Avalanche Beacons and GPS Units

[iluka]

A friend of mine who works with S&R told me they've had some situations this season when they've noticed that GPS units are interfering with avalanche beacons in the receive mode.

 

Has anyone else noticed this?

[dmuja]

 

As far as I know (someone correct me if Im wrong), the common small GPS navigation unit people carry into the mountains does not *transmit* (it merely receives) a signal and therefore could not interfere with other signals.

 

Personal locator beacons (which are becoming more comon now days) and "Mt Hood MLU's" do however transmit a signal and therfore could possibly interfere with some RF receiver devices like an avalanche beacon. Also, cell phones send out a "ping" signal periodically which might also get picked up by other devices - possibly. If you get buried with your MLU/PLB going off along with your avy beacon or if your search partner is transmitting via MLU/PLB during a search, I could see that causing problems.

 

Anyway, according to some googling, GPS satellite transmit frequencies are 1575.42 MHz and L2 = 1227.6 MHz. Modern avy Beacon transmit frequency is 457khz. It might be possible for RF harmonic interference to "bleed through" across radio bands, but I highly doubt that the avy beacons are picking up satellites.

 

I guess I would be more concerned with turning cell phones PLB's/MLU's off while a search was underway.

[EWolfe]

I have never had a GPS unit interfere with the reception of my AVALANCHE POODLE!!!!

[mike1]

I don’t believe it has to be transmitting a signal to interfere with the magnetic flux of an avy beacon, though that could make it worse. I'm guessing it's more of an a function of magnetic flux lines from one electronic unit (GPS, Radio, TV, etc. Okay, maybe not a TV) affecting the flux lines of another (Avy beacon). I'd say just the mere chance of affect precludes keeping the units separated. More concern should be paid to what the GPS unit would do to the avy beacon if both were worn by the buried person. It may modify the flux lines enough to cause the searches to take more time in narrowing down that location. If you really want to know what happens, try it and see, then let us know what the results are.

 

Before the comments start coming in, I am obviously not suggesting anyone bury themself with the beacon and GPS to test this out. Simply burying it in a stuff sack will suffice.

Edited February 3, 2008 by Mikester

[dmuja]

 

 

You maybe right, though it maybe small, any electronic device does produce a concentration of electro magnetic waves and therefore could in theory interfere with other devices.

 

It might be a good idea to just turn off ALL (non-avalnche beacon) electronic devices when a search is underway.

[mike1]

I have never had a GPS unit interfere with the reception of my AVALANCHE POODLE!!!!

What if you and your poodle get buried together? Does she have an avy-lung or do you have to share your air?

[Ducknut]

I initially heard it was cellphones, but this article indicates all electronics. Linky

 

The other references listed have done some ad-hoc tests with other equipment that suggests that any electronic equipment can be bad.

[campwire]

GPS's definitely can interfere with avalanche tranceivers in receive mode. I experienced it personally while searching for the 3 lost snowboarders near Crystal. Once I realized I could be getting an erroneous signal (I searched in circles for about a minute), I turned off my other electronics one at a time, the culprit was my Garmin 76CSx GPS. It made my tracker give a reading of 30-35. Others experienced this as well.

 

This link isn't related to interference, but others may find it useful with regards to tranceivers.

 

http://www.beaconreviews.com/transceivers/

[112]

Is the amount of interference a function of screen size?