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.

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 page explains spikes in more detail.

When the transmitting beacon is 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 testing, the average distance from the strongest signal to the point over the victim was 1.4 meters on a three-meter burial and 0.85 meters on a two-meter burial. (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.

All this would be more manageable if there were only two or three points on the surface of the snow, but the two or three points shown above assume you are walking in a straight line (as would be the case if you are following the flux lines to the victim) and the beacons are precisely oriented. In the real world, these "spikes" appear as an oval on the surface of the snow surrounding 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 Ortovox S1, the Pieps DSP or the Pulse Barryvox as the receiving beacon, there was only one strong signal and it was always within a few inches of the point above the victim. Unfortunately, the three-antenna Ortovox X1 and Ortovox D3 behave like two-antenna beacons (in both my two- and three-meter tests, which I have done repeatedly on different occasions using different transmitting beacons). These two Ortovox beacons consistently display the shortest distance when over the spikes rather than when over the victim. That is unfortunate, because the only reason for a third antenna is to remove spikes from 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 (although it is likely you will encounter the victim before this time).

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.