Dual-frequency coherent backscatter measurements from a fixed volume in the midlatitude E region ionosphere, made simultaneously with two radars operating at significantly different VHF radio frequencies, 144 MHz and 50 MHz, were used to study the scattering cross-section ratios and the spatial spectrum dependence in the 1-m to 3-m wavelength range. To calibrate the measurements, simultaneous aircraft echo intensities observed by the radars during the experiment were used. It was found that the 1-m to 3-m plasma wave scattering cross-section ratios, &Sgr;=&sgr;1m/&sgr;3m, were always below unity, but their values depended strongly on the type of irregularities observed, either type 1 (large phase velocity Farley-Buneman) or type 2 (low phase velocity secondary) waves. Mean values for &Sgr; were near ~0.4 for type 1 echoes and ~0.06 for type 2 echoes, suggesting that secondary waves are more difficult to generate at 1-m than at 3-m wavelength even though type 1 waves are nearly always seen simultaneously at both 50 and 144 MHz. Assuming a negative power law k dependence for the irregularity spatial spectrum, Ik∝k-&bgr;, the spectrum slope &bgr; was found on the average to be about 1.0 and 2.8 for type 1 and type 2 irregularities, respectively, which suggests that the k spectrum is nearly 3 times steeper for type 2 than type 1 waves in the meter wavelength range. These figures are roughly consistent with the predictions of the unified theory of Sudan [1983> for both types of irregularities, but particularly for type 2 waves; for type 1 waves the agreement is not as good, but the theoretical predictions are not as well defined either. ¿ 1999 American Geophysical Union