Thread: frs/gmrs radio effection on avalanche beacon?

I had a question for you folks. I recently purchased two frs/gmrs radios for BC skiing so we could radio back and forth when people had made it to the bottom or to safe zones. I vaguely remember reading something that said that cell phones may interfere with your beacons signal and make it hard for you to be found if you are burried (if your cell phone is turned 'on'). I think it was my barryvox manual that said that. Since I dont have the manual anymore, does anyone know if frs/gmrs radios cause this same problem? Anyone know to what extent the radio signals are messed up? I just want to make sure that no one is placed in additional danger because they have their twoway radio turned on while riding down the mountain.

I'm sure you're gonna get a lot of good responses on this. I'll just throw in that on patrol we wore the beacon on our back and the radio in front to keep the signals apart...

Ummm why don't you test it?

turn on beacon to search, leave one on send. then turn a radio on near one, then the other, then talk near one, then near the other, etc.

The "reports" I've seen the issue is RECEIVE mode (i.e. when searching) -- a cell phone very close to the receiver can interfere with the signal. So when searching turn off radios.

First of all, replace your manual from this link. I just tried the beacon in proximity to two Motorola T6530 radios and got no response in the receive mode with the radio on, or transmitting. I would say they don't likely interfere in a way that would slow a search. Different radios could have different results. FYI, I use the switchable analog / digital mode, and did not pick up a signal in either. A cell phone, computer, GPS and other electronic devices have shown interference.

effection?

Originally Posted by Snow Dog

The "reports" I've seen the issue is RECEIVE mode (i.e. when searching) -- a cell phone very close to the receiver can interfere with the signal. So when searching turn off radios.

Exactly.


We are talking about 457,000hz beacon vs a 462,550,000hz-467,725,000hz radio that is 0.5W-3W depending (most are 0.5W-1W).

It depends on the beacon and the quality of the radio (unintentional emissions by the radio that the beacon then fails to filter or discriminate against). Cheaper radios are more likely to have the issue.

The problem most likely will manifest if the FRS/GMRS radio is transmitting, not just idly sitting there. For the buried person with a radio tramsit button stuck down, the range at which a spurious emission would become noticable on searchers beacon is within 1m when the searcher would be probing anyway.

For the searcher, the radio would not be stuck in transmit so any interference *should* only last as long as you are talking on your radio.

Based on my limited knowledge and some experiments

What about the wider debate about cellphones and beacons? Most of my friends want to turn the phones off while skiing but nobody's really sure if it's a problem.

Please ignore and point me to the previous TGR debate on this topic if there already is one.

Is the best solution to test with actual devices (often) and see? But then again for example when I receive an SMS, if my phone is neaby an audio amplifier I'll get ticking sounds - all other times it's fine...

Just kind of nice to get text messages while you're away for the day skiing...

There's no reason a 2 GHz phone should interfere with a 487 KHz receiver but I guess a lot of devices are sloppy with interference in off-frequency bands?

Any studies or other "hard evidence" on this subject?

The only guidance in the barryvox manual is "Avoid in general that there are electronic devices (i.e. cellular phones) or metal parts (i.e. pocket knife or magnetic buttons) in close proximity to a transceiver which is turned on." OK, I imagine that an FRS/GMRS radio would fall into the 'electronic devices' category. The question becomes what is close proximity? Are we talking about putting a beacon on your back and radio on the front as SheRa suggested, or are we talking about them being seperated by several feet or meters? I always turn off my cell phone for this reason, but if I'm using a radio to communicate up/down mountain with members of my group I would prefer to be able to just leave the radio on, rather than trying to play the game of the person with the radio off is the person skiing, then they turn it on to radio back, then the next person turns theirs off. I guess that would be one way to fix things when taking turns down the slope, but it still doesnt solve the issue of communication with the person in the rear communicating with the person up front (if you are spread out over a 1/4 mile or so with a larger party) because you would need to leave the radios on full time. From what I've noticed about 1/2 the avalanches are created when skinning up to the peak, not the actual ride down..therefore the radio question has some large importance as to whether you can leave it on while traveling or not and how far it really needs to be from yoru transciever to be safe.

I would assume that a 800Mhz/1.9Ghz phone would be the same as my post above. Most are 0.6W (some do 3W).

The problem with beacon-electronic doodad is every combination is different. A modern gizmo, like an iPod, has a microprocessor and oscillator and generates a little rf. It's the same with a radio -- most use a superheterodyne receiver which has an oscillator and leak a little rf. Will it be a problem? Try it at home and find out. If it's ok at home then it's ok in the field. A good transceiver designer will have tried all those things and minimized the interference.

I'd guess most of the time "close proximity" means inches. I can see the problem with patrollers since most radio harnesses put the radio on the chest where the transceiver goes.

the only problem you would have is in the receiver (search mode beacon), it would be possible for another strong signal to get into the receive chain of the (search beacon) and get mixed in to the signal. (the signal interfering signal can actually be picked up by the electronics, i.e. bypass the filers, get mixed down with the transceiver signal and fup the results).

with cellphones there is really no way to test this (since they are frequency/time hopping and varying output power), with GMRS etc you can test this by: them on then radio and whistle into it, then see if it causes a problem for the receiving beacon. (this would have to be done on all the channels of the radio, (not sub channels) and at very close range).

The interference could/should only happen at rather short range, and I do not think that it will be a problem.

the actual frequency differences of a 457Khz beacon and a 450Mhz help prevent interference, the interference is still possible is the interfering signal is strong enough, (I really do not think 5-10 watts is at any real range).

when I patrolled last season I had the beacon in front and the radio in front and had no problems searching, the only problem finding a beacon that I ever had was when there was a light pole with a light that was on in the vicinity of the burried beacon which I circled like 5 times. That was embarassing.

OTOH my beacon will create audible interference on my VHF radio and my cellphone...

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power transmission lines will screw with your stuff. i've watched digital beacons become short ranged and very confused. analog beacons don't become confused, but their ranged is still diminished.

Ansel Adams says try not to get into slides under these:

Originally Posted by Summit

OTOH my beacon will create audible interference on my VHF radio and my cellphone...

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power transmission lines will screw with your stuff. i've watched digital beacons become short ranged and very confused. analog beacons don't become confused, but their ranged is still diminished.

Ansel Adams says try not to get into slides under these:

Looks like the backside of Steven's Pass

BCA tech rep recommended to me that it's "good practice" to keep 12 inch distance between beacon and radio/cell - but that it really didn't matter

Remembering from my Avi I... I believe it is possible for nearby metal objects to function as antennas... this could include ski poles... and would lead to a larger CEP for your pinpoint search, though not significantly (assuming you have a probe)