I'm seriously considering buying a nice cycle computer/HRM, most likely a Polar s520 or s720i. However, I heard power lines can interfere with the wireless operation. I beleive 100% of the roads I ride on have power lines. Hell, I think most roads in S. Jersey have powerlines. How much of a problem is this? I don't want to spend $250 to $300 on a nice setup only to have it not work properly.

Thanks!

Mike

Ask at your LBS or someone who has one and rides in your area. It is impossible to answer defitely otherwise. Even in the best of areas there will be some interference from power transformers, signal light controllers, and other elctricals creating strong ElectroMagnetic field, and these will interfere with precision or downright disable the data sent from the transmitters. You can get wired computer to help that function, but I don't know of any wired HRM. Also the wired computers don't have many of the functions of the models you listed.

I think some of the higher end Polars like the S720i have coded transmitters so that should eliminate bogus readings. I think there's enough of an advanced descrimination circuit for them to cut through the electronic white-noise. My Shimano FlightDeck wireless (uncoded) computer can be effected by stray EMF but I literally have to be sitting on top of the source such as a traffic sensor pad at a stoplight. On my MTB which has electronically governed shocks (K2 SmartShocks) wireless is not an option because the EMF from the shaft position sending unit and the piezoelectric damping valves from the front shock play havoc with the wheel sensor so I use a wired harness. Powerlines on the other hand don't seem to effect it even when they're directly overhead. Honestly, I think you're safe buying it and then riding around your area. If you do observe a lot of sporadic readings then return it.

My S710i sure sometimes gets the kind of interference as I described, sometimes all readings stop, and if I look around, I usually see power transformer or other such source. one may not notice it, because the device generally recovers. It just depends upon how strong interference is there. If the receiver input gets overloaded, the coding will not help. That is there for similar strength interference, e.g. another rider.

My wireless Specialized Elite comp doesn't have a problem. I use it on my MTB but I cross a lot of powerlines where I ride and have never had interference that I'm aware of.

I ride near a lot of power lines (W&OD Trail in the Northern Viriginia Area). All the wireless HRM and cyclocomputers I tried have had problems due to them. Sometimes they would just cut out for a while and then start giving me readings again. Other times I would get really bogus readings (i.e., 104 mph).

It's hard to tell if you will have problems until you go out and try it.

I will say that since I switched to a *digital* wireless HRM I've had absolutely no problems with interference. Whereas before I had a problem on every ride. I got one of the Timex HRMs that specifically states that the transmission is done with a digital signal instead of an analog signal.

As for my cyclocomputer, I've just gone back to a wired model (Bike Planet 9.0). I do believe that there are some manufacturers that make a digital wireless model, but I can't remember where I read about it and I can't seem to find the link to one. If you are able to find one, please let us know because I would definitely consider going to one of those.

I know Polar and other cyclocomputers talk about having "coded" transmissions, but I'm not positive that will fix the problem if the transmission is still analog. All that is supposed to fix is your computer interfering with another computer (i.e., if your buddy is riding right next to you, you don't get his readings and vice versa).

As far as I know, the only thing that isn't affected by high power lines and stuff like that are wireless HRM/Cyclocomputers with digital transmissions.

Good luck.

I just bought a S520. However I live in San Francisco where power lines for the Muni are everywhere. I do get a drop off once in a while and erroneous readings. It happened with my previous Polar S150 (wired). It's the nature of the beast (wireless). On the flip side it is nice not having any wires! The S520 is an awesome tool for getting and staying in shape. I would never work out without it.

wow, this is a good thread, I'm looking into the s520 and I wanted to know just these things.... so It looks like i will be looking other places for tha HRM than polar. Has anyone tried the new cat eye hrm/computer?

thanks

And not only HRMs, regular cyclocomputers too. I was riding up a hill and came alongside some big "walking martian" electrical transmission towers and lines. As I was crawling up that particular hill, I was supprised to see my speed reading at 50+ mph.

Or maybe my brain was in high speed mode and it just seemed like I was going slow. . .

Thanks for the replies so far everyone. I confirmed on my last ride yesterday (a 25 mile loop I just started) that every road I ride, from backroad to highway (nice big shoulder), has powerlines.

P. B. Walker - Thanks for recommending the Timex HRM's. I'll seriously consider them, it's just too bad they don't have a bike specific model.

Both my bikes need service, so I'll find out what my LBS opinion is as well. They host Sat. morning rides, so I'm sure they know how much interference there is. If it's not too bad, I will go with one of the Polar's.