Composite fibers of single walled carbon nanotubes dispersed in poly(methyl methacrylate) and polystyrene are prepared using electrospinning. The single fiber electrical conductivity is measured as a function of the composition of carbon nanotubes. A noncontact method of measuring the carrier mobility at microwave frequency (14 GHz) using bimodal cavity is employed. The mobility measurements indicate lower percolation threshold for mobility compared to electrical conduction. For higher concentrations of carbon nanotubes, the mobility is found to decrease indicating possible carrier-lattice scattering. © 2008 American Institute of Physics.