In recent years, avalanche transceivers have undergone further technical development and a lot has also happened in terms of training. Searching with an avalanche transceiver has never been as easy as it is today.
Nevertheless, users are often confused, especially during intensive training scenarios. Namely when – rarely, but nevertheless – the avalanche transceiver displays direction or distance information that is incorrect. In rare cases, a ghost signal is even registered, i.e. there is a signal even though no beacon is transmitting.
On the one hand, this is due to the technology, as even the most modern avalanche beacons can be disrupted by electromagnetic fields in search mode. In SEND mode, on the other hand, metallic objects can reduce the range.
On the other hand, ski tourers and freeriders are often not sufficiently aware of this problem. This is exacerbated by the fact that many more electronic devices are carried on tours today than in the past.
Things to note in SEND mode
In SEND mode, metal objects and electronic devices in the immediate vicinity of the avalanche transceiver reduce the range of the device. Even the aluminum packaging of the muesli bar can affect the transmission power; larger metal objects (e.g. Leatherman, belt loop, etc.) that are very close (< 5 cm) to the avalanche transceiver are really relevant. These can reduce the transmission power by up to approx. 30 percent.
The same applies to electronic devices: the closer they are to the avalanche transceiver antenna, the greater the impact on the range. Incidentally, it makes no difference whether the smartphone is in flight mode, for example, or whether telephony, Wi-Fi and Bluetooth are active.
To prevent such a restriction of the transmitter range, all metal objects and electronic devices are stowed at a distance of at least 20 cm from the avalanche transceiver.
Because in the event of an avalanche burial, more distant pockets can also lie next to or on top of each other, it has proven to be a good idea not to stow the avalanche transceiver together with other items of equipment, but to carry it on the opposite side of the body.
If the transmitting antenna is nevertheless disturbed by metal parts or electronic devices, a transceiver from teh company PIEPS recognizes this and automatically switches to another antenna using the Auto-Antenna-Switch.
Note: Metal parts integrated in clothing and gloves (magnetic buttons, heating elements, etc.) must be avoided.
Things to note in SEARCH mode
In SEARCH mode, the avalanche transceivers are even more sensitive than in SEND mode and must be seen as a highly sensitive receiving device.
Other electronic devices – e.g. a smartphone in the vicinity – can lead to incorrect direction and distance information, reduce the reception range and thus the search strip width or provoke the aforementioned “ghost signals”.
For this reason, a generally recommended minimum distance of 50 cm between the avalanche transceiver and possible sources of interference applies in SEARCH mode. It is even better to switch off the relevant devices, as the distance can quickly fall below the 50 cm safety distance if, for example, a GoPro is mounted on the helmet and activated. The same applies to smartphones, because even in SEARCH mode, it makes no difference whether the flight mode is active or not in terms of interfering signals.
Because smartphones are usually responsible for confusing “ghost signals”, it is ideal if everyone searching with their avalanche transceiver switches off or hands over their cell phone. While this is easily possible with a larger group of rescuers, a single rescuer will often have to keep their communication device switched on in order to remain reachable for the emergency services. The respective situation therefore determines what is possible. In any case, it is important to keep the problem of these “ghost signals” in mind.
Speaking of emergency calls: In an avalanche field, the person raising the alarm should be positioned at least 25 m away from the avalanche transceivers with their cell phone or satellite device, while all other people switch off their communication devices.
Note: Digital avalanche transceivers have a highly sensitive receiver in order to receive and display even weak signals. However, this also makes them susceptible to interference, e.g. if a smartphone increases the background noise of the receiver, causing incorrect information to be displayed or the search strip width to be reduced. The top devices from most manufacturers therefore have an analog mode for advanced users, which clearly displays a “real” avalanche beacon signal even if there is a lot of background noise.
Summarized recommendations
- SEND mode: Always stow possible sources of interference (metal objects & electronic devices) at least 20 cm away from the avalanche transceiver and on the opposite side of the body.
- SEARCH mode: Anyone searching for a buried victim with the avalanche transceiver must switch off their smartphone and other electronic devices if this is possible in the given situation. Alternatively, the devices must be stowed at least 50 cm away from the avalanche transceiver.
- All other people in the avalanche cone switch off their electronic devices or use their smartphones at least 25 m away from the searcher.