Use Your Head? Exploring Configuration-Dependent Variation in Key Fob Range

Holding a remote keyless entry fob near the head provides a practical opportunity to investigate configuration-dependent changes in operating range. This pilot study examined five head-contact configurations in nine adults using a factory 433.92 MHz fob and its vehicle. Complementary assessments included an anatomically shaped skull phantom and 7 T magnetic resonance imaging (MRI). Operating thresholds were determined using a staircase procedure. The submental configuration yielded positive gains in all nine participants and the largest mean and median gains: 11.11 m and 12 m, respectively. The within-subject analysis identified an overall difference among configurations in eight complete cases (Friedman χ2(4)=23.24; Monte Carlo p<0.00001 based on 200,000 permutations; Kendall’s W=0.73). In the phantom series, each condition with distilled water yielded a higher gain than the condition with air at the same location, although gains did not increase consistently across fill levels. These observations identify promising configurations for further investigation. MRI characterized anatomical variation to inform future studies, with no significant associations after correction for multiple comparisons. Each condition was assessed once, and placement was evaluated with fob orientation and hand/body geometry. Building on these observations, repeated measurements with independent control of these factors will help establish repeatability and clarify the electromagnetic contributions.