I was talking to a friend on the air about harmonics the other day and he was adamant that the first harmonic of a frequency was the fundamental frequency x 2. I was taught that the first harmonic was the fundamental frequency x 1. Which is it? https://www.amateur-radio-wiki.net/harmonics/ A Fundamental Waveform (or first harmonic) is the sinusoidal waveform that has the supply frequency. The fundamental is the lowest or base frequency, ƒ on which the complex waveform is built and as such the periodic time, Τ of the resulting complex waveform will be equal to the periodic time of the fundamental frequency. Is this question answered wrong? I looked immediately for 7.1 MHz or 7100 KHz but its not there.