| Author |
Topic |
North Vancouver, BC
Canada
1607 Posts |
Posted - 03/03/2012 : 10:56 PM
|
I was doing a quick skin trip in very safe terrain to test out a boot fit today. I was by myself but had my beacon (an Arvo EVO3+) on me out of habit.
Out of curiosity, I put my beacon in search mode and it started to pick up a signal. That was odd since I was sure I was by myself and the terrain was very safe. I left it in search mode and started moving but the results were fairly nonsensical. Later on, I put it back in search mode and got similar results. I pulled my iPhone out of my pocket and identified it as the culprit. The interesting thing is that it didn't seem to matter if it was actively transmitting or not - the entire time the phone was on it was providing interference.
It's likely that any active beacons would have overpowered a lot of this interference but I'd have to experiment more to be sure. However, if I wasn't sure how many people were caught in a slide this ghost signal could have had me searching for a very long time for phantom victims.
I recently took the AST-1 and I don't believe they mentioned this. If they did, it certainly wasn't emphasized.
I will now be adding a "turn off all cell phones and other electronic devices" step to any search and I'll probably leave my phone off and not put it in my chest pocket. |
|
Vancouver
1820 Posts |
Posted - 03/03/2012 : 11:17 PM
|
That's very interesting. I must experiment with this for range, tone etc. If it has any range at all, it could be an emergency backup for people caught in avalanches who don't have transceivers. Phoning the buried party probably would cause a distinctly different noise.
Any electronic gizmo powered on or in standby mode emits emf. Try tuning an AM radio between stations and put it close to your computer. Not only will you get lots of noise, it will change depending on what the computer is doing. Even the AM radio itself puts out emf. Tuning one AM radio to a frequency a certain amount of frequency different from what another AM radio is tuned to, will "jam" the other radio.
I wouldn't be surprised if an led headlamp puts out emf.
And people worry about smart electricity meters. |
|
|
North Vancouver, BC
Canada
1607 Posts |
Posted - 03/03/2012 : 11:24 PM
|
quote:
Originally posted by sgRant
If it has any range at all, it could be an emergency backup for people caught in avalanches who don't have transceivers.
Interesting idea but I don't think the range is that good and there is no hope of experimenting in my home (way too much interference from everything.)
quote:
Originally posted by sgRant
I wouldn't be surprised if an led headlamp puts out emf.
I have now read that some headlamps have a warning that they can interfere with beacons. |
Edited by - Steventy on 03/03/2012 11:24 PM |
|
|
Vancouver, BC
Canada
874 Posts |
Posted - 03/03/2012 : 11:38 PM
|
Modern headlamps maintain constant power to the LED regardless of battery level, by pulsing the power using an SCR (silicon controlled rectifier) aka PCM (pulse control module). The on/off pulses are quite rapid (1-10 msec) and have very fast rise/fall times which generates lots of electrical noise.
If you look closely at snow falling by headlamp, the snowflakes will look like short dashes rather than continuous lines due to the headlamp strobing on and off. |
Edited by - weedWhacker on 03/04/2012 09:28 AM |
|
|
Finally stopping that crazy suffering that is ice, climbing to concentrate on great ski tours!
3506 Posts |
Posted - 03/04/2012 : 09:01 AM
|
I had my Tracker in the chest harness, and my E-Trex hanging on a lanyard around my neck. The Tracker keep making strange beeping noises. Took me a while to figure the GPS was somehow interfering with the beacon. Switched the GPS off, no more noises.
Now I have my beacon in the special beacon pocket in my pants, and it seems like that is enough distance (before the two devices were almost on top of each other) as my Tracker works perfectly when I use my GPS now. |
|
|
Whistler, BC
Canada
1174 Posts |
Posted - 03/04/2012 : 10:00 AM
|
quote:
I recently took the AST-1 and I don't believe they mentioned this. If they did, it certainly wasn't emphasized.
We always stress this in our programs. It's a widely known phenomenon. Add digital cameras to that as well, Ipods, etc. |
|
|
Burnaby, BC
Canada
1297 Posts |
Posted - 03/04/2012 : 10:18 AM
|
I remember reading somewhere that the 457kHz avalanche beacon frequency was chosen specifically because it's close to a commonly used electronic intermediate frequency, avoided by other transmitting devices, to prevent long-range interference.
But that the intermediate frequency proximity causes spurious errors when placed close to a lot of other electronic devices.
Tracker 2 user manual cautions keeping other electronic devices at least a foot away in search mode. |
|
|
Richmond, BC
Canada
2441 Posts |
Posted - 03/04/2012 : 11:14 AM
|
quote:
Originally posted by msulkers
quote:
I recently took the AST-1 and I don't believe they mentioned this. If they did, it certainly wasn't emphasized.
We always stress this in our programs. It's a widely known phenomenon. Add digital cameras to that as well, Ipods, etc.
Despite it being well known, is there now a warning in the printed information of all new beacons?
Check your documentation and forward your concerns to the manufacturer if indeed it's not identified in the documentation.
Other than GMRS radios, I leave my electronics turned off on trips untill I really need to use them to conserve power (Obviously the Avi beacon is the exception).
Maybe do a test of each item seperately and note the distances between units when interference begins and dissipates to nil.
Here's a valuable report done by the editor at Wild Snow. Very enlightening
http://www.wildsnow.com/1609/jonathans-wildsnow-beacon-test-notes/
Also this one is a good article for points to follow:
http://beaconreviews.com/transceivers/Interference.asp
Until a search is completed, keep the non essential electronics turned off untill you need them or turn them off immediately following the accident.
VHF/UHF radios and GMRS radios shouldn't be an issue unless there is constant traffic on the radio. In which case It would be an idea to switch to an alternate dedicated frequency for your search period.
just my thoughts |
Edited by - pmicheals on 03/04/2012 11:17 AM |
|
|
North Vancouver, BC
Canada
1607 Posts |
Posted - 03/04/2012 : 11:58 AM
|
Thanks all. Great info.
quote:
Originally posted by johngenx
I had my Tracker in the chest harness, and my E-Trex hanging on a lanyard around my neck. The Tracker keep making strange beeping noises. Took me a while to figure the GPS was somehow interfering with the beacon. Switched the GPS off, no more noises.
Now I have my beacon in the special beacon pocket in my pants, and it seems like that is enough distance (before the two devices were almost on top of each other) as my Tracker works perfectly when I use my GPS now.
The trick will be to remember to turn off your GPS (or maybe to switch places and put it in your pants pocket) when you are executing a search.
If I am ever in a search where I am looking for an unknown number of burials or if it is not clear if they were using beacons, I will be extra diligent about turning off all electronics.
On the plus side, this trick can be a great way to freak out less experienced partners around a campfire while winter camping.
Step 1: Say that you forgot to turn off your beacon and confirm that everyone else turned their beacons off.
Step 2: Grab your beacon and put it in search mode.
Step 3: Convince everyone that you are not alone in the woods and lead them away from the light of the camp fire to find the source of the signal. As it gets darker pull the beacon closer to your chest to make the frequency of the beeps increase.
Step 4: Scream in horror as if you found something horrible or someone is attacking.
Step 5: Sleep lightly because payback is coming.
|
|
|
North Vancouver, BC
Canada
1607 Posts |
Posted - 03/04/2012 : 12:05 PM
|
quote:
Originally posted by pmicheals
quote:
Originally posted by msulkers
quote:
I recently took the AST-1 and I don't believe they mentioned this. If they did, it certainly wasn't emphasized.
We always stress this in our programs. It's a widely known phenomenon. Add digital cameras to that as well, Ipods, etc.
Despite it being well known, is there now a warning in the printed information of all new beacons?
Check your documentation and forward your concerns to the manufacturer if indeed it's not identified in the documentation.
Other than GMRS radios, I leave my electronics turned off on trips untill I really need to use them to conserve power (Obviously the Avi beacon is the exception).
Maybe do a test of each item seperately and note the distances between units when interference begins and dissipates to nil.
Here's a valuable report done by the editor at Wild Snow. Very enlightening
http://www.wildsnow.com/1609/jonathans-wildsnow-beacon-test-notes/
Also this one is a good article for points to follow:
http://beaconreviews.com/transceivers/Interference.asp
Until a search is completed, keep the non essential electronics turned off untill you need them or turn them off immediately following the accident.
VHF/UHF radios and GMRS radios shouldn't be an issue unless there is constant traffic on the radio. In which case It would be an idea to switch to an alternate dedicated frequency for your search period.
just my thoughts
Good articles. It looks like the iPhone/iPod is particularly bad. |
|
|
Vancouver, BC
Canada
1321 Posts |
Posted - 03/04/2012 : 1:50 PM
|
I was just looking at the guide for the Mammut Element, and it does include the following:
Avoid having other electronic devices (e.g. mobile phones,
radios, headlamps), metal objects (pocket knives, magnetic
buttons), or other transceivers close to your running avalanche transceiver. |
|
|
Langley, BC
Canada
1078 Posts |
Posted - 03/04/2012 : 2:21 PM
|
quote:
Originally posted by tu
I remember reading somewhere that the 457kHz avalanche beacon frequency was chosen specifically because it's close to a commonly used electronic intermediate frequency, avoided by other transmitting devices, to prevent long-range interference.
But that the intermediate frequency proximity causes spurious errors when placed close to a lot of other electronic devices.
Tracker 2 user manual cautions keeping other electronic devices at least a foot away in search mode.
455KHz is a pretty standard intermediate frequency for AM radios. Referring back to sgRant's post, if you tune one AM radio to 455 KHz higher than another radio, you may be able to pick up interference. This won't work with digital radios that tune in 10KHz increments.
quote:
Originally posted by weedWhacker
Modern headlamps maintain constant power to the LED regardless of battery level, by pulsing the power using an SCR (silicon controlled rectifier) aka PCM (pulse control module). The on/off pulses are quite rapid (1-10 msec) and have very fast rise/fall times which generates lots of electrical noise.
n
If you look closely at snow falling by headlamp, the snowflakes will look like short dashes rather than continuous lines due to the headlamp strobing on and off.
They would surely use a MOSFET (metal oxide semiconductor field effect transistor, not an SCR.
This is done to take advantage of a physiological phenomenon whereby a pulsed light appears brighter than a constant intensity light source of the same average power. |
|
|
Kamloops, B.C.
Canada
157 Posts |
Posted - 03/05/2012 : 09:40 AM
|
| I was doing some beacon practice with a couple buddies who want me to take them ski touring. We were getting some strange signals, never thought to check their cell phones. I had forgotten about that. Thanks |
|
|
Vancouver
1820 Posts |
Posted - 03/06/2012 : 08:56 AM
|
As a result of the concerns raised in this topic, I did some testing. For transceivers, I used two Ortovox F1's. The results do not necessarily have any validity for newer, fancier tranceivers.
One transceiver was sending, the other was receiving. Against them, I tested: a cheap portable AM radio, a Garmin Hcx GPS, a Blackberry 8330 cell phone, an led headlamp, and a digital camera.
I did not test the phone while making a call with it.
All of the gadgets, including the transceivers, when powered up and placed within 6" of the AM radio, caused some white noise on the radio. The headlamp had only a tiny effect, while the cell phone had the most effect in the form of various white noises as the phone changed functions. Later I'll get back to what the transceivers did to the radio, since it's quite interesting.
None of the gadgets had any effect on either of the transceivers if the gadget was turned off. I know the camera, gps and phone have a little background activity even when shut off, but this had no noticeable effect on the transceivers.
The radio, powered up, did not affect the sending or receiving transceiver.
The headlamp had no effect on either the sending or receiving transceivers, even when in direct contact.
The cell phone, camera and GPS produced a slight buzz on the receiving transceiver, but only when within 6" and never enough to impair the use of the transceiver's led's or sound signal.
Perhaps the most interesting thing is that the AM radio picked up the sending transceiver's signal. The strength depended on the distance, orientation and tuning. I didn't try many frequencies because I don't expect to be doing this in the field, but at the 900 setting the radio could pick up the transceiver over 10' away. I didn't try the FM or shortwave bands.
Another point is that people play with and test transceivers in buildings, which are dense with emf interference, and don't report any particular problems.
The bottom line is that I'm not going to worry about this degree of interference. But I would also not claim this has any validity for any other model of transceivers, GPSs, phones etc. or cell phones being used to transmit. |
Edited by - sgRant on 03/06/2012 09:17 AM |
|
|
Richmond, BC
Canada
2441 Posts |
Posted - 03/06/2012 : 2:49 PM
|
quote sGrant
quote:
Perhaps the most interesting thing is that the AM radio picked up the sending transceiver's signal. The strength depended on the distance, orientation and tuning. I didn't try many frequencies because I don't expect to be doing this in the field, but at the 900 setting the radio could pick up the transceiver over 10' away. I didn't try the FM or shortwave bands.
If you moved around the room with the radio tuned to the tranceiver frequency, were you able to DF on the tranceiver and/or notice any increase/decrease in signal? just curious
|
|
|
Vancouver
1820 Posts |
Posted - 03/06/2012 : 4:20 PM
|
quote:
Originally posted by pmicheals
quote sGrant
quote:
Perhaps the most interesting thing is that the AM radio picked up the sending transceiver's signal. The strength depended on the distance, orientation and tuning. I didn't try many frequencies because I don't expect to be doing this in the field, but at the 900 setting the radio could pick up the transceiver over 10' away. I didn't try the FM or shortwave bands.
If you moved around the room with the radio tuned to the tranceiver frequency, were you able to DF on the tranceiver and/or notice any increase/decrease in signal? just curious
I didn't try it for direction finding. There was a clear difference in volume to indicate distance with the radio held in orientation. Given what the AM aerial looks like, it you should be able to determine direction with it.
The transceiver frequency is not on the AM band. Hopefully someone will correct me, but I think 457 is about half of 900 where I found good reception AND no radio station. It makes sense that a harmonic of the source frequency could be sensed by the radio. This should show up at the multiples of 457. |
|
|
North Vancouver, BC
Canada
1607 Posts |
Posted - 03/06/2012 : 6:21 PM
|
Thanks for doing a test!
quote:
Originally posted by sgRant
The cell phone, camera and GPS produced a slight buzz on the receiving transceiver, but only when within 6" and never enough to impair the use of the transceiver's led's or sound signal.
It sounds like it wouldn't be an issue in most scenarios with your equipment.
There is still one scenario that requires extra caution: if you are searching a debris field and you don't know how many (if any) people are buried. If your GPS is hanging around your neck, it would be pretty easy for it to be 6" from the transceiver and it could make you think that there may be a faint signal coming from the debris field when really there is no one there.
quote:
Originally posted by sgRant
Another point is that people play with and test transceivers in buildings, which are dense with emf interference, and don't report any particular problems.
For reference, I have a very hard time finding a place in my apartment where I don't get interference. |
|
|
Vancouver
1820 Posts |
Posted - 03/06/2012 : 6:28 PM
|
quote:
Originally posted by Steventy
There is still one scenario that requires extra caution: if you are searching a debris field and you don't know how many (if any) people are buried. If your GPS is hanging around your neck, it would be pretty easy for it to be 6" from the transceiver and it could make you think that there may be a faint signal coming from the debris field when really there is no one there.
But the thing no one has said is that the transceiver signal could hardly be a more distinct "beeping" noise, while the white noise sprayed out by electronic equipment is totally different. There is just no way to confuse the two, and the white noise is too weak to mask the beeps. Suggesting the GPS, or whatever, creates noise on the transceiver that impairs hearing signals from other beacons is like saying you can't tell what someone is saying if there's music playing in the background. |
|
|
North Vancouver, BC
Canada
1607 Posts |
Posted - 03/06/2012 : 6:44 PM
|
quote:
Originally posted by sgRant
quote:
Originally posted by Steventy
There is still one scenario that requires extra caution: if you are searching a debris field and you don't know how many (if any) people are buried. If your GPS is hanging around your neck, it would be pretty easy for it to be 6" from the transceiver and it could make you think that there may be a faint signal coming from the debris field when really there is no one there.
But the thing no one has said is that the transceiver signal could hardly be a more distinct "beeping" noise, while the white noise sprayed out by electronic equipment is totally different. There is just no way to confuse the two, and the white noise is too weak to mask the beeps. Suggesting the GPS, or whatever, creates noise on the transceiver that impairs hearing signals from other beacons is like saying you can't tell what someone is saying if there's music playing in the background.
Depends on the beacon. Mine is digital and displays a number that represents the approximate distance to the victim and I believe it generates its own beep which makes it much harder to tell if it is noise or real. I can run some tests later but I seem to remember that it was very easy to generate a fairly strong indication of a victim at a distance of 20m when my iPhone was in my pocket. It was basically indiscernible from the output I would get if a real beacon was placed 20m away. I will have to run tests to confirm.
My main concern is not when other beacons are present. I suspect that real beacons would overpower interference for analog or digital receivers. My concern is when you are in a scenario and there are no other beacons but you are fooled into thinking one might be out there.
|
|
|
Langley, BC
Canada
1078 Posts |
Posted - 03/06/2012 : 6:45 PM
|
quote:
Originally posted by sgRant
The transceiver frequency is not on the AM band. Hopefully someone will correct me, but I think 457 is about half of 900 where I found good reception AND no radio station. It makes sense that a harmonic of the source frequency could be sensed by the radio. This should show up at the multiples of 457.
This is correct, and I was going to say something about it earlier. There are a number of ways the distortion could be created in either the avalanche transciever or the AM radio. |
|
|
Vancouver
1820 Posts |
Posted - 03/06/2012 : 7:06 PM
|
quote:
Originally posted by Steventy
quote:
Originally posted by sgRant
quote:
Originally posted by Steventy
There is still one scenario that requires extra caution: if you are searching a debris field and you don't know how many (if any) people are buried. If your GPS is hanging around your neck, it would be pretty easy for it to be 6" from the transceiver and it could make you think that there may be a faint signal coming from the debris field when really there is no one there.
But the thing no one has said is that the transceiver signal could hardly be a more distinct "beeping" noise, while the white noise sprayed out by electronic equipment is totally different. There is just no way to confuse the two, and the white noise is too weak to mask the beeps. Suggesting the GPS, or whatever, creates noise on the transceiver that impairs hearing signals from other beacons is like saying you can't tell what someone is saying if there's music playing in the background.
Depends on the beacon. Mine is digital and displays a number that represents the approximate distance to the victim and I believe it generates its own beep which makes it much harder to tell if it is noise or real. I can run some tests later but I seem to remember that it was very easy to generate a fairly strong indication of a victim at a distance of 20m when my iPhone was in my pocket. It was basically indiscernible from the output I would get if a real beacon was placed 20m away. I will have to run tests to confirm.
My main concern is not when other beacons are present. I suspect that real beacons would overpower interference for analog or digital receivers. My concern is when you are in a scenario and there are no other beacons but you are fooled into thinking one might be out there.
You're absolutely correct. I keep forgetting that I need to add the proviso to every comment I make that I'm not addressing the more modern transceivers. Surely someone has done some serious research into this? Europe? |
|
|
|
Topic |
|
Avalanche beacon interference by cell phones
