The laboratory of heinrich hertz: Where circuit theory and field theory came together

The dipole antennas used by Hertz to demonstrate the propagation of electromagnetic waves in free space were of sufficiently small size electrically that their essential properties could be obtained from rudimentary equivalent circuits. Here we show computed time-harmonic properties of Hertz's transmitting dipole and receiving loop as well as their equivalent circuits. From this we determine the resonant frequencies that were essential to Hertz's work since the spark-excitation he employed resulted in radiation over a fairly narrow bandwidth near the first resonant frequency. Hertz used this resonant frequency f and the wavelength measured from standing waves to determine that velocity from the product v = f λ.