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Calibration and Sensor Tuning Parameters

The RotorHazard timing system allows you to calibrate each node individually, so that you can compensate for the behavior and hardware differences across your system and environment.

Each node keeps track of the signal strength (RSSI) on a provided frequency, and uses the relative strength to determine its position relative to the start/finish gate. A node can be crossing or clear. If a node is clear, the system believes the quad is not near the start/finish gate. If it is crossing, the system believes the quad is passing by the start/finish gate and a lap pass will be recorded once the crossing is finished.


Parameters that affect the crossing status are EnterAt, ExitAt, and RSSI Smoothing.


The system will consider a quad to be crossing once the RSSI raises to or above this level.


The system will consider a quad to have finished crossing once the RSSI value drops below this level.

RSSI Smoothing

Adjusts the filtering on the RSSI value, to reduce noise. Less noise creates cleaner data that triggers more easily, but delays the response time of a node. Too much smoothing could prevent high-speed passes from being recorded. Apply higher smoothing indoors.


Before during any of the other tuning procedures:

  1. Power up the timer and keep it running for a few minutes to allow its modules to warm up. (The RSSI values tend to increase by a few points as the timer heats up.)

  2. Power up a quad and bring it very close to the timer for a few seconds. This will allow the timer to capture the peak-RSSI value for that node. This should be done for any node/channel that is being tuned.

The Capture buttons may be used to store the current RSSI reading as the EnterAt or ExitAt value for that node. The values may also be entered and adjusted manually.

Set the EnterAt value:

  • High enough that it is only reached when the quad is near the start/finish gate.
  • Not so high that a quad cannot reach it as it approaches the start/finish gate.
  • Higher than ExitAt.

A good starting point is to capture the EnterAt value with a quad about 5–10 feet away from the timer. If gate crossings are being missed then lower this value. If gate crossing are triggered when they shouldn't be then increase this value.

Set the ExitAt value:

  • Low enough that RSSI noise during a gate pass does not trigger multiple crossings.
  • High enough that that the quad will always drop below the value at some point on the course. (The lowest value recorded since the last pass is displayed as the Nadir.)
  • Lower than EnterAt.

A good starting point is to capture the ExitAt value with a quad about 20–30 feet away from the timer. If a pass by the timer is resulting in multiple crossings, try lowering this value. If the 'Crossing' indicator is stuck on, try increasing this value.

If crossings are still erratic, increase RSSI Smoothing to reduce noise. (A smoothing value of 0.001 has been found to work well in indoor environments.) Placing a metal shield around the back of the timer can help.

Sample RSSI Graph:

Sample RSSI Graph


  • Try to keep EnterAt and ExitAt further apart than the size of noise spikes/dips.
  • Dropping below the EnterAt value during a pass is fine, as long as the level stays above ExitAt.
  • Spiking above ExitAt after a pass is fine, as long as the spike doesn't reach EnterAt.
  • Increase RSSI Smoothing to reduce the amount of noise.
  • A very low ExitAt value (but above the Nadir) will still work, but the system will wait until it is reached before announcing laps.
  • Actual timing uses raw RSSI values collected within the crossing window, irrespective of Smoothing. Heavy smoothing does not affect lap times, but could prevent high-speed passes from registering as crossing.
  • The Minimum Lap Time setting can be used to prevent extra passes, but might mask crossings that are triggered too early.


Laps registering on other parts of a course:

  • Raise EnterAt until crossings only begin near the start/finish gate

Many laps registering at once:

  • Raise EnterAt, if possible
  • Lower ExitAt,
  • Increase RSSI Smoothing

Laps taking a long time to register:

  • Raise ExitAt

Node is never crossing:

  • Lower EnterAt

Node is never clear:

  • Raise ExitAt

Missing high-speed passes:

  • Decrease RSSI Smoothing