in contrast long wavelength magnetic transmissions (below 1 mhz) is not blocked or reflected by steel so nulls do not occur. the loop antennas may be detuned by the steel, just like higher frequencies. but, unlike higher frequencies, magnetic loop antennas may be re-tuned with external capacitors, and, in many cases, circuits can be created that dynamically pick the optimal external capacitor for the antenna. thus the de-tuning issue can vanish in a rubee network. but the tuning has to be set to the right frequency by adjusting the capacitor to match the tuning curve with steel in place.