  Recent advancement in superconducting radio frequency cavity processing
techniques, with diffusion of impurities within the RF penetration depth,
resulted in high quality factor with increase in quality factor with increasing
accelerating gradient. The increase in quality factor is the result of a
decrease in the surface resistance as a result of nonmagnetic impurities doping
and change in electronic density of states. The fundamental understanding of
the dependence of surface resistance on frequency and surface preparation is
still an active area of research. Here, we present the result of RF
measurements of the TEM modes in a coaxial half wave niobium cavity resonating
at frequencies between 0.3-1.3 GHz. The temperature dependence of the surface
resistance was measured between 4.2 K and 1.6 K. The field dependence of the
surface resistance was measured at 2.0 K. The baseline measurements were made
after standard surface preparation by buffered chemical polishing.
