Evidence is given for intense VHF and UHF radar backscatter during equatorial Spread F resulting from irregularities of 1 meter and and 36 cm, respectively. The linear theory for high frequency (&ohgr;>&OHgr;i, where &OHgr;i is the ion gyrofrequency) drift waves, generated by the drift-cyclotron and lower-hybrid-drift instabilities, is presented. This linear theory is set forth as a possible explanation for the occurrence of these irregularities below the ion gyroradius. The maximum growth for these instabilities occurs for kre~1, where k is the wavenumber perpendicular to the magnetic field and re is the electron gyroradius. For these instabilities, the growth rate is &lgr;> (me/mi)1/4&OHgr;i and results in growth times less than a second. For typical equatorial Spread F ionospheric parameters, where (&ngr;ii/&OHgr;i) (kri)2>1 (&ngr;ii is the ion-ion collision frequency, ri is the ion gyroradius), the lower-hybrid-drift instability is dominant.