During deeper avalanche burials, the strongest signal is rarely directly above the victim. Beacons with fewer than three antennas (and some beacons with three antennas) will lead you to the strongest signal, which will be a point that is near, but not directly above, the victim.

Simple Spike Test

A simple way to see how well your transceiver handles spikes, albeit inaccurate, is to put a transmitting beacon on the ground, pointed vertically (the beacon on the ground shouldn't be a Tracker, because the transmitting antenna in Trackers is not inline with the housing). Then put your transceiver in Search mode and hold it against your chest (as high as possible where you can still read the screen). With your transceiver held horizontally, move extremely slowly looking for the location where the shortest distance is displayed (ignore the directional indicator if it is displayed). You should find the shortest distance almost directly over the transmitting beacon, but beacons with fewer than three antennas (and those with less than perfect firmware) will display the shortest distance when you are a foot or two away from the transmitter. This test shows whether your transceiver handles spikes at approximately one meter, but spike handling is much more obvious with deeper burials.

Probing Spikes

If your one- or two-antenna beacon leads you to a spike, you should still find the victim with good probing technique. For example, if you are within one meter of the victim and you probe using 25 cm (10 inch) spacing, you will need to probe approximately 65 times to completely check within one meter of the spike. If it takes 5 seconds per probe (a wild guess), it will take you a little more than 5 minutes to completely probe the area.

Detailed Spike Information

The distance between the strongest signal and the victim is based on the orientation of the two transceivers and the depth of the burial. These possibly confusing signals are the result of the flux lines and are called spikes. This section explains spikes in more detail.

When the transmitting and receiving beacons are on the surface of the snow, the receiving beacon will receive the strongest signal when it is directly above the transmitter. This is true regardless of the orientation of the two beacons and the number of antennas in the receiving beacon, because the transceivers are only a few inches from each other.

However, when the transmitting beacon is buried, this can change significantly. As shown below, when the receiving beacon has fewer than three antennas and is held horizontally, and the transmitting beacon is buried three meters deep in a vertical orientation, the strongest signal will not be over the buried beacon. Instead it will be a meter or more away.

The strongest signal is the result of the flux lines being transmitted.

The actual distance between the strongest signal and a point directly above the victim depends on many factors (primarily the depth and antenna orientation). In my spike testing, the average distance from the strongest signal to the point over the victim was 0.55 meters (21 inches) on one-meter burials, 0.85 meters (35 inches) on two-meter burials, and 1.4 meters (four feet) on three-meter burials. (This was with the transmitting beacon in a vertical position and the receiving beacon in a horizontal position as shown above.)

It gets more complicated. When both the transmitting and receiving beacons are horizontal, the strongest signals occur directly over the victim and a meter or more on either side.

If the buried beacon is neither vertical or horizontal (which is usually the case), the spikes appear at varying distances from the victim.

Three-antenna transceivers use the third antenna to analyze the flux lines and direct you to the point directly above the victim. When using the Barryvox Pulse, Ortovox S1, Pieps DSP, or Tracker2 as the receiving beacon, there was only one strong signal and it was always within a few inches of the point directly above the victim.

Unfortunately, the three-antenna Ortovox X1, Ortovox Patroller, and Ortovox D3, while better than two antenna transceivers, do not accurately resolve spikes (I've confirmed this repeatedly with one-, two-, and three-meter burials). These three beacons consistently display the shortest distance when over the spikes rather than when over the victim (although they were closer to the victim than two antenna transceivers). That is unfortunate, because the only reason for a third antenna is to remove spikes from deeper burials.

You can learn more about my spike testing here. You can learn more about multiple antennas here. You can read an article about dealing with spikes-and-nulls during deep burials here.