backcountry skiing Dynafit Trip Reports resort Misc Gear Reviews Louie weather Black Diamond safety Binding Reviews avalanches skins backpack climbing skins video snowmobile snowboard food clothing Fourteeners Boot Reviews camera huts Fritschi alpinism Utah avalanche safety photography alpinist guidebook Cloudveil Europe Silvretta Rando Racing Guest Blogs Technique kids Gear Mods Elk Mountains training Aspen automotive Wyoming computer Chris Davenport music backcountry skier Christmas 10th Mountain Enviro Rants bicycle North America Avalung TGR Austria GPS Mountain Culture north face Movie Reviews Everest Canada Book Reviews gloves batteries Aspen Mountain lightweight gear History News Backcountry Alps Andrew McLean Salewa Alaska Carbondale Maps Dave Downing first aid helmets Bob Perlmutter pastry Denver Google Aspen Highlands Montana Forest Service Sean Crossen Televangelism snowboarding Eulogies rock climbing Mount Sopris hunting Diamir Greg Hill Ortovox Craig Dostie Mike Marolt Aspen Skiing Company Boot Fitting thermo liner New Zealand

Jonathan’s WildSnow Beacon Test Notes

By Jonathan

Avalanche Beacons

Much of the basis for my reviews comes simply from lots of practice, often running searches in unusual or demanding circumstances. I’ve also run the beacon practice stations at various avalanche courses and ski patrol events, which provide an interesting opportunity to watch how other backcountry skiers react to different designs. I find this to be especially important, since often a feature that seems intuitively obvious to me will nevertheless baffle other users.

With that caveat aside, here are some brief descriptions of my formal testing. I also solicited feedback from all the beacon companies, and received very constructive information from all.

User Friendliness
The very first thing I do when I get a new beacon is try to conduct a search without reading the user manual. Now to some extent I’m already somewhat familiar with the beacon design from what I’ve read beforehand. But I feel that the ability to use a beacon without any user manual familiarity is a good test of the inherent ease-of-use of the design. (Plus how many typical users are really going to read their beacon’s user manual carefully?)

Electronic Interference (RFI)
I conducted three types of tests for potential electronics interference.

First, I set up a target beacon to transmit, and then set up a nearby semicircle of test beacons in search mode. I approached each beacon with a GPS, a digital camera, an FRS/GMRS radio, and a basic CDMA-band (e.g., Verizon) cell phone, one at a time. While doing this I noticed no changes in the searching beacons’ displays.

Then I repeated the testing with the FRS/GMRS radio and the cell phone making a call. Noticeable interference occurred in some, but not all models, with ghosting, distracting noise, incorrect directional indicators, and other problems.

Next, I added an iPod to the mix of devices: now the interference was much worse, and occurred in all beacon models. My conclusion: never tour in potential avalanche terrain with an iPod! The potential to have the iPod still on (yet not noticed) during a search could cause serious problems with any avalanche beacon.

I tested a “smart” phone, specifically an iPhone, which runs on the GSM band (i.e., AT&T). I changed my testing protocol this time to mimic my prior range tests for initial signal acquisition, i.e., start from far outside the acquisition range and then keep walking straight toward the target until a signal was acquired.

I held the iPhone (while making a call, although this probably doesn’t make any difference, since the actual cell transmission band is unlikely to be the source of the interference) close to the searching beacon. I tested three beacons, all of which fared far worse than with the previously tested electronics devices.

Specifically, the Pieps DSP immediately ghosted with its symbols for more than three victims, a distance readout of about four meters, and nonsensical directional indicators. I stopped the test right there, since clearly the actual victim would be impossible to find with that kind of interference.

The Ortovox S1 immediately yet briefly ghosted, but then the screen cleared . . . and stayed clear until I was less than four meters from the actual victim: this was even more scary, since the searcher would be entirely unaware of the interference problem.

The Barryvox Pulse ghosted, but seemed to fare a bit better than the others, although the interference was still a serious problem. Given the obvious problems caused by a “smart” phone, I didn’t bother testing any additional beacons. My conclusion: keep any “smart” phone entirely off while touring in potential avalanche terrain!

Lastly, I tested whether an iPod or iPhone could interfere with a victim’s transmission. Instead of merely placing the target beacon (which here was a Pieps Freeride) on the snow, an assistant held the beacon pointing toward me, but also held either an iPod or iPhone close to the transmitting beacon. My range results while searching with an S1, DSP, and Pulse were the same as when the beacon was on the snow with no electronic devices on either end. My conclusion: if you care only about yourself (i.e., your ease of being found), then feel free to play those tunes and chat away!

Box Size
My pinpoint phase accuracy test was inspired by an avalanche beacon review in the New York Times last year. As a native North Easterner, I feel obliged to take seriously everything the NYT writes, even on subjects where its editors probably know absolutely nothing. The NYT review commented on the large “box size” of one model, so I devised a test to attempt to replicate such results, as shown :

Avalanche beacon testing.

I suspect this would matter only if a full burial were somehow still relatively shallow. Therefore, although I report the results, and although they vary widely among beacons, I don’t think they’re very important.

Range
You would think range testing would be relatively straightforward. So did I. Wrong.

The first problem is what to count as initial signal acquisition. In general, I did not count a brief signal acquisition that then immediately disappeared (which often happens, i.e., a kind of brief “blip” that has you thinking, “wait, what was that?”). But if the acquisition was continuous, I then stopped my slow advance toward the target beacon to record the distance. By contrast, what to count as initial signal acquisition for analog acoustics is even far more subjective, but in general I counted a faint yet distinct “chirping” against any background sound.

Another problem is that the DSP, S1, and Pulse keep coming out with new firmware upgrades, which means having to run new range tests (as well as other tests). I appreciate their continuous innovation, but it sure complicates testing!

Next wrinkle is coupling – no, not that type of coupling (this is a family-oriented website!), but rather the orientation of the victim’s antenna (all beacons transmit on only a single antenna) relative to the orientation of the main axis of the searcher’s beacon’s housing (which can contain up to three receive antennas). So, do you test range during optimal coupling or worst-case coupling? My answer is, yes! In other words, I test for both, and report both, although I think worst-case coupling is more important, since it establishes the minimum range that you can rely upon consistently.

Backcountry Skiing beacon testing.

Multiple Burials (DSP, S1, Pulse, and 3 Axes only)

Multiple burial beacon test.

I have run many informal tests for the signal separation capabilities of the DSP, S1, Pulse, and 3 Axes, but I also set up the formal test diagrammed to right.

Looks like a nice controlled test, but unfortunately this is still subject to significant variation. Why? Read details here.

In [very] quick summary, because of ever-shifting signal overlap, each test was actually different, as each test beacon was facing a different set of signals with respect to their timing with one another. Nevertheless, after at least several trials with each beacon, consistent differences between models become apparent.

I also ran this fall’s version of the test with all modern beacons (i.e., D3, X1, Pulse in one test, then M2, Freeride, Pulse in another) and all old F1 Focus beacons for a worst-case scenario.

The Tricky Perpendicular Search
I set up a tricky perpendicular search to test the respective abilities of the Pulse’s 360-degree rotating arrow and the S1’s grid-like screen to accurately locate a beacon whose transmitting antenna is pointing directly at the searcher while the searcher is pointing at a 90-degree angle to the transmitting beacon. I also included a DSP in this test just to confirm my hunch as to how a “traditional” beacon with a more narrow arc of directional indicators would perform.

Imagine an avalanche path or deposition zone that is twice the width of a beacon’s range in worst-alignment coupling. The victim is buried at the extreme edge of the beacon’s range, with the transmitting antenna pointing toward the center of the slide path. The searcher enters the slide path with the beacon pointing toward the center. I attempted to replicate this scenario by approaching a target beacon that was pointed toward me, but with my beacon at a 90-degree angle to the target.

The Triangle Range Test
I set up a triangle range search to test see whether the impressively reliable marking/masking abilities of the S1 and Pulse compromise their respective abilities to locate another beacon toward the edge of their initial signal acquisition ranges. I included the DSP to see whether its less reliable marking/masking had the benefit of not compromising its ability to search for other beacons in a real life backcountry skiing avalanche accident.

Imagine a large triangle, with the searcher at one end, and a transmitting beacon at each of the other two ends (pointed toward the searcher’s end). The sides of the triangle are long enough to be toward the outer end of initial acquisition range (taking into account coupling alignment). The searcher walks toward whatever target the searching beacon gives priority. Once at the first beacon, that beacon is marked, and then the searcher sees whether the searching beacon can find the second transmitting beacon. If no signal is shown by the searching beacon, then the first target beacon is turned off, just to verify that indeed the problem with signal acquisition was caused by the focus on the first beacon, and not a range issue.

That’s it. If I can provide any clarification feel free to leave comments.

Posted by Jonathan on July 14, 2009 | Filed Under Avalanche Beacon Reviews, Jonathan Shefftz, Your Guest Blogs

Comments

6 Responses to “Jonathan’s WildSnow Beacon Test Notes”

Kevin July 14th, 2009 6:13 pm

In your write up I did not see a test of the iphone Avi beacon application that Wildsnow reviewed on April 1st :)

On a serious note I must say the mere thought of having a cell phone on while in the back country is troubling. But when I come down Vail pass and see all of the tracks on one of the more deadly exposures in this country it becomes more believable that folks would leave their phones on knowing they have coverage in this area.
Mark July 15th, 2009 8:43 am

Testing for interference with things like iPhones, iPods, cell phones, and the like is certainly smart. It is a little frightening to note how some of these devices foul up beacons’ functions.
Andy_L July 15th, 2009 10:29 am

Lou & Jonathan,

The interference info is critical stuff! Linked over to you, and I’ll try to remember to bring it up again when winter’s here.
Jonathan Shefftz January 3rd, 2010 9:48 pm

I recently ran some add’l RFI tests, with some interesting results, both concerning new devices and new beacons (or rather, combinations I hadn’t previously tested of new devices + old beacons).

First, previously I had found that a CDMA (Verizon) basic phone (i.e., makes phone calls and does nothing else) does not cause interference when on yet not transmitting, and does cause interference when transmitting. However, this time I happened to notice that the phone briefly causes interference when being flipped open, even when not making a call.

Second, previously I had been unable to detect any interference from a Garmin 60Cx GPS unit. This time though I tried the GPS when some old M2 and F1 beacons (which are generally not the subject of my various tests). When held very closely, the GPS caused interference.

Third, a tried a Spot satellite messenger, second generation. When on, but not attempting to send a message, no interference. When transmitting a message, caused interference in some beacons.

Overall, my conclusions from all this are that:
- RFI issues can be very specific to certain beacon + device combinations; and,
- RFI is often not caused by transmission but rather by power issues.
Bruce Cheshire March 31st, 2010 2:38 pm

Was the iPhone ‘on’ during your test? Did you happen to test it with the Airplane mode on?
Jonathan Shefftz March 31st, 2010 7:01 pm

The iPhone was on, but not making a call.
Given that my electrical engineer friend thinks the interference has nothing do with the signal, and instead is related to the power step-down (apologies if I mangled the techno talk there), then I strongly suspect that the airplane mode would still produce the same interference.