Figure 2.

Suggestion for implementing a fully blind protocol on behavioural experiments involving both the static geomagnetic field and RF fields, adapted from the experimental protocol of Ritz et al. (2004). (a–c) The orientations of the antenna that were used by Ritz et al. (2004); the RF antenna is in red and the direction of the local geomagnetic field is shown in blue. The position of the RF antenna loop and the power setting on the RF generator (located immediately adjacent to the experimental chamber) are different in each condition (control or ‘sham’). Macroscopic differences other than RF parameters among various test conditions can be eliminated by replacing the mobile loop of coaxial cable with three identical loops fixed in the desired positions, and then using a remote switch to determine which coil is energized. (d) The alternative situation with three fixed loops centred on the bird's cage with a remote switch near the RF generator used to select one of the coils. (e) A method for silently shorting out the RF field using a small reed relay, activated by an external control box. The method is to short across the 2 cm stretch of the outer conductor (the ‘screen’) that is removed on the far side of the RF feed, thereby yielding no RF output for the control or sham. This allows the power output on the RF generator to be run at exactly the same levels for all experiments. By implementing these measures, experimental conditions would not be obvious to the investigators in the room, which otherwise could possibly affect the animals.