Maximum wavelength in the band is for lowest frequency c = $v_{min}\lambda_{max}$ $\lambda_{max}$ = $\frac{c}{v_{min}}$ = $\frac{3 \times 10^{8}}{7.5 \times 10^{6}}$ = 40 m Minimum wavelength in the band is for highest frequency c = $v_{max}\lambda_{min}$ $\lambda_{min}$ = $\frac{c}{v_{max}}$ = $\frac{3 \times 10^{8}}{12 \times 10^{6}}$ = 25 m So, the wavelength band for tuning is between 25 m to 40 m.