This can happen for example when the free space wavelength exactly equals the lattice spacing.
2.
In this case the circumferential ( wavelength ) scaling must be used, remembering that this is the wavelength within the transmission line and may differ from the free space wavelength.
3.
For example, at a frequency ? = 20 MHz ( free space wavelength of 15 m ) in a transmission line whose velocity factor is 2 / 3, the guided wavelength ( distance between voltage peaks of the forward wave alone ) would be ? = 10 m.
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