Transceivers and Cell Phones

Hi All,

I was talking to a buddy the other day who was not aware of the potential for a cell phone to interfere with a transceiver, plus I was just reading some more comments about it in the YouTube comments section of the Northway/I-5 avy footage. So, for anybody who doesn't know, here you go.

My personal experience with a Pieps DSP and an iPhone 3GS is that I can get interference under the right conditions.

Under normal conditions, where your phone has a strong signal, you may have trouble observing any interference problems. However, when in a remote location with a weak or low signal - or perhaps when buried under snow - the phone will boost its output as it attempts to establish a connection to a base station. It's during this time when the potential for interference is highest. That can be exacerbated if the two are physically in close proximity.

I've made it part of my routine to turn off the cell phone when I turn on the transceiver.

Here is a thread that backs up my own observations.

www.tetongravity.com/forums/showthread.p...ae3d1618bdfa9f0efc6b

This has been a topic of a lot of BEER talks (sort of like TED talks but more often in a bar or parking lot). A grad student actually presented a paper on it at ISSW this year. Here's a link to a good synopsis, with a further link to the actual paper:
www.backcountryaccess.com/2012/11/19/iss...trical-interference/

My Pieps DSP will beep and display error code E04 when my smart phone (HTC 8X) gets too close -- even in transmit mode.

Probably best to have any sort of "radio transmitter" not transmitting while traveling in avalanche terrain -- if nothing else, taking the time to turn such devices off before starting a search wastes precious search time and worse if neglected could mis-direct the search efforts.

Might be interesting to test whether "airplane mode" avoids interference -- which would allow one to still use a smart phone for taking photographs, playing music, etc.

My Pieps DSP will beep and display error code E04 when my smart phone (HTC 8X) gets too close -- even in transmit mode.

Same deal as me; that's how I first figured out I was having issues with it (riding chair #6 or Northway at Crystal, or hiking in Southback, and hearing myself mysteriously beeping).

Probably best to have any sort of "radio transmitter" not transmitting while traveling in avalanche terrain -- if nothing else, taking the time to turn such devices off before starting a search wastes precious search time and worse if neglected could mis-direct the search efforts.

Might be interesting to test whether "airplane mode" avoids interference -- which would allow one to still use a smart phone for taking photographs, playing music, etc. 

Initially I was under the impression that Airplane Mode would fix this, but I just did some controlled tests with my iPhone 3GS and it does NOT prevent the issue. I get interference in Airplane Mode, for both search and transmit. In search, I get phantom readings if the phone is within a few inches. In transmit, I get E04 (interference). So, my take on this is to turn the phone OFF or keep it well away from my transceiver when traveling, then I'll turn the phone ON if I need to make an emergency call. The phones drain too quickly in low cell-signal situations anyway, and become inoperable if they get too cold (too far away from my body heat), so I'll keep mine on my person but powered off when in transceiver-transmit mode.

There's a more-general discussion about EM interference with digital beacons that we had last year near the bottom of the first page in the Weak Layers section:
www.turns-all-year.com/skiing_snowboardi...ex.php?topic=23345.0

The bottom line seems to be that it's a very real issue and you need to be attentive to what you have on you that may interfere with your digital beacon's ability to search. While YMMV, I found that powered-on electronic devices didn't greatly compromise the beacon's ability to transmit and be found, but it definitely had a noticeable impact in search mode. I'd like to put more quantitative analysis into it soon. When I do, I'll let you know what I find.

Backcountry Access affirms the connection in the FAQ found on their Tracker product pages:

www.backcountryaccess.com/product/tracker-2/

8th question down:

Do cell phones affect the Tracker?
Yes, but only if the items are extremely close to each other. Do not place cellular phones, communication radios, or any other electronic equipment within 12 inches (roughly 30 cm) of the Tracker DTS or Tracker2 while performing a transceiver search. In receive mode, irregular readings and decreased range can be caused by these and other sources of electrical interference, such as power lines, electrical storms, and electrical generating equipment. In transmit mode, keep the Tracker at least 1 inch (roughly 2 cm) from other electronic equipment.

My take away on all that stuff was basically that if you keep your transceiver at arm's length when searching you really shouldn't see any interference.

Wow, this issue hadn't even crossed my mind.... and even if I had, I wouldn't have thought that *airplane mode* would still do it. 

Thanks for sharing!