In situ measurements of equatorial electron density irregularities in the F‐region by rockets and satellites have yielded a power‐law form of one‐dimensional wave number spectrum of spectral index 2 in a direction transverse to the magnetic field over a scale size range of several km to several tens of m. Equatorial scintillation measurements in the WHF/UHF band which are most sensitive to irregularities of several km to several hundred m are consistent with the in situ spectral results. The backscatter measurements made at Jicamarca at 50 MHz provide an additional measurement of the spectral power at 3m wavelength. Computations are presented for the backscatter intensity expected from irregularities with power law spectrum in the transverse direction but which are infinitely elongated along the magnetic field. The computed intensity is compared with actual backscatter measurements and correlated scintillation observations. It is found that in order to reconcile the backscatter measurements with the simultaneous VHF/UHF scintillation observations a gaussian type cut‐off of the power‐law spectrum is necessary at m wavelengths near the O+ ion gyro‐radius. Copyright 1978 by the American Geophysical Union.