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Do Electronic Devices Affect Beacons? Part 2 | Sisters, OR United States | 12/19/08, by powderjunky

Do electronic devices affect your beacon
This is a continuation of another article.  Click here for Part One.

In part one, we conducted stationary tests and found that only the GPS unit really affected the searcher beacon.  For part two we conducted an active search test.  Below are the results:


Our active search test to find out if electronic devices affect beacons.


Placing the victim and searcher 20 yards apart, we set up a control by doing a search with no electronic devices.  Both beacons in this test were BCA Tracker DTS.  Results: the searcher got a signal right away and was led straight to the victim.


GPS with Searcher
The GPS canceled out the victim's beacon and the searcher could not get a signal until about 7-10 feet away from the victim.  It then led the searcher away from the victim and the victim was never found.

GPS with Victim
The searcher beacon picked up a signal right away and led us to about 5 feet from the victim but then led us astray and the victim was never found.

Cell Phone with Searcher
The search path differed slightly than that of our control, but the victim was found in a timely manner.

Cell Phone with Victim
The search path was just a little different than the control but the victim was still found in a timely manner.

Summary
We did not get to test with walkie-talkies today because it got too cold outside.  However these results are on par with what we found during the stationary tests.  GPS = BAD! Keep those things at least a foot away from your beacon and best to just turn them off once you are about to ski!

Thanks for taking an interest in our first annual Beacon Week!  Be sure to check out the other articles from this week if you missed them.

Retire Your Beacon
Do Electronic Devices Affect Your Beacon Part 1
Does the Tracker Suck at Multiple Burials
Simple Answers to Difficult Questions, Beacon Technology 101




Simple Answers to Difficult Questio...
An Unknown Snowpack


That's Our Opinion. What's Yours?

Morten wrote on 12/20/08 at 3:21:12 pm pst:

Something must be missing in this story on how you tested this. How can a PASSIVE device like a GPS unit affect anything?


powderjunky wrote on 12/21/08 at 10:31:12 am pst:

Kind of weird, huh? We haven't left out any procedures or information. I don't know the technical part of this. I would like to say it's the electrical disturbance but then the cell phone and radio would have caused it to malfunction as well. Or maybe the GPS emits a different kind of electronic disturbance. In the manual the Tracker warns about holding any electronic device closer than 10 inches to your beacon. We'll try to ask the beacon companies and see what they say. Or maybe some who understands the inner workings of these things can chime in.


ChrisB wrote on 12/23/08 at 8:38:19 pm pst:

Most modern radio receivers emit weak signals on a number of frequencies, including the local oscillator (see http://en.wikipedia.org/wiki/Superheterodyne), the CPU clock, and from changing CPU execution patterns. Unless this circuitry is carefully shielded, it may be picked up by a nearby receiver and audible on an AM radio or analog avalanche beacon.

Testing with an Orotovox F1 Focus and a Garmin Etrex Venture EC GPS, I get a clearly audible signal on the Ortovox if they are within about six inches vertically or three horizontally. I get no audible effect from a Blackberry World Edition phone or a Spot Satellite Personal Tracker. With a Motorola LXT326 FRS/GMRS walkie-talkie, I get an effect within about one inch of the F1 if the walkie is in receive, or out to three inches in transmit. The intermodulation is enough to cause loud feedback if I put the F1's speaker within about an inch of the walkie's mic.

I suspect that simply listening to the beacon's receive audio is a more sensitive and objective test than trying a search pattern with a digital, though both are useful experiments.

I don't have a second beacon to test with, but I doubt that any of these devices will interfere with a nearby beacon's transmit function. Though it clearly could affect nearby receivers, and thus degrade pinpoint search for that beacon, as seems to be the case in the experiment video. So I'll keep my GPS in the top of my pack, which should be plenty of separation from the beacon under my arm.


powderjunky wrote on 12/23/08 at 9:08:48 pm pst:

Thanks Chris! Interesting to see the affects another a different beacon.


Jonathan S. Shefftz wrote on 03/10/09 at 7:28:33 pm pst:

First, the very title is misleading: you tested one particular model of beacon, not "beacons."

Second, in my testing with every beacon on the market, and all sorts of electronics devices, I have never experienced any interference with a transmission (i.e., interference from a victim's devices). And in my discussions with a few electrical engineers, they are highly doubtful that any ordinary consumer electronics could cause any such problems. I strongly suspect something is wrong with your testing protocol.

Third, onto the various devices when held by searcher (testing using four different models of beacons):

- GPS, with my Garmin 60Cx, the separation at which any effect disappeared was more like an inch or two, and the effect seemed relatively minor.

- Cell phone interference all depends on the cell phone. The band is probably not as important as the type of phone. For example, using a very basic CDMA-band phone (i.e., a phone that makes phone calls and doesn't do much else), the effect on most beacons is absolutely nothing. By contrast, a "Smart Phone" such as an iPhone has disastrous effects on all the beacons I've tested.

- An iPod causes very bad intereference with every beacon on the market.

- A small magnet (like on a refrigerator, or used on some gloves to keep them together) will turn a DSP from Transmit to Off or Search.


powderjunky wrote on 03/10/09 at 9:10:52 pm pst:

What can I tell you Jonathan, Just the results we found. The video shows exactly how we tested. Ideally it would be nice to test with all types of beacons, but since the Tracker is the most popular in the US we figured we would give it a try.

We are by no means experts on this, just skiers who like to get real life answers.

Thanks for sharing your research as well!



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