 180 off my direction and the compass was nearly useless. When I stopped, the indicator would slowly align to the direction the unit was pointing. When held centered over the bike, I didn't have any problems.

 

Anyone else experience this and does anyone know why this happens?

 

I have mine handlebar mounted, both mountain and road bike. It functions the same as in my auto. have no idea why you are experiencing this. I do not see spinning wheels as the problem.

[+gpsblake]

I just had a conversation with someone who had a magnetic compass GPS'r unit hooked on their bicycle handlebars. They said it really messed with the compass and had to stop using it.

 

I don't have a magnetic compass on my GPS and it works perfectly on my bicycle over 1,000s of miles.

 

I suspect it's the metal throwing off the compass. I've heard of cases where magnetic compasses also will point to a car's engine when put in the car.

[+jacques0]

Are you using a cyclometer on your bike (speedometer, etc.?). If so, I wonder if there is an electrical field being generated by the rotating sensor (usually a magnet mounted on a spoke, and/or a circular magnet near the hub) on the bike wheel. It may be interesting to remove the sensor temporarily and try again.

[rickertk]

The magnetic field from a wheel magnet is pretty negligible. OTOH, if you've got steel handlebars or another major steel component, it will definitely mess up the compass, but no worse than if it hadn't been calibrated. As far as the OP's observations: when you're above a certain speed, the GPS won't use the magnetic compass, so that shouldn't have been an issue. When you say that the map heading indicator was pointing off your direction and the compass was useless, was the GPS aligned with your direction of travel? I'm hard pressed to explain your observation; I've had my GPS on my handlebars plenty with no odd effects on map heading except sometimes when standing still (if the compass was not well calibrated).

 

Keith

[PopTopp]

Don't have any gear on the bike. This only happened when I held the unit at the end of the handle bars, about 12 - 18" off the axis of the wheel. And no problems when the unit was centered or stopped. Thought it might have had some thing to do with a reflection off the spokes as they spun, dopler effects, etc. What we need is an electrical engineer with a background in antenna theory. Either that or a tin foil hat.

[PopTopp]

When you say that the map heading indicator was pointing off your direction and the compass was useless, was the GPS aligned with your direction of travel? I'm hard pressed to explain your observation; I've had my GPS on my handlebars plenty with no odd effects on map heading except sometimes when standing still (if the compass was not well calibrated).

 

Keith

 

I'd have the unit horizontal in my hand with the antenna pointed to the front. I'd be looking at the map display and that little triangle showing the direction the unit was pointing would rotate 180 as I picked up speed. When I stopped, it would rotate back to where I'd expect it to be.

 

Now you've got me wondering if I need to change my meds.

[peter]

Do you have the magnetic compass sensor of your 60CS turned on or are you just using the GPS-based compass? The magnetic sensor is very sensitive to how level the unit is held so I could see some effects just from that if you're trying to hold it while riding. Can't see that there would be any effect of the bike wheels on the operation of the GPS and have never noticed a problem with my Garmins in over 50000 miles of cycling use. But mine don't have magnetic compass sensors.

[Neo_Geo]

When was the last time the compass was calibrated? Maybe the magnetic compass is 180º out of calibrated alignment, and as you speed up over a certain speed, the GPS compass takes over the heading indication duties and begins displaying the proper heading...?

 

Is there a setting on the sensor models to have the display as North Up at a certain speed as well?

Edited April 15, 2006 by Neo_Geo

[+JohnnyVegas]

This only happened when I held the unit at the end of the handle bars

Turn off the magnetic compass and see if you have the same problem. As peter mentioned, if you do not hold a Garmin GPS that has a magnetic level it will not work properly.

[jackrr]

I had a similar problem with mine when I went geocaching with my motorcycle for the first time. When I would stop to get a bearing, my compass would be going nuts. At first I thought it was the ignition system of my dirt bike. But now I think that it was the electronic compass resetting itself. When I would stop it would take a couple of minutes before the electronic compass would come back on and then everything would be OK.

[PopTopp]

Thanks for the ideas. I'm heading out shortly and will see what's up after disabling the magnetic compass.