Wireless Computers & Interference

[Rivermist]

I have had a wireless computer for a few weeks now, it has always worked fine.

Today on a ride I was stopped at a big intersection with several traffic lights overhead. I glanced
at my computer to check out my average speed and noticed that the speed was not zero. In fact it was
changing about every second 37.4... 14.2...7.6....0....25.2.... and so on, just random numbers. I
noticed that the timer was running as well.

At first I was thinking I would be returning it to Performance where I bought it, but then on all
subsequent stops it did not do that.

There were no other cars or bikes next to me. I assume there was some kind of interference from the
traffic light overhead.

Anyone else had this experience?

 

[DiabloScott]

I assume there was some kind of interference from the traffic light overhead.

I once pulled up next to a parked car and my heartrate monitor went berzerk - it said 280bpm I think (something outrageously high) and started beeping. I think the security system in the parked car had something to do with it but I don't know why. Traffic lights don't typically have any radio frequency transmitters but they usually have a sensor that picks up a signal from emergency vehicles (so the light changes to green when the fire truck comes). There may also have been some kind of police or media camera to monitor the intersection that could have used RF for one reason or another. Who knows? Interference is generally isolated and short IME.

 

[benshemuel]

I ride the San Francisco Bay Area subway -- BART -- frequently and <i>always</i> have interference problems with my computer - a Specialized Speed Zone Pro. It picks up some sort of impulse noise from the train motors and has recorded speeds as high as 80mph! Screws up my odometer reading, of course.

I have tried sticking it in an antistat back, which helps but doesn't completely eliminate the problem.

Wireless bike computers are <i>not</i> sophisticated radio devices.

 

[benshemuel]

I ride the San Francisco Bay Area subway -- BART -- frequently and always have interference problems with my computer - a Specialized Speed Zone Pro. It picks up some sort of impulse noise from the train motors and has recorded speeds as high as 80mph! Screws up my odometer reading, of course.

I have tried sticking it in an antistat back, which helps but doesn't completely eliminate the problem.

Wireless bike computers are not sophisticated radio devices.

 

[benshemuel]

I ride the San Francisco Bay Area subway -- BART -- frequently and always have interference problems with my computer - a Specialized Speed Zone Pro. It picks up some sort of impulse noise from the train motors and has recorded speeds as high as 80mph! Screws up my odometer reading, of course.

I have tried sticking it in an antistat bag, which helps but doesn't completely eliminate the problem.

Wireless bike computers are not sophisticated radio devices.

 

[unknown]

Try sticking it in an iron box. AFAIK, wireless bicycle computers obtain their signal magnetically
rather than by radio.

-harold

benshemuel ([email protected]) wrote:
: I ride the San Francisco Bay Area subway -- BART -- frequently and always have interference
: problems with my computer - a Specialized Speed Zone Pro. It picks up some sort of impulse noise
: from the train motors and has recorded speeds as high as 80mph! Screws up my odometer reading,
: of course.

: I have tried sticking it in an antistat bag, which helps but doesn't completely eliminate the
: problem.

: Wireless bike computers are not sophisticated radio devices.

: --
: >--------------------------<
: Posted via cyclingforums.com http://www.cyclingforums.com

 

[benshemuel]

Harold:

Interesting suggestion, although after struggling to reduce my bike's weight by 20 grams here and 10 grams there I'm a little reluctant to carry an iron box.

Your point about them working magnetically is interesting. There's no FCC reg number on either the sender or the computer, which adds credibility to your suggestion. I'll see if I can get any useful info out of Specialized.

B

Originally posted by unknown
Try sticking it in an iron box. AFAIK, wireless bicycle computers obtain their signal magnetically
rather than by radio.

-harold

 

[harold]

Something like a Strepsils or Altoids tin will provide enough shielding to stop the computer
working on the bars, so it may be sufficient for your purpose. These tins are of course steel that
is tin plated.

I believe the signal frequency is only about 5KHz, and at these small distances it is the magnetic
field propagated that dominates.

-harold

benshemuel ([email protected]) wrote:
: Harold:

: Interesting suggestion, although after struggling to reduce my bike's weight by 20 grams here and
: 10 grams there I'm a little reluctant to carry an iron box.

 

[benshemuel]

Great suggestion, Harold, I'll give it a try. I presume Strepsils are some sort of British mint entity?

Ben

Originally posted by harold
Something like a Strepsils or Altoids tin will provide enough shielding to stop the computer
working on the bars, so it may be sufficient for your purpose. These tins are of course steel that
is tin plated.

I believe the signal frequency is only about 5KHz, and at these small distances it is the magnetic
field propagated that dominates.

-harold