Self Resonant Harmonics
A 120 uH coil self resonating at 8 Mhz. Surprisingly it also resonates at higher harmonics. This can be explained by viewing it as a transmission line rather than as an inductance and inter-winding distributed capacitance system. Of course if the end leads of the coil where connected to an actual capacitor it would only resonate at the standard LC resonant frequency.
Visualizing Coil Resonances with a Mercury Lamp:
The images showcase a coil resonating at its first four primary half-wavelength resonances. A clear silica-glass mercury-vapor lamp was tube placed along the coil to reveal the nodes within the standing wave pattern of the electric field. Â The helical geometry of the coil introduces dispersion effects, leading to the observed shift in resonant frequencies